1 /* 2 * kernel/lockdep.c 3 * 4 * Runtime locking correctness validator 5 * 6 * Started by Ingo Molnar: 7 * 8 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> 9 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com> 10 * 11 * this code maps all the lock dependencies as they occur in a live kernel 12 * and will warn about the following classes of locking bugs: 13 * 14 * - lock inversion scenarios 15 * - circular lock dependencies 16 * - hardirq/softirq safe/unsafe locking bugs 17 * 18 * Bugs are reported even if the current locking scenario does not cause 19 * any deadlock at this point. 20 * 21 * I.e. if anytime in the past two locks were taken in a different order, 22 * even if it happened for another task, even if those were different 23 * locks (but of the same class as this lock), this code will detect it. 24 * 25 * Thanks to Arjan van de Ven for coming up with the initial idea of 26 * mapping lock dependencies runtime. 27 */ 28 #define DISABLE_BRANCH_PROFILING 29 #include <linux/mutex.h> 30 #include <linux/sched.h> 31 #include <linux/delay.h> 32 #include <linux/module.h> 33 #include <linux/proc_fs.h> 34 #include <linux/seq_file.h> 35 #include <linux/spinlock.h> 36 #include <linux/kallsyms.h> 37 #include <linux/interrupt.h> 38 #include <linux/stacktrace.h> 39 #include <linux/debug_locks.h> 40 #include <linux/irqflags.h> 41 #include <linux/utsname.h> 42 #include <linux/hash.h> 43 #include <linux/ftrace.h> 44 #include <linux/stringify.h> 45 #include <linux/bitops.h> 46 #include <linux/gfp.h> 47 #include <linux/kmemcheck.h> 48 49 #include <asm/sections.h> 50 51 #include "lockdep_internals.h" 52 53 #define CREATE_TRACE_POINTS 54 #include <trace/events/lock.h> 55 56 #ifdef CONFIG_PROVE_LOCKING 57 int prove_locking = 1; 58 module_param(prove_locking, int, 0644); 59 #else 60 #define prove_locking 0 61 #endif 62 63 #ifdef CONFIG_LOCK_STAT 64 int lock_stat = 1; 65 module_param(lock_stat, int, 0644); 66 #else 67 #define lock_stat 0 68 #endif 69 70 /* 71 * lockdep_lock: protects the lockdep graph, the hashes and the 72 * class/list/hash allocators. 73 * 74 * This is one of the rare exceptions where it's justified 75 * to use a raw spinlock - we really dont want the spinlock 76 * code to recurse back into the lockdep code... 77 */ 78 static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 79 80 static int graph_lock(void) 81 { 82 arch_spin_lock(&lockdep_lock); 83 /* 84 * Make sure that if another CPU detected a bug while 85 * walking the graph we dont change it (while the other 86 * CPU is busy printing out stuff with the graph lock 87 * dropped already) 88 */ 89 if (!debug_locks) { 90 arch_spin_unlock(&lockdep_lock); 91 return 0; 92 } 93 /* prevent any recursions within lockdep from causing deadlocks */ 94 current->lockdep_recursion++; 95 return 1; 96 } 97 98 static inline int graph_unlock(void) 99 { 100 if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) { 101 /* 102 * The lockdep graph lock isn't locked while we expect it to 103 * be, we're confused now, bye! 104 */ 105 return DEBUG_LOCKS_WARN_ON(1); 106 } 107 108 current->lockdep_recursion--; 109 arch_spin_unlock(&lockdep_lock); 110 return 0; 111 } 112 113 /* 114 * Turn lock debugging off and return with 0 if it was off already, 115 * and also release the graph lock: 116 */ 117 static inline int debug_locks_off_graph_unlock(void) 118 { 119 int ret = debug_locks_off(); 120 121 arch_spin_unlock(&lockdep_lock); 122 123 return ret; 124 } 125 126 static int lockdep_initialized; 127 128 unsigned long nr_list_entries; 129 static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES]; 130 131 /* 132 * All data structures here are protected by the global debug_lock. 133 * 134 * Mutex key structs only get allocated, once during bootup, and never 135 * get freed - this significantly simplifies the debugging code. 136 */ 137 unsigned long nr_lock_classes; 138 static struct lock_class lock_classes[MAX_LOCKDEP_KEYS]; 139 140 static inline struct lock_class *hlock_class(struct held_lock *hlock) 141 { 142 if (!hlock->class_idx) { 143 /* 144 * Someone passed in garbage, we give up. 145 */ 146 DEBUG_LOCKS_WARN_ON(1); 147 return NULL; 148 } 149 return lock_classes + hlock->class_idx - 1; 150 } 151 152 #ifdef CONFIG_LOCK_STAT 153 static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], 154 cpu_lock_stats); 155 156 static inline u64 lockstat_clock(void) 157 { 158 return local_clock(); 159 } 160 161 static int lock_point(unsigned long points[], unsigned long ip) 162 { 163 int i; 164 165 for (i = 0; i < LOCKSTAT_POINTS; i++) { 166 if (points[i] == 0) { 167 points[i] = ip; 168 break; 169 } 170 if (points[i] == ip) 171 break; 172 } 173 174 return i; 175 } 176 177 static void lock_time_inc(struct lock_time *lt, u64 time) 178 { 179 if (time > lt->max) 180 lt->max = time; 181 182 if (time < lt->min || !lt->nr) 183 lt->min = time; 184 185 lt->total += time; 186 lt->nr++; 187 } 188 189 static inline void lock_time_add(struct lock_time *src, struct lock_time *dst) 190 { 191 if (!src->nr) 192 return; 193 194 if (src->max > dst->max) 195 dst->max = src->max; 196 197 if (src->min < dst->min || !dst->nr) 198 dst->min = src->min; 199 200 dst->total += src->total; 201 dst->nr += src->nr; 202 } 203 204 struct lock_class_stats lock_stats(struct lock_class *class) 205 { 206 struct lock_class_stats stats; 207 int cpu, i; 208 209 memset(&stats, 0, sizeof(struct lock_class_stats)); 210 for_each_possible_cpu(cpu) { 211 struct lock_class_stats *pcs = 212 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes]; 213 214 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++) 215 stats.contention_point[i] += pcs->contention_point[i]; 216 217 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++) 218 stats.contending_point[i] += pcs->contending_point[i]; 219 220 lock_time_add(&pcs->read_waittime, &stats.read_waittime); 221 lock_time_add(&pcs->write_waittime, &stats.write_waittime); 222 223 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime); 224 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime); 225 226 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++) 227 stats.bounces[i] += pcs->bounces[i]; 228 } 229 230 return stats; 231 } 232 233 void clear_lock_stats(struct lock_class *class) 234 { 235 int cpu; 236 237 for_each_possible_cpu(cpu) { 238 struct lock_class_stats *cpu_stats = 239 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes]; 240 241 memset(cpu_stats, 0, sizeof(struct lock_class_stats)); 242 } 243 memset(class->contention_point, 0, sizeof(class->contention_point)); 244 memset(class->contending_point, 0, sizeof(class->contending_point)); 245 } 246 247 static struct lock_class_stats *get_lock_stats(struct lock_class *class) 248 { 249 return &get_cpu_var(cpu_lock_stats)[class - lock_classes]; 250 } 251 252 static void put_lock_stats(struct lock_class_stats *stats) 253 { 254 put_cpu_var(cpu_lock_stats); 255 } 256 257 static void lock_release_holdtime(struct held_lock *hlock) 258 { 259 struct lock_class_stats *stats; 260 u64 holdtime; 261 262 if (!lock_stat) 263 return; 264 265 holdtime = lockstat_clock() - hlock->holdtime_stamp; 266 267 stats = get_lock_stats(hlock_class(hlock)); 268 if (hlock->read) 269 lock_time_inc(&stats->read_holdtime, holdtime); 270 else 271 lock_time_inc(&stats->write_holdtime, holdtime); 272 put_lock_stats(stats); 273 } 274 #else 275 static inline void lock_release_holdtime(struct held_lock *hlock) 276 { 277 } 278 #endif 279 280 /* 281 * We keep a global list of all lock classes. The list only grows, 282 * never shrinks. The list is only accessed with the lockdep 283 * spinlock lock held. 284 */ 285 LIST_HEAD(all_lock_classes); 286 287 /* 288 * The lockdep classes are in a hash-table as well, for fast lookup: 289 */ 290 #define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1) 291 #define CLASSHASH_SIZE (1UL << CLASSHASH_BITS) 292 #define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS) 293 #define classhashentry(key) (classhash_table + __classhashfn((key))) 294 295 static struct list_head classhash_table[CLASSHASH_SIZE]; 296 297 /* 298 * We put the lock dependency chains into a hash-table as well, to cache 299 * their existence: 300 */ 301 #define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1) 302 #define CHAINHASH_SIZE (1UL << CHAINHASH_BITS) 303 #define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS) 304 #define chainhashentry(chain) (chainhash_table + __chainhashfn((chain))) 305 306 static struct list_head chainhash_table[CHAINHASH_SIZE]; 307 308 /* 309 * The hash key of the lock dependency chains is a hash itself too: 310 * it's a hash of all locks taken up to that lock, including that lock. 311 * It's a 64-bit hash, because it's important for the keys to be 312 * unique. 313 */ 314 #define iterate_chain_key(key1, key2) \ 315 (((key1) << MAX_LOCKDEP_KEYS_BITS) ^ \ 316 ((key1) >> (64-MAX_LOCKDEP_KEYS_BITS)) ^ \ 317 (key2)) 318 319 void lockdep_off(void) 320 { 321 current->lockdep_recursion++; 322 } 323 EXPORT_SYMBOL(lockdep_off); 324 325 void lockdep_on(void) 326 { 327 current->lockdep_recursion--; 328 } 329 EXPORT_SYMBOL(lockdep_on); 330 331 /* 332 * Debugging switches: 333 */ 334 335 #define VERBOSE 0 336 #define VERY_VERBOSE 0 337 338 #if VERBOSE 339 # define HARDIRQ_VERBOSE 1 340 # define SOFTIRQ_VERBOSE 1 341 # define RECLAIM_VERBOSE 1 342 #else 343 # define HARDIRQ_VERBOSE 0 344 # define SOFTIRQ_VERBOSE 0 345 # define RECLAIM_VERBOSE 0 346 #endif 347 348 #if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE 349 /* 350 * Quick filtering for interesting events: 351 */ 352 static int class_filter(struct lock_class *class) 353 { 354 #if 0 355 /* Example */ 356 if (class->name_version == 1 && 357 !strcmp(class->name, "lockname")) 358 return 1; 359 if (class->name_version == 1 && 360 !strcmp(class->name, "&struct->lockfield")) 361 return 1; 362 #endif 363 /* Filter everything else. 1 would be to allow everything else */ 364 return 0; 365 } 366 #endif 367 368 static int verbose(struct lock_class *class) 369 { 370 #if VERBOSE 371 return class_filter(class); 372 #endif 373 return 0; 374 } 375 376 /* 377 * Stack-trace: tightly packed array of stack backtrace 378 * addresses. Protected by the graph_lock. 379 */ 380 unsigned long nr_stack_trace_entries; 381 static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES]; 382 383 static void print_lockdep_off(const char *bug_msg) 384 { 385 printk(KERN_DEBUG "%s\n", bug_msg); 386 printk(KERN_DEBUG "turning off the locking correctness validator.\n"); 387 #ifdef CONFIG_LOCK_STAT 388 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n"); 389 #endif 390 } 391 392 static int save_trace(struct stack_trace *trace) 393 { 394 trace->nr_entries = 0; 395 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries; 396 trace->entries = stack_trace + nr_stack_trace_entries; 397 398 trace->skip = 3; 399 400 save_stack_trace(trace); 401 402 /* 403 * Some daft arches put -1 at the end to indicate its a full trace. 404 * 405 * <rant> this is buggy anyway, since it takes a whole extra entry so a 406 * complete trace that maxes out the entries provided will be reported 407 * as incomplete, friggin useless </rant> 408 */ 409 if (trace->nr_entries != 0 && 410 trace->entries[trace->nr_entries-1] == ULONG_MAX) 411 trace->nr_entries--; 412 413 trace->max_entries = trace->nr_entries; 414 415 nr_stack_trace_entries += trace->nr_entries; 416 417 if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) { 418 if (!debug_locks_off_graph_unlock()) 419 return 0; 420 421 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!"); 422 dump_stack(); 423 424 return 0; 425 } 426 427 return 1; 428 } 429 430 unsigned int nr_hardirq_chains; 431 unsigned int nr_softirq_chains; 432 unsigned int nr_process_chains; 433 unsigned int max_lockdep_depth; 434 435 #ifdef CONFIG_DEBUG_LOCKDEP 436 /* 437 * We cannot printk in early bootup code. Not even early_printk() 438 * might work. So we mark any initialization errors and printk 439 * about it later on, in lockdep_info(). 440 */ 441 static int lockdep_init_error; 442 static const char *lock_init_error; 443 static unsigned long lockdep_init_trace_data[20]; 444 static struct stack_trace lockdep_init_trace = { 445 .max_entries = ARRAY_SIZE(lockdep_init_trace_data), 446 .entries = lockdep_init_trace_data, 447 }; 448 449 /* 450 * Various lockdep statistics: 451 */ 452 DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats); 453 #endif 454 455 /* 456 * Locking printouts: 457 */ 458 459 #define __USAGE(__STATE) \ 460 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \ 461 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \ 462 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\ 463 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R", 464 465 static const char *usage_str[] = 466 { 467 #define LOCKDEP_STATE(__STATE) __USAGE(__STATE) 468 #include "lockdep_states.h" 469 #undef LOCKDEP_STATE 470 [LOCK_USED] = "INITIAL USE", 471 }; 472 473 const char * __get_key_name(struct lockdep_subclass_key *key, char *str) 474 { 475 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str); 476 } 477 478 static inline unsigned long lock_flag(enum lock_usage_bit bit) 479 { 480 return 1UL << bit; 481 } 482 483 static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit) 484 { 485 char c = '.'; 486 487 if (class->usage_mask & lock_flag(bit + 2)) 488 c = '+'; 489 if (class->usage_mask & lock_flag(bit)) { 490 c = '-'; 491 if (class->usage_mask & lock_flag(bit + 2)) 492 c = '?'; 493 } 494 495 return c; 496 } 497 498 void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS]) 499 { 500 int i = 0; 501 502 #define LOCKDEP_STATE(__STATE) \ 503 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \ 504 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ); 505 #include "lockdep_states.h" 506 #undef LOCKDEP_STATE 507 508 usage[i] = '\0'; 509 } 510 511 static void __print_lock_name(struct lock_class *class) 512 { 513 char str[KSYM_NAME_LEN]; 514 const char *name; 515 516 name = class->name; 517 if (!name) { 518 name = __get_key_name(class->key, str); 519 printk("%s", name); 520 } else { 521 printk("%s", name); 522 if (class->name_version > 1) 523 printk("#%d", class->name_version); 524 if (class->subclass) 525 printk("/%d", class->subclass); 526 } 527 } 528 529 static void print_lock_name(struct lock_class *class) 530 { 531 char usage[LOCK_USAGE_CHARS]; 532 533 get_usage_chars(class, usage); 534 535 printk(" ("); 536 __print_lock_name(class); 537 printk("){%s}", usage); 538 } 539 540 static void print_lockdep_cache(struct lockdep_map *lock) 541 { 542 const char *name; 543 char str[KSYM_NAME_LEN]; 544 545 name = lock->name; 546 if (!name) 547 name = __get_key_name(lock->key->subkeys, str); 548 549 printk("%s", name); 550 } 551 552 static void print_lock(struct held_lock *hlock) 553 { 554 /* 555 * We can be called locklessly through debug_show_all_locks() so be 556 * extra careful, the hlock might have been released and cleared. 557 */ 558 unsigned int class_idx = hlock->class_idx; 559 560 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfields: */ 561 barrier(); 562 563 if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) { 564 printk("<RELEASED>\n"); 565 return; 566 } 567 568 print_lock_name(lock_classes + class_idx - 1); 569 printk(", at: "); 570 print_ip_sym(hlock->acquire_ip); 571 } 572 573 static void lockdep_print_held_locks(struct task_struct *curr) 574 { 575 int i, depth = curr->lockdep_depth; 576 577 if (!depth) { 578 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr)); 579 return; 580 } 581 printk("%d lock%s held by %s/%d:\n", 582 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr)); 583 584 for (i = 0; i < depth; i++) { 585 printk(" #%d: ", i); 586 print_lock(curr->held_locks + i); 587 } 588 } 589 590 static void print_kernel_ident(void) 591 { 592 printk("%s %.*s %s\n", init_utsname()->release, 593 (int)strcspn(init_utsname()->version, " "), 594 init_utsname()->version, 595 print_tainted()); 596 } 597 598 static int very_verbose(struct lock_class *class) 599 { 600 #if VERY_VERBOSE 601 return class_filter(class); 602 #endif 603 return 0; 604 } 605 606 /* 607 * Is this the address of a static object: 608 */ 609 #ifdef __KERNEL__ 610 static int static_obj(void *obj) 611 { 612 unsigned long start = (unsigned long) &_stext, 613 end = (unsigned long) &_end, 614 addr = (unsigned long) obj; 615 616 /* 617 * static variable? 618 */ 619 if ((addr >= start) && (addr < end)) 620 return 1; 621 622 if (arch_is_kernel_data(addr)) 623 return 1; 624 625 /* 626 * in-kernel percpu var? 627 */ 628 if (is_kernel_percpu_address(addr)) 629 return 1; 630 631 /* 632 * module static or percpu var? 633 */ 634 return is_module_address(addr) || is_module_percpu_address(addr); 635 } 636 #endif 637 638 /* 639 * To make lock name printouts unique, we calculate a unique 640 * class->name_version generation counter: 641 */ 642 static int count_matching_names(struct lock_class *new_class) 643 { 644 struct lock_class *class; 645 int count = 0; 646 647 if (!new_class->name) 648 return 0; 649 650 list_for_each_entry_rcu(class, &all_lock_classes, lock_entry) { 651 if (new_class->key - new_class->subclass == class->key) 652 return class->name_version; 653 if (class->name && !strcmp(class->name, new_class->name)) 654 count = max(count, class->name_version); 655 } 656 657 return count + 1; 658 } 659 660 /* 661 * Register a lock's class in the hash-table, if the class is not present 662 * yet. Otherwise we look it up. We cache the result in the lock object 663 * itself, so actual lookup of the hash should be once per lock object. 664 */ 665 static inline struct lock_class * 666 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass) 667 { 668 struct lockdep_subclass_key *key; 669 struct list_head *hash_head; 670 struct lock_class *class; 671 672 #ifdef CONFIG_DEBUG_LOCKDEP 673 /* 674 * If the architecture calls into lockdep before initializing 675 * the hashes then we'll warn about it later. (we cannot printk 676 * right now) 677 */ 678 if (unlikely(!lockdep_initialized)) { 679 lockdep_init(); 680 lockdep_init_error = 1; 681 lock_init_error = lock->name; 682 save_stack_trace(&lockdep_init_trace); 683 } 684 #endif 685 686 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) { 687 debug_locks_off(); 688 printk(KERN_ERR 689 "BUG: looking up invalid subclass: %u\n", subclass); 690 printk(KERN_ERR 691 "turning off the locking correctness validator.\n"); 692 dump_stack(); 693 return NULL; 694 } 695 696 /* 697 * Static locks do not have their class-keys yet - for them the key 698 * is the lock object itself: 699 */ 700 if (unlikely(!lock->key)) 701 lock->key = (void *)lock; 702 703 /* 704 * NOTE: the class-key must be unique. For dynamic locks, a static 705 * lock_class_key variable is passed in through the mutex_init() 706 * (or spin_lock_init()) call - which acts as the key. For static 707 * locks we use the lock object itself as the key. 708 */ 709 BUILD_BUG_ON(sizeof(struct lock_class_key) > 710 sizeof(struct lockdep_map)); 711 712 key = lock->key->subkeys + subclass; 713 714 hash_head = classhashentry(key); 715 716 /* 717 * We do an RCU walk of the hash, see lockdep_free_key_range(). 718 */ 719 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) 720 return NULL; 721 722 list_for_each_entry_rcu(class, hash_head, hash_entry) { 723 if (class->key == key) { 724 /* 725 * Huh! same key, different name? Did someone trample 726 * on some memory? We're most confused. 727 */ 728 WARN_ON_ONCE(class->name != lock->name); 729 return class; 730 } 731 } 732 733 return NULL; 734 } 735 736 /* 737 * Register a lock's class in the hash-table, if the class is not present 738 * yet. Otherwise we look it up. We cache the result in the lock object 739 * itself, so actual lookup of the hash should be once per lock object. 740 */ 741 static inline struct lock_class * 742 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) 743 { 744 struct lockdep_subclass_key *key; 745 struct list_head *hash_head; 746 struct lock_class *class; 747 748 DEBUG_LOCKS_WARN_ON(!irqs_disabled()); 749 750 class = look_up_lock_class(lock, subclass); 751 if (likely(class)) 752 goto out_set_class_cache; 753 754 /* 755 * Debug-check: all keys must be persistent! 756 */ 757 if (!static_obj(lock->key)) { 758 debug_locks_off(); 759 printk("INFO: trying to register non-static key.\n"); 760 printk("the code is fine but needs lockdep annotation.\n"); 761 printk("turning off the locking correctness validator.\n"); 762 dump_stack(); 763 764 return NULL; 765 } 766 767 key = lock->key->subkeys + subclass; 768 hash_head = classhashentry(key); 769 770 if (!graph_lock()) { 771 return NULL; 772 } 773 /* 774 * We have to do the hash-walk again, to avoid races 775 * with another CPU: 776 */ 777 list_for_each_entry_rcu(class, hash_head, hash_entry) { 778 if (class->key == key) 779 goto out_unlock_set; 780 } 781 782 /* 783 * Allocate a new key from the static array, and add it to 784 * the hash: 785 */ 786 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) { 787 if (!debug_locks_off_graph_unlock()) { 788 return NULL; 789 } 790 791 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!"); 792 dump_stack(); 793 return NULL; 794 } 795 class = lock_classes + nr_lock_classes++; 796 debug_atomic_inc(nr_unused_locks); 797 class->key = key; 798 class->name = lock->name; 799 class->subclass = subclass; 800 INIT_LIST_HEAD(&class->lock_entry); 801 INIT_LIST_HEAD(&class->locks_before); 802 INIT_LIST_HEAD(&class->locks_after); 803 class->name_version = count_matching_names(class); 804 /* 805 * We use RCU's safe list-add method to make 806 * parallel walking of the hash-list safe: 807 */ 808 list_add_tail_rcu(&class->hash_entry, hash_head); 809 /* 810 * Add it to the global list of classes: 811 */ 812 list_add_tail_rcu(&class->lock_entry, &all_lock_classes); 813 814 if (verbose(class)) { 815 graph_unlock(); 816 817 printk("\nnew class %p: %s", class->key, class->name); 818 if (class->name_version > 1) 819 printk("#%d", class->name_version); 820 printk("\n"); 821 dump_stack(); 822 823 if (!graph_lock()) { 824 return NULL; 825 } 826 } 827 out_unlock_set: 828 graph_unlock(); 829 830 out_set_class_cache: 831 if (!subclass || force) 832 lock->class_cache[0] = class; 833 else if (subclass < NR_LOCKDEP_CACHING_CLASSES) 834 lock->class_cache[subclass] = class; 835 836 /* 837 * Hash collision, did we smoke some? We found a class with a matching 838 * hash but the subclass -- which is hashed in -- didn't match. 839 */ 840 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass)) 841 return NULL; 842 843 return class; 844 } 845 846 #ifdef CONFIG_PROVE_LOCKING 847 /* 848 * Allocate a lockdep entry. (assumes the graph_lock held, returns 849 * with NULL on failure) 850 */ 851 static struct lock_list *alloc_list_entry(void) 852 { 853 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) { 854 if (!debug_locks_off_graph_unlock()) 855 return NULL; 856 857 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!"); 858 dump_stack(); 859 return NULL; 860 } 861 return list_entries + nr_list_entries++; 862 } 863 864 /* 865 * Add a new dependency to the head of the list: 866 */ 867 static int add_lock_to_list(struct lock_class *class, struct lock_class *this, 868 struct list_head *head, unsigned long ip, 869 int distance, struct stack_trace *trace) 870 { 871 struct lock_list *entry; 872 /* 873 * Lock not present yet - get a new dependency struct and 874 * add it to the list: 875 */ 876 entry = alloc_list_entry(); 877 if (!entry) 878 return 0; 879 880 entry->class = this; 881 entry->distance = distance; 882 entry->trace = *trace; 883 /* 884 * Both allocation and removal are done under the graph lock; but 885 * iteration is under RCU-sched; see look_up_lock_class() and 886 * lockdep_free_key_range(). 887 */ 888 list_add_tail_rcu(&entry->entry, head); 889 890 return 1; 891 } 892 893 /* 894 * For good efficiency of modular, we use power of 2 895 */ 896 #define MAX_CIRCULAR_QUEUE_SIZE 4096UL 897 #define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1) 898 899 /* 900 * The circular_queue and helpers is used to implement the 901 * breadth-first search(BFS)algorithem, by which we can build 902 * the shortest path from the next lock to be acquired to the 903 * previous held lock if there is a circular between them. 904 */ 905 struct circular_queue { 906 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE]; 907 unsigned int front, rear; 908 }; 909 910 static struct circular_queue lock_cq; 911 912 unsigned int max_bfs_queue_depth; 913 914 static unsigned int lockdep_dependency_gen_id; 915 916 static inline void __cq_init(struct circular_queue *cq) 917 { 918 cq->front = cq->rear = 0; 919 lockdep_dependency_gen_id++; 920 } 921 922 static inline int __cq_empty(struct circular_queue *cq) 923 { 924 return (cq->front == cq->rear); 925 } 926 927 static inline int __cq_full(struct circular_queue *cq) 928 { 929 return ((cq->rear + 1) & CQ_MASK) == cq->front; 930 } 931 932 static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem) 933 { 934 if (__cq_full(cq)) 935 return -1; 936 937 cq->element[cq->rear] = elem; 938 cq->rear = (cq->rear + 1) & CQ_MASK; 939 return 0; 940 } 941 942 static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem) 943 { 944 if (__cq_empty(cq)) 945 return -1; 946 947 *elem = cq->element[cq->front]; 948 cq->front = (cq->front + 1) & CQ_MASK; 949 return 0; 950 } 951 952 static inline unsigned int __cq_get_elem_count(struct circular_queue *cq) 953 { 954 return (cq->rear - cq->front) & CQ_MASK; 955 } 956 957 static inline void mark_lock_accessed(struct lock_list *lock, 958 struct lock_list *parent) 959 { 960 unsigned long nr; 961 962 nr = lock - list_entries; 963 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */ 964 lock->parent = parent; 965 lock->class->dep_gen_id = lockdep_dependency_gen_id; 966 } 967 968 static inline unsigned long lock_accessed(struct lock_list *lock) 969 { 970 unsigned long nr; 971 972 nr = lock - list_entries; 973 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */ 974 return lock->class->dep_gen_id == lockdep_dependency_gen_id; 975 } 976 977 static inline struct lock_list *get_lock_parent(struct lock_list *child) 978 { 979 return child->parent; 980 } 981 982 static inline int get_lock_depth(struct lock_list *child) 983 { 984 int depth = 0; 985 struct lock_list *parent; 986 987 while ((parent = get_lock_parent(child))) { 988 child = parent; 989 depth++; 990 } 991 return depth; 992 } 993 994 static int __bfs(struct lock_list *source_entry, 995 void *data, 996 int (*match)(struct lock_list *entry, void *data), 997 struct lock_list **target_entry, 998 int forward) 999 { 1000 struct lock_list *entry; 1001 struct list_head *head; 1002 struct circular_queue *cq = &lock_cq; 1003 int ret = 1; 1004 1005 if (match(source_entry, data)) { 1006 *target_entry = source_entry; 1007 ret = 0; 1008 goto exit; 1009 } 1010 1011 if (forward) 1012 head = &source_entry->class->locks_after; 1013 else 1014 head = &source_entry->class->locks_before; 1015 1016 if (list_empty(head)) 1017 goto exit; 1018 1019 __cq_init(cq); 1020 __cq_enqueue(cq, (unsigned long)source_entry); 1021 1022 while (!__cq_empty(cq)) { 1023 struct lock_list *lock; 1024 1025 __cq_dequeue(cq, (unsigned long *)&lock); 1026 1027 if (!lock->class) { 1028 ret = -2; 1029 goto exit; 1030 } 1031 1032 if (forward) 1033 head = &lock->class->locks_after; 1034 else 1035 head = &lock->class->locks_before; 1036 1037 DEBUG_LOCKS_WARN_ON(!irqs_disabled()); 1038 1039 list_for_each_entry_rcu(entry, head, entry) { 1040 if (!lock_accessed(entry)) { 1041 unsigned int cq_depth; 1042 mark_lock_accessed(entry, lock); 1043 if (match(entry, data)) { 1044 *target_entry = entry; 1045 ret = 0; 1046 goto exit; 1047 } 1048 1049 if (__cq_enqueue(cq, (unsigned long)entry)) { 1050 ret = -1; 1051 goto exit; 1052 } 1053 cq_depth = __cq_get_elem_count(cq); 1054 if (max_bfs_queue_depth < cq_depth) 1055 max_bfs_queue_depth = cq_depth; 1056 } 1057 } 1058 } 1059 exit: 1060 return ret; 1061 } 1062 1063 static inline int __bfs_forwards(struct lock_list *src_entry, 1064 void *data, 1065 int (*match)(struct lock_list *entry, void *data), 1066 struct lock_list **target_entry) 1067 { 1068 return __bfs(src_entry, data, match, target_entry, 1); 1069 1070 } 1071 1072 static inline int __bfs_backwards(struct lock_list *src_entry, 1073 void *data, 1074 int (*match)(struct lock_list *entry, void *data), 1075 struct lock_list **target_entry) 1076 { 1077 return __bfs(src_entry, data, match, target_entry, 0); 1078 1079 } 1080 1081 /* 1082 * Recursive, forwards-direction lock-dependency checking, used for 1083 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe 1084 * checking. 1085 */ 1086 1087 /* 1088 * Print a dependency chain entry (this is only done when a deadlock 1089 * has been detected): 1090 */ 1091 static noinline int 1092 print_circular_bug_entry(struct lock_list *target, int depth) 1093 { 1094 if (debug_locks_silent) 1095 return 0; 1096 printk("\n-> #%u", depth); 1097 print_lock_name(target->class); 1098 printk(":\n"); 1099 print_stack_trace(&target->trace, 6); 1100 1101 return 0; 1102 } 1103 1104 static void 1105 print_circular_lock_scenario(struct held_lock *src, 1106 struct held_lock *tgt, 1107 struct lock_list *prt) 1108 { 1109 struct lock_class *source = hlock_class(src); 1110 struct lock_class *target = hlock_class(tgt); 1111 struct lock_class *parent = prt->class; 1112 1113 /* 1114 * A direct locking problem where unsafe_class lock is taken 1115 * directly by safe_class lock, then all we need to show 1116 * is the deadlock scenario, as it is obvious that the 1117 * unsafe lock is taken under the safe lock. 1118 * 1119 * But if there is a chain instead, where the safe lock takes 1120 * an intermediate lock (middle_class) where this lock is 1121 * not the same as the safe lock, then the lock chain is 1122 * used to describe the problem. Otherwise we would need 1123 * to show a different CPU case for each link in the chain 1124 * from the safe_class lock to the unsafe_class lock. 1125 */ 1126 if (parent != source) { 1127 printk("Chain exists of:\n "); 1128 __print_lock_name(source); 1129 printk(" --> "); 1130 __print_lock_name(parent); 1131 printk(" --> "); 1132 __print_lock_name(target); 1133 printk("\n\n"); 1134 } 1135 1136 printk(" Possible unsafe locking scenario:\n\n"); 1137 printk(" CPU0 CPU1\n"); 1138 printk(" ---- ----\n"); 1139 printk(" lock("); 1140 __print_lock_name(target); 1141 printk(");\n"); 1142 printk(" lock("); 1143 __print_lock_name(parent); 1144 printk(");\n"); 1145 printk(" lock("); 1146 __print_lock_name(target); 1147 printk(");\n"); 1148 printk(" lock("); 1149 __print_lock_name(source); 1150 printk(");\n"); 1151 printk("\n *** DEADLOCK ***\n\n"); 1152 } 1153 1154 /* 1155 * When a circular dependency is detected, print the 1156 * header first: 1157 */ 1158 static noinline int 1159 print_circular_bug_header(struct lock_list *entry, unsigned int depth, 1160 struct held_lock *check_src, 1161 struct held_lock *check_tgt) 1162 { 1163 struct task_struct *curr = current; 1164 1165 if (debug_locks_silent) 1166 return 0; 1167 1168 printk("\n"); 1169 printk("======================================================\n"); 1170 printk("[ INFO: possible circular locking dependency detected ]\n"); 1171 print_kernel_ident(); 1172 printk("-------------------------------------------------------\n"); 1173 printk("%s/%d is trying to acquire lock:\n", 1174 curr->comm, task_pid_nr(curr)); 1175 print_lock(check_src); 1176 printk("\nbut task is already holding lock:\n"); 1177 print_lock(check_tgt); 1178 printk("\nwhich lock already depends on the new lock.\n\n"); 1179 printk("\nthe existing dependency chain (in reverse order) is:\n"); 1180 1181 print_circular_bug_entry(entry, depth); 1182 1183 return 0; 1184 } 1185 1186 static inline int class_equal(struct lock_list *entry, void *data) 1187 { 1188 return entry->class == data; 1189 } 1190 1191 static noinline int print_circular_bug(struct lock_list *this, 1192 struct lock_list *target, 1193 struct held_lock *check_src, 1194 struct held_lock *check_tgt) 1195 { 1196 struct task_struct *curr = current; 1197 struct lock_list *parent; 1198 struct lock_list *first_parent; 1199 int depth; 1200 1201 if (!debug_locks_off_graph_unlock() || debug_locks_silent) 1202 return 0; 1203 1204 if (!save_trace(&this->trace)) 1205 return 0; 1206 1207 depth = get_lock_depth(target); 1208 1209 print_circular_bug_header(target, depth, check_src, check_tgt); 1210 1211 parent = get_lock_parent(target); 1212 first_parent = parent; 1213 1214 while (parent) { 1215 print_circular_bug_entry(parent, --depth); 1216 parent = get_lock_parent(parent); 1217 } 1218 1219 printk("\nother info that might help us debug this:\n\n"); 1220 print_circular_lock_scenario(check_src, check_tgt, 1221 first_parent); 1222 1223 lockdep_print_held_locks(curr); 1224 1225 printk("\nstack backtrace:\n"); 1226 dump_stack(); 1227 1228 return 0; 1229 } 1230 1231 static noinline int print_bfs_bug(int ret) 1232 { 1233 if (!debug_locks_off_graph_unlock()) 1234 return 0; 1235 1236 /* 1237 * Breadth-first-search failed, graph got corrupted? 1238 */ 1239 WARN(1, "lockdep bfs error:%d\n", ret); 1240 1241 return 0; 1242 } 1243 1244 static int noop_count(struct lock_list *entry, void *data) 1245 { 1246 (*(unsigned long *)data)++; 1247 return 0; 1248 } 1249 1250 static unsigned long __lockdep_count_forward_deps(struct lock_list *this) 1251 { 1252 unsigned long count = 0; 1253 struct lock_list *uninitialized_var(target_entry); 1254 1255 __bfs_forwards(this, (void *)&count, noop_count, &target_entry); 1256 1257 return count; 1258 } 1259 unsigned long lockdep_count_forward_deps(struct lock_class *class) 1260 { 1261 unsigned long ret, flags; 1262 struct lock_list this; 1263 1264 this.parent = NULL; 1265 this.class = class; 1266 1267 local_irq_save(flags); 1268 arch_spin_lock(&lockdep_lock); 1269 ret = __lockdep_count_forward_deps(&this); 1270 arch_spin_unlock(&lockdep_lock); 1271 local_irq_restore(flags); 1272 1273 return ret; 1274 } 1275 1276 static unsigned long __lockdep_count_backward_deps(struct lock_list *this) 1277 { 1278 unsigned long count = 0; 1279 struct lock_list *uninitialized_var(target_entry); 1280 1281 __bfs_backwards(this, (void *)&count, noop_count, &target_entry); 1282 1283 return count; 1284 } 1285 1286 unsigned long lockdep_count_backward_deps(struct lock_class *class) 1287 { 1288 unsigned long ret, flags; 1289 struct lock_list this; 1290 1291 this.parent = NULL; 1292 this.class = class; 1293 1294 local_irq_save(flags); 1295 arch_spin_lock(&lockdep_lock); 1296 ret = __lockdep_count_backward_deps(&this); 1297 arch_spin_unlock(&lockdep_lock); 1298 local_irq_restore(flags); 1299 1300 return ret; 1301 } 1302 1303 /* 1304 * Prove that the dependency graph starting at <entry> can not 1305 * lead to <target>. Print an error and return 0 if it does. 1306 */ 1307 static noinline int 1308 check_noncircular(struct lock_list *root, struct lock_class *target, 1309 struct lock_list **target_entry) 1310 { 1311 int result; 1312 1313 debug_atomic_inc(nr_cyclic_checks); 1314 1315 result = __bfs_forwards(root, target, class_equal, target_entry); 1316 1317 return result; 1318 } 1319 1320 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) 1321 /* 1322 * Forwards and backwards subgraph searching, for the purposes of 1323 * proving that two subgraphs can be connected by a new dependency 1324 * without creating any illegal irq-safe -> irq-unsafe lock dependency. 1325 */ 1326 1327 static inline int usage_match(struct lock_list *entry, void *bit) 1328 { 1329 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit); 1330 } 1331 1332 1333 1334 /* 1335 * Find a node in the forwards-direction dependency sub-graph starting 1336 * at @root->class that matches @bit. 1337 * 1338 * Return 0 if such a node exists in the subgraph, and put that node 1339 * into *@target_entry. 1340 * 1341 * Return 1 otherwise and keep *@target_entry unchanged. 1342 * Return <0 on error. 1343 */ 1344 static int 1345 find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit, 1346 struct lock_list **target_entry) 1347 { 1348 int result; 1349 1350 debug_atomic_inc(nr_find_usage_forwards_checks); 1351 1352 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry); 1353 1354 return result; 1355 } 1356 1357 /* 1358 * Find a node in the backwards-direction dependency sub-graph starting 1359 * at @root->class that matches @bit. 1360 * 1361 * Return 0 if such a node exists in the subgraph, and put that node 1362 * into *@target_entry. 1363 * 1364 * Return 1 otherwise and keep *@target_entry unchanged. 1365 * Return <0 on error. 1366 */ 1367 static int 1368 find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit, 1369 struct lock_list **target_entry) 1370 { 1371 int result; 1372 1373 debug_atomic_inc(nr_find_usage_backwards_checks); 1374 1375 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry); 1376 1377 return result; 1378 } 1379 1380 static void print_lock_class_header(struct lock_class *class, int depth) 1381 { 1382 int bit; 1383 1384 printk("%*s->", depth, ""); 1385 print_lock_name(class); 1386 printk(" ops: %lu", class->ops); 1387 printk(" {\n"); 1388 1389 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) { 1390 if (class->usage_mask & (1 << bit)) { 1391 int len = depth; 1392 1393 len += printk("%*s %s", depth, "", usage_str[bit]); 1394 len += printk(" at:\n"); 1395 print_stack_trace(class->usage_traces + bit, len); 1396 } 1397 } 1398 printk("%*s }\n", depth, ""); 1399 1400 printk("%*s ... key at: ",depth,""); 1401 print_ip_sym((unsigned long)class->key); 1402 } 1403 1404 /* 1405 * printk the shortest lock dependencies from @start to @end in reverse order: 1406 */ 1407 static void __used 1408 print_shortest_lock_dependencies(struct lock_list *leaf, 1409 struct lock_list *root) 1410 { 1411 struct lock_list *entry = leaf; 1412 int depth; 1413 1414 /*compute depth from generated tree by BFS*/ 1415 depth = get_lock_depth(leaf); 1416 1417 do { 1418 print_lock_class_header(entry->class, depth); 1419 printk("%*s ... acquired at:\n", depth, ""); 1420 print_stack_trace(&entry->trace, 2); 1421 printk("\n"); 1422 1423 if (depth == 0 && (entry != root)) { 1424 printk("lockdep:%s bad path found in chain graph\n", __func__); 1425 break; 1426 } 1427 1428 entry = get_lock_parent(entry); 1429 depth--; 1430 } while (entry && (depth >= 0)); 1431 1432 return; 1433 } 1434 1435 static void 1436 print_irq_lock_scenario(struct lock_list *safe_entry, 1437 struct lock_list *unsafe_entry, 1438 struct lock_class *prev_class, 1439 struct lock_class *next_class) 1440 { 1441 struct lock_class *safe_class = safe_entry->class; 1442 struct lock_class *unsafe_class = unsafe_entry->class; 1443 struct lock_class *middle_class = prev_class; 1444 1445 if (middle_class == safe_class) 1446 middle_class = next_class; 1447 1448 /* 1449 * A direct locking problem where unsafe_class lock is taken 1450 * directly by safe_class lock, then all we need to show 1451 * is the deadlock scenario, as it is obvious that the 1452 * unsafe lock is taken under the safe lock. 1453 * 1454 * But if there is a chain instead, where the safe lock takes 1455 * an intermediate lock (middle_class) where this lock is 1456 * not the same as the safe lock, then the lock chain is 1457 * used to describe the problem. Otherwise we would need 1458 * to show a different CPU case for each link in the chain 1459 * from the safe_class lock to the unsafe_class lock. 1460 */ 1461 if (middle_class != unsafe_class) { 1462 printk("Chain exists of:\n "); 1463 __print_lock_name(safe_class); 1464 printk(" --> "); 1465 __print_lock_name(middle_class); 1466 printk(" --> "); 1467 __print_lock_name(unsafe_class); 1468 printk("\n\n"); 1469 } 1470 1471 printk(" Possible interrupt unsafe locking scenario:\n\n"); 1472 printk(" CPU0 CPU1\n"); 1473 printk(" ---- ----\n"); 1474 printk(" lock("); 1475 __print_lock_name(unsafe_class); 1476 printk(");\n"); 1477 printk(" local_irq_disable();\n"); 1478 printk(" lock("); 1479 __print_lock_name(safe_class); 1480 printk(");\n"); 1481 printk(" lock("); 1482 __print_lock_name(middle_class); 1483 printk(");\n"); 1484 printk(" <Interrupt>\n"); 1485 printk(" lock("); 1486 __print_lock_name(safe_class); 1487 printk(");\n"); 1488 printk("\n *** DEADLOCK ***\n\n"); 1489 } 1490 1491 static int 1492 print_bad_irq_dependency(struct task_struct *curr, 1493 struct lock_list *prev_root, 1494 struct lock_list *next_root, 1495 struct lock_list *backwards_entry, 1496 struct lock_list *forwards_entry, 1497 struct held_lock *prev, 1498 struct held_lock *next, 1499 enum lock_usage_bit bit1, 1500 enum lock_usage_bit bit2, 1501 const char *irqclass) 1502 { 1503 if (!debug_locks_off_graph_unlock() || debug_locks_silent) 1504 return 0; 1505 1506 printk("\n"); 1507 printk("======================================================\n"); 1508 printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n", 1509 irqclass, irqclass); 1510 print_kernel_ident(); 1511 printk("------------------------------------------------------\n"); 1512 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n", 1513 curr->comm, task_pid_nr(curr), 1514 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT, 1515 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT, 1516 curr->hardirqs_enabled, 1517 curr->softirqs_enabled); 1518 print_lock(next); 1519 1520 printk("\nand this task is already holding:\n"); 1521 print_lock(prev); 1522 printk("which would create a new lock dependency:\n"); 1523 print_lock_name(hlock_class(prev)); 1524 printk(" ->"); 1525 print_lock_name(hlock_class(next)); 1526 printk("\n"); 1527 1528 printk("\nbut this new dependency connects a %s-irq-safe lock:\n", 1529 irqclass); 1530 print_lock_name(backwards_entry->class); 1531 printk("\n... which became %s-irq-safe at:\n", irqclass); 1532 1533 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1); 1534 1535 printk("\nto a %s-irq-unsafe lock:\n", irqclass); 1536 print_lock_name(forwards_entry->class); 1537 printk("\n... which became %s-irq-unsafe at:\n", irqclass); 1538 printk("..."); 1539 1540 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1); 1541 1542 printk("\nother info that might help us debug this:\n\n"); 1543 print_irq_lock_scenario(backwards_entry, forwards_entry, 1544 hlock_class(prev), hlock_class(next)); 1545 1546 lockdep_print_held_locks(curr); 1547 1548 printk("\nthe dependencies between %s-irq-safe lock", irqclass); 1549 printk(" and the holding lock:\n"); 1550 if (!save_trace(&prev_root->trace)) 1551 return 0; 1552 print_shortest_lock_dependencies(backwards_entry, prev_root); 1553 1554 printk("\nthe dependencies between the lock to be acquired"); 1555 printk(" and %s-irq-unsafe lock:\n", irqclass); 1556 if (!save_trace(&next_root->trace)) 1557 return 0; 1558 print_shortest_lock_dependencies(forwards_entry, next_root); 1559 1560 printk("\nstack backtrace:\n"); 1561 dump_stack(); 1562 1563 return 0; 1564 } 1565 1566 static int 1567 check_usage(struct task_struct *curr, struct held_lock *prev, 1568 struct held_lock *next, enum lock_usage_bit bit_backwards, 1569 enum lock_usage_bit bit_forwards, const char *irqclass) 1570 { 1571 int ret; 1572 struct lock_list this, that; 1573 struct lock_list *uninitialized_var(target_entry); 1574 struct lock_list *uninitialized_var(target_entry1); 1575 1576 this.parent = NULL; 1577 1578 this.class = hlock_class(prev); 1579 ret = find_usage_backwards(&this, bit_backwards, &target_entry); 1580 if (ret < 0) 1581 return print_bfs_bug(ret); 1582 if (ret == 1) 1583 return ret; 1584 1585 that.parent = NULL; 1586 that.class = hlock_class(next); 1587 ret = find_usage_forwards(&that, bit_forwards, &target_entry1); 1588 if (ret < 0) 1589 return print_bfs_bug(ret); 1590 if (ret == 1) 1591 return ret; 1592 1593 return print_bad_irq_dependency(curr, &this, &that, 1594 target_entry, target_entry1, 1595 prev, next, 1596 bit_backwards, bit_forwards, irqclass); 1597 } 1598 1599 static const char *state_names[] = { 1600 #define LOCKDEP_STATE(__STATE) \ 1601 __stringify(__STATE), 1602 #include "lockdep_states.h" 1603 #undef LOCKDEP_STATE 1604 }; 1605 1606 static const char *state_rnames[] = { 1607 #define LOCKDEP_STATE(__STATE) \ 1608 __stringify(__STATE)"-READ", 1609 #include "lockdep_states.h" 1610 #undef LOCKDEP_STATE 1611 }; 1612 1613 static inline const char *state_name(enum lock_usage_bit bit) 1614 { 1615 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2]; 1616 } 1617 1618 static int exclusive_bit(int new_bit) 1619 { 1620 /* 1621 * USED_IN 1622 * USED_IN_READ 1623 * ENABLED 1624 * ENABLED_READ 1625 * 1626 * bit 0 - write/read 1627 * bit 1 - used_in/enabled 1628 * bit 2+ state 1629 */ 1630 1631 int state = new_bit & ~3; 1632 int dir = new_bit & 2; 1633 1634 /* 1635 * keep state, bit flip the direction and strip read. 1636 */ 1637 return state | (dir ^ 2); 1638 } 1639 1640 static int check_irq_usage(struct task_struct *curr, struct held_lock *prev, 1641 struct held_lock *next, enum lock_usage_bit bit) 1642 { 1643 /* 1644 * Prove that the new dependency does not connect a hardirq-safe 1645 * lock with a hardirq-unsafe lock - to achieve this we search 1646 * the backwards-subgraph starting at <prev>, and the 1647 * forwards-subgraph starting at <next>: 1648 */ 1649 if (!check_usage(curr, prev, next, bit, 1650 exclusive_bit(bit), state_name(bit))) 1651 return 0; 1652 1653 bit++; /* _READ */ 1654 1655 /* 1656 * Prove that the new dependency does not connect a hardirq-safe-read 1657 * lock with a hardirq-unsafe lock - to achieve this we search 1658 * the backwards-subgraph starting at <prev>, and the 1659 * forwards-subgraph starting at <next>: 1660 */ 1661 if (!check_usage(curr, prev, next, bit, 1662 exclusive_bit(bit), state_name(bit))) 1663 return 0; 1664 1665 return 1; 1666 } 1667 1668 static int 1669 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev, 1670 struct held_lock *next) 1671 { 1672 #define LOCKDEP_STATE(__STATE) \ 1673 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \ 1674 return 0; 1675 #include "lockdep_states.h" 1676 #undef LOCKDEP_STATE 1677 1678 return 1; 1679 } 1680 1681 static void inc_chains(void) 1682 { 1683 if (current->hardirq_context) 1684 nr_hardirq_chains++; 1685 else { 1686 if (current->softirq_context) 1687 nr_softirq_chains++; 1688 else 1689 nr_process_chains++; 1690 } 1691 } 1692 1693 #else 1694 1695 static inline int 1696 check_prev_add_irq(struct task_struct *curr, struct held_lock *prev, 1697 struct held_lock *next) 1698 { 1699 return 1; 1700 } 1701 1702 static inline void inc_chains(void) 1703 { 1704 nr_process_chains++; 1705 } 1706 1707 #endif 1708 1709 static void 1710 print_deadlock_scenario(struct held_lock *nxt, 1711 struct held_lock *prv) 1712 { 1713 struct lock_class *next = hlock_class(nxt); 1714 struct lock_class *prev = hlock_class(prv); 1715 1716 printk(" Possible unsafe locking scenario:\n\n"); 1717 printk(" CPU0\n"); 1718 printk(" ----\n"); 1719 printk(" lock("); 1720 __print_lock_name(prev); 1721 printk(");\n"); 1722 printk(" lock("); 1723 __print_lock_name(next); 1724 printk(");\n"); 1725 printk("\n *** DEADLOCK ***\n\n"); 1726 printk(" May be due to missing lock nesting notation\n\n"); 1727 } 1728 1729 static int 1730 print_deadlock_bug(struct task_struct *curr, struct held_lock *prev, 1731 struct held_lock *next) 1732 { 1733 if (!debug_locks_off_graph_unlock() || debug_locks_silent) 1734 return 0; 1735 1736 printk("\n"); 1737 printk("=============================================\n"); 1738 printk("[ INFO: possible recursive locking detected ]\n"); 1739 print_kernel_ident(); 1740 printk("---------------------------------------------\n"); 1741 printk("%s/%d is trying to acquire lock:\n", 1742 curr->comm, task_pid_nr(curr)); 1743 print_lock(next); 1744 printk("\nbut task is already holding lock:\n"); 1745 print_lock(prev); 1746 1747 printk("\nother info that might help us debug this:\n"); 1748 print_deadlock_scenario(next, prev); 1749 lockdep_print_held_locks(curr); 1750 1751 printk("\nstack backtrace:\n"); 1752 dump_stack(); 1753 1754 return 0; 1755 } 1756 1757 /* 1758 * Check whether we are holding such a class already. 1759 * 1760 * (Note that this has to be done separately, because the graph cannot 1761 * detect such classes of deadlocks.) 1762 * 1763 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read 1764 */ 1765 static int 1766 check_deadlock(struct task_struct *curr, struct held_lock *next, 1767 struct lockdep_map *next_instance, int read) 1768 { 1769 struct held_lock *prev; 1770 struct held_lock *nest = NULL; 1771 int i; 1772 1773 for (i = 0; i < curr->lockdep_depth; i++) { 1774 prev = curr->held_locks + i; 1775 1776 if (prev->instance == next->nest_lock) 1777 nest = prev; 1778 1779 if (hlock_class(prev) != hlock_class(next)) 1780 continue; 1781 1782 /* 1783 * Allow read-after-read recursion of the same 1784 * lock class (i.e. read_lock(lock)+read_lock(lock)): 1785 */ 1786 if ((read == 2) && prev->read) 1787 return 2; 1788 1789 /* 1790 * We're holding the nest_lock, which serializes this lock's 1791 * nesting behaviour. 1792 */ 1793 if (nest) 1794 return 2; 1795 1796 return print_deadlock_bug(curr, prev, next); 1797 } 1798 return 1; 1799 } 1800 1801 /* 1802 * There was a chain-cache miss, and we are about to add a new dependency 1803 * to a previous lock. We recursively validate the following rules: 1804 * 1805 * - would the adding of the <prev> -> <next> dependency create a 1806 * circular dependency in the graph? [== circular deadlock] 1807 * 1808 * - does the new prev->next dependency connect any hardirq-safe lock 1809 * (in the full backwards-subgraph starting at <prev>) with any 1810 * hardirq-unsafe lock (in the full forwards-subgraph starting at 1811 * <next>)? [== illegal lock inversion with hardirq contexts] 1812 * 1813 * - does the new prev->next dependency connect any softirq-safe lock 1814 * (in the full backwards-subgraph starting at <prev>) with any 1815 * softirq-unsafe lock (in the full forwards-subgraph starting at 1816 * <next>)? [== illegal lock inversion with softirq contexts] 1817 * 1818 * any of these scenarios could lead to a deadlock. 1819 * 1820 * Then if all the validations pass, we add the forwards and backwards 1821 * dependency. 1822 */ 1823 static int 1824 check_prev_add(struct task_struct *curr, struct held_lock *prev, 1825 struct held_lock *next, int distance, int trylock_loop) 1826 { 1827 struct lock_list *entry; 1828 int ret; 1829 struct lock_list this; 1830 struct lock_list *uninitialized_var(target_entry); 1831 /* 1832 * Static variable, serialized by the graph_lock(). 1833 * 1834 * We use this static variable to save the stack trace in case 1835 * we call into this function multiple times due to encountering 1836 * trylocks in the held lock stack. 1837 */ 1838 static struct stack_trace trace; 1839 1840 /* 1841 * Prove that the new <prev> -> <next> dependency would not 1842 * create a circular dependency in the graph. (We do this by 1843 * forward-recursing into the graph starting at <next>, and 1844 * checking whether we can reach <prev>.) 1845 * 1846 * We are using global variables to control the recursion, to 1847 * keep the stackframe size of the recursive functions low: 1848 */ 1849 this.class = hlock_class(next); 1850 this.parent = NULL; 1851 ret = check_noncircular(&this, hlock_class(prev), &target_entry); 1852 if (unlikely(!ret)) 1853 return print_circular_bug(&this, target_entry, next, prev); 1854 else if (unlikely(ret < 0)) 1855 return print_bfs_bug(ret); 1856 1857 if (!check_prev_add_irq(curr, prev, next)) 1858 return 0; 1859 1860 /* 1861 * For recursive read-locks we do all the dependency checks, 1862 * but we dont store read-triggered dependencies (only 1863 * write-triggered dependencies). This ensures that only the 1864 * write-side dependencies matter, and that if for example a 1865 * write-lock never takes any other locks, then the reads are 1866 * equivalent to a NOP. 1867 */ 1868 if (next->read == 2 || prev->read == 2) 1869 return 1; 1870 /* 1871 * Is the <prev> -> <next> dependency already present? 1872 * 1873 * (this may occur even though this is a new chain: consider 1874 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3 1875 * chains - the second one will be new, but L1 already has 1876 * L2 added to its dependency list, due to the first chain.) 1877 */ 1878 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) { 1879 if (entry->class == hlock_class(next)) { 1880 if (distance == 1) 1881 entry->distance = 1; 1882 return 2; 1883 } 1884 } 1885 1886 if (!trylock_loop && !save_trace(&trace)) 1887 return 0; 1888 1889 /* 1890 * Ok, all validations passed, add the new lock 1891 * to the previous lock's dependency list: 1892 */ 1893 ret = add_lock_to_list(hlock_class(prev), hlock_class(next), 1894 &hlock_class(prev)->locks_after, 1895 next->acquire_ip, distance, &trace); 1896 1897 if (!ret) 1898 return 0; 1899 1900 ret = add_lock_to_list(hlock_class(next), hlock_class(prev), 1901 &hlock_class(next)->locks_before, 1902 next->acquire_ip, distance, &trace); 1903 if (!ret) 1904 return 0; 1905 1906 /* 1907 * Debugging printouts: 1908 */ 1909 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) { 1910 graph_unlock(); 1911 printk("\n new dependency: "); 1912 print_lock_name(hlock_class(prev)); 1913 printk(" => "); 1914 print_lock_name(hlock_class(next)); 1915 printk("\n"); 1916 dump_stack(); 1917 return graph_lock(); 1918 } 1919 return 1; 1920 } 1921 1922 /* 1923 * Add the dependency to all directly-previous locks that are 'relevant'. 1924 * The ones that are relevant are (in increasing distance from curr): 1925 * all consecutive trylock entries and the final non-trylock entry - or 1926 * the end of this context's lock-chain - whichever comes first. 1927 */ 1928 static int 1929 check_prevs_add(struct task_struct *curr, struct held_lock *next) 1930 { 1931 int depth = curr->lockdep_depth; 1932 int trylock_loop = 0; 1933 struct held_lock *hlock; 1934 1935 /* 1936 * Debugging checks. 1937 * 1938 * Depth must not be zero for a non-head lock: 1939 */ 1940 if (!depth) 1941 goto out_bug; 1942 /* 1943 * At least two relevant locks must exist for this 1944 * to be a head: 1945 */ 1946 if (curr->held_locks[depth].irq_context != 1947 curr->held_locks[depth-1].irq_context) 1948 goto out_bug; 1949 1950 for (;;) { 1951 int distance = curr->lockdep_depth - depth + 1; 1952 hlock = curr->held_locks + depth - 1; 1953 /* 1954 * Only non-recursive-read entries get new dependencies 1955 * added: 1956 */ 1957 if (hlock->read != 2 && hlock->check) { 1958 if (!check_prev_add(curr, hlock, next, 1959 distance, trylock_loop)) 1960 return 0; 1961 /* 1962 * Stop after the first non-trylock entry, 1963 * as non-trylock entries have added their 1964 * own direct dependencies already, so this 1965 * lock is connected to them indirectly: 1966 */ 1967 if (!hlock->trylock) 1968 break; 1969 } 1970 depth--; 1971 /* 1972 * End of lock-stack? 1973 */ 1974 if (!depth) 1975 break; 1976 /* 1977 * Stop the search if we cross into another context: 1978 */ 1979 if (curr->held_locks[depth].irq_context != 1980 curr->held_locks[depth-1].irq_context) 1981 break; 1982 trylock_loop = 1; 1983 } 1984 return 1; 1985 out_bug: 1986 if (!debug_locks_off_graph_unlock()) 1987 return 0; 1988 1989 /* 1990 * Clearly we all shouldn't be here, but since we made it we 1991 * can reliable say we messed up our state. See the above two 1992 * gotos for reasons why we could possibly end up here. 1993 */ 1994 WARN_ON(1); 1995 1996 return 0; 1997 } 1998 1999 unsigned long nr_lock_chains; 2000 struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS]; 2001 int nr_chain_hlocks; 2002 static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS]; 2003 2004 struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i) 2005 { 2006 return lock_classes + chain_hlocks[chain->base + i]; 2007 } 2008 2009 /* 2010 * Look up a dependency chain. If the key is not present yet then 2011 * add it and return 1 - in this case the new dependency chain is 2012 * validated. If the key is already hashed, return 0. 2013 * (On return with 1 graph_lock is held.) 2014 */ 2015 static inline int lookup_chain_cache(struct task_struct *curr, 2016 struct held_lock *hlock, 2017 u64 chain_key) 2018 { 2019 struct lock_class *class = hlock_class(hlock); 2020 struct list_head *hash_head = chainhashentry(chain_key); 2021 struct lock_chain *chain; 2022 struct held_lock *hlock_curr; 2023 int i, j; 2024 2025 /* 2026 * We might need to take the graph lock, ensure we've got IRQs 2027 * disabled to make this an IRQ-safe lock.. for recursion reasons 2028 * lockdep won't complain about its own locking errors. 2029 */ 2030 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) 2031 return 0; 2032 /* 2033 * We can walk it lock-free, because entries only get added 2034 * to the hash: 2035 */ 2036 list_for_each_entry_rcu(chain, hash_head, entry) { 2037 if (chain->chain_key == chain_key) { 2038 cache_hit: 2039 debug_atomic_inc(chain_lookup_hits); 2040 if (very_verbose(class)) 2041 printk("\nhash chain already cached, key: " 2042 "%016Lx tail class: [%p] %s\n", 2043 (unsigned long long)chain_key, 2044 class->key, class->name); 2045 return 0; 2046 } 2047 } 2048 if (very_verbose(class)) 2049 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n", 2050 (unsigned long long)chain_key, class->key, class->name); 2051 /* 2052 * Allocate a new chain entry from the static array, and add 2053 * it to the hash: 2054 */ 2055 if (!graph_lock()) 2056 return 0; 2057 /* 2058 * We have to walk the chain again locked - to avoid duplicates: 2059 */ 2060 list_for_each_entry(chain, hash_head, entry) { 2061 if (chain->chain_key == chain_key) { 2062 graph_unlock(); 2063 goto cache_hit; 2064 } 2065 } 2066 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) { 2067 if (!debug_locks_off_graph_unlock()) 2068 return 0; 2069 2070 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!"); 2071 dump_stack(); 2072 return 0; 2073 } 2074 chain = lock_chains + nr_lock_chains++; 2075 chain->chain_key = chain_key; 2076 chain->irq_context = hlock->irq_context; 2077 /* Find the first held_lock of current chain */ 2078 for (i = curr->lockdep_depth - 1; i >= 0; i--) { 2079 hlock_curr = curr->held_locks + i; 2080 if (hlock_curr->irq_context != hlock->irq_context) 2081 break; 2082 } 2083 i++; 2084 chain->depth = curr->lockdep_depth + 1 - i; 2085 if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) { 2086 chain->base = nr_chain_hlocks; 2087 nr_chain_hlocks += chain->depth; 2088 for (j = 0; j < chain->depth - 1; j++, i++) { 2089 int lock_id = curr->held_locks[i].class_idx - 1; 2090 chain_hlocks[chain->base + j] = lock_id; 2091 } 2092 chain_hlocks[chain->base + j] = class - lock_classes; 2093 } 2094 list_add_tail_rcu(&chain->entry, hash_head); 2095 debug_atomic_inc(chain_lookup_misses); 2096 inc_chains(); 2097 2098 return 1; 2099 } 2100 2101 static int validate_chain(struct task_struct *curr, struct lockdep_map *lock, 2102 struct held_lock *hlock, int chain_head, u64 chain_key) 2103 { 2104 /* 2105 * Trylock needs to maintain the stack of held locks, but it 2106 * does not add new dependencies, because trylock can be done 2107 * in any order. 2108 * 2109 * We look up the chain_key and do the O(N^2) check and update of 2110 * the dependencies only if this is a new dependency chain. 2111 * (If lookup_chain_cache() returns with 1 it acquires 2112 * graph_lock for us) 2113 */ 2114 if (!hlock->trylock && hlock->check && 2115 lookup_chain_cache(curr, hlock, chain_key)) { 2116 /* 2117 * Check whether last held lock: 2118 * 2119 * - is irq-safe, if this lock is irq-unsafe 2120 * - is softirq-safe, if this lock is hardirq-unsafe 2121 * 2122 * And check whether the new lock's dependency graph 2123 * could lead back to the previous lock. 2124 * 2125 * any of these scenarios could lead to a deadlock. If 2126 * All validations 2127 */ 2128 int ret = check_deadlock(curr, hlock, lock, hlock->read); 2129 2130 if (!ret) 2131 return 0; 2132 /* 2133 * Mark recursive read, as we jump over it when 2134 * building dependencies (just like we jump over 2135 * trylock entries): 2136 */ 2137 if (ret == 2) 2138 hlock->read = 2; 2139 /* 2140 * Add dependency only if this lock is not the head 2141 * of the chain, and if it's not a secondary read-lock: 2142 */ 2143 if (!chain_head && ret != 2) 2144 if (!check_prevs_add(curr, hlock)) 2145 return 0; 2146 graph_unlock(); 2147 } else 2148 /* after lookup_chain_cache(): */ 2149 if (unlikely(!debug_locks)) 2150 return 0; 2151 2152 return 1; 2153 } 2154 #else 2155 static inline int validate_chain(struct task_struct *curr, 2156 struct lockdep_map *lock, struct held_lock *hlock, 2157 int chain_head, u64 chain_key) 2158 { 2159 return 1; 2160 } 2161 #endif 2162 2163 /* 2164 * We are building curr_chain_key incrementally, so double-check 2165 * it from scratch, to make sure that it's done correctly: 2166 */ 2167 static void check_chain_key(struct task_struct *curr) 2168 { 2169 #ifdef CONFIG_DEBUG_LOCKDEP 2170 struct held_lock *hlock, *prev_hlock = NULL; 2171 unsigned int i, id; 2172 u64 chain_key = 0; 2173 2174 for (i = 0; i < curr->lockdep_depth; i++) { 2175 hlock = curr->held_locks + i; 2176 if (chain_key != hlock->prev_chain_key) { 2177 debug_locks_off(); 2178 /* 2179 * We got mighty confused, our chain keys don't match 2180 * with what we expect, someone trample on our task state? 2181 */ 2182 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n", 2183 curr->lockdep_depth, i, 2184 (unsigned long long)chain_key, 2185 (unsigned long long)hlock->prev_chain_key); 2186 return; 2187 } 2188 id = hlock->class_idx - 1; 2189 /* 2190 * Whoops ran out of static storage again? 2191 */ 2192 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS)) 2193 return; 2194 2195 if (prev_hlock && (prev_hlock->irq_context != 2196 hlock->irq_context)) 2197 chain_key = 0; 2198 chain_key = iterate_chain_key(chain_key, id); 2199 prev_hlock = hlock; 2200 } 2201 if (chain_key != curr->curr_chain_key) { 2202 debug_locks_off(); 2203 /* 2204 * More smoking hash instead of calculating it, damn see these 2205 * numbers float.. I bet that a pink elephant stepped on my memory. 2206 */ 2207 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n", 2208 curr->lockdep_depth, i, 2209 (unsigned long long)chain_key, 2210 (unsigned long long)curr->curr_chain_key); 2211 } 2212 #endif 2213 } 2214 2215 static void 2216 print_usage_bug_scenario(struct held_lock *lock) 2217 { 2218 struct lock_class *class = hlock_class(lock); 2219 2220 printk(" Possible unsafe locking scenario:\n\n"); 2221 printk(" CPU0\n"); 2222 printk(" ----\n"); 2223 printk(" lock("); 2224 __print_lock_name(class); 2225 printk(");\n"); 2226 printk(" <Interrupt>\n"); 2227 printk(" lock("); 2228 __print_lock_name(class); 2229 printk(");\n"); 2230 printk("\n *** DEADLOCK ***\n\n"); 2231 } 2232 2233 static int 2234 print_usage_bug(struct task_struct *curr, struct held_lock *this, 2235 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit) 2236 { 2237 if (!debug_locks_off_graph_unlock() || debug_locks_silent) 2238 return 0; 2239 2240 printk("\n"); 2241 printk("=================================\n"); 2242 printk("[ INFO: inconsistent lock state ]\n"); 2243 print_kernel_ident(); 2244 printk("---------------------------------\n"); 2245 2246 printk("inconsistent {%s} -> {%s} usage.\n", 2247 usage_str[prev_bit], usage_str[new_bit]); 2248 2249 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n", 2250 curr->comm, task_pid_nr(curr), 2251 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT, 2252 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT, 2253 trace_hardirqs_enabled(curr), 2254 trace_softirqs_enabled(curr)); 2255 print_lock(this); 2256 2257 printk("{%s} state was registered at:\n", usage_str[prev_bit]); 2258 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1); 2259 2260 print_irqtrace_events(curr); 2261 printk("\nother info that might help us debug this:\n"); 2262 print_usage_bug_scenario(this); 2263 2264 lockdep_print_held_locks(curr); 2265 2266 printk("\nstack backtrace:\n"); 2267 dump_stack(); 2268 2269 return 0; 2270 } 2271 2272 /* 2273 * Print out an error if an invalid bit is set: 2274 */ 2275 static inline int 2276 valid_state(struct task_struct *curr, struct held_lock *this, 2277 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit) 2278 { 2279 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) 2280 return print_usage_bug(curr, this, bad_bit, new_bit); 2281 return 1; 2282 } 2283 2284 static int mark_lock(struct task_struct *curr, struct held_lock *this, 2285 enum lock_usage_bit new_bit); 2286 2287 #if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) 2288 2289 /* 2290 * print irq inversion bug: 2291 */ 2292 static int 2293 print_irq_inversion_bug(struct task_struct *curr, 2294 struct lock_list *root, struct lock_list *other, 2295 struct held_lock *this, int forwards, 2296 const char *irqclass) 2297 { 2298 struct lock_list *entry = other; 2299 struct lock_list *middle = NULL; 2300 int depth; 2301 2302 if (!debug_locks_off_graph_unlock() || debug_locks_silent) 2303 return 0; 2304 2305 printk("\n"); 2306 printk("=========================================================\n"); 2307 printk("[ INFO: possible irq lock inversion dependency detected ]\n"); 2308 print_kernel_ident(); 2309 printk("---------------------------------------------------------\n"); 2310 printk("%s/%d just changed the state of lock:\n", 2311 curr->comm, task_pid_nr(curr)); 2312 print_lock(this); 2313 if (forwards) 2314 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass); 2315 else 2316 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass); 2317 print_lock_name(other->class); 2318 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n"); 2319 2320 printk("\nother info that might help us debug this:\n"); 2321 2322 /* Find a middle lock (if one exists) */ 2323 depth = get_lock_depth(other); 2324 do { 2325 if (depth == 0 && (entry != root)) { 2326 printk("lockdep:%s bad path found in chain graph\n", __func__); 2327 break; 2328 } 2329 middle = entry; 2330 entry = get_lock_parent(entry); 2331 depth--; 2332 } while (entry && entry != root && (depth >= 0)); 2333 if (forwards) 2334 print_irq_lock_scenario(root, other, 2335 middle ? middle->class : root->class, other->class); 2336 else 2337 print_irq_lock_scenario(other, root, 2338 middle ? middle->class : other->class, root->class); 2339 2340 lockdep_print_held_locks(curr); 2341 2342 printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n"); 2343 if (!save_trace(&root->trace)) 2344 return 0; 2345 print_shortest_lock_dependencies(other, root); 2346 2347 printk("\nstack backtrace:\n"); 2348 dump_stack(); 2349 2350 return 0; 2351 } 2352 2353 /* 2354 * Prove that in the forwards-direction subgraph starting at <this> 2355 * there is no lock matching <mask>: 2356 */ 2357 static int 2358 check_usage_forwards(struct task_struct *curr, struct held_lock *this, 2359 enum lock_usage_bit bit, const char *irqclass) 2360 { 2361 int ret; 2362 struct lock_list root; 2363 struct lock_list *uninitialized_var(target_entry); 2364 2365 root.parent = NULL; 2366 root.class = hlock_class(this); 2367 ret = find_usage_forwards(&root, bit, &target_entry); 2368 if (ret < 0) 2369 return print_bfs_bug(ret); 2370 if (ret == 1) 2371 return ret; 2372 2373 return print_irq_inversion_bug(curr, &root, target_entry, 2374 this, 1, irqclass); 2375 } 2376 2377 /* 2378 * Prove that in the backwards-direction subgraph starting at <this> 2379 * there is no lock matching <mask>: 2380 */ 2381 static int 2382 check_usage_backwards(struct task_struct *curr, struct held_lock *this, 2383 enum lock_usage_bit bit, const char *irqclass) 2384 { 2385 int ret; 2386 struct lock_list root; 2387 struct lock_list *uninitialized_var(target_entry); 2388 2389 root.parent = NULL; 2390 root.class = hlock_class(this); 2391 ret = find_usage_backwards(&root, bit, &target_entry); 2392 if (ret < 0) 2393 return print_bfs_bug(ret); 2394 if (ret == 1) 2395 return ret; 2396 2397 return print_irq_inversion_bug(curr, &root, target_entry, 2398 this, 0, irqclass); 2399 } 2400 2401 void print_irqtrace_events(struct task_struct *curr) 2402 { 2403 printk("irq event stamp: %u\n", curr->irq_events); 2404 printk("hardirqs last enabled at (%u): ", curr->hardirq_enable_event); 2405 print_ip_sym(curr->hardirq_enable_ip); 2406 printk("hardirqs last disabled at (%u): ", curr->hardirq_disable_event); 2407 print_ip_sym(curr->hardirq_disable_ip); 2408 printk("softirqs last enabled at (%u): ", curr->softirq_enable_event); 2409 print_ip_sym(curr->softirq_enable_ip); 2410 printk("softirqs last disabled at (%u): ", curr->softirq_disable_event); 2411 print_ip_sym(curr->softirq_disable_ip); 2412 } 2413 2414 static int HARDIRQ_verbose(struct lock_class *class) 2415 { 2416 #if HARDIRQ_VERBOSE 2417 return class_filter(class); 2418 #endif 2419 return 0; 2420 } 2421 2422 static int SOFTIRQ_verbose(struct lock_class *class) 2423 { 2424 #if SOFTIRQ_VERBOSE 2425 return class_filter(class); 2426 #endif 2427 return 0; 2428 } 2429 2430 static int RECLAIM_FS_verbose(struct lock_class *class) 2431 { 2432 #if RECLAIM_VERBOSE 2433 return class_filter(class); 2434 #endif 2435 return 0; 2436 } 2437 2438 #define STRICT_READ_CHECKS 1 2439 2440 static int (*state_verbose_f[])(struct lock_class *class) = { 2441 #define LOCKDEP_STATE(__STATE) \ 2442 __STATE##_verbose, 2443 #include "lockdep_states.h" 2444 #undef LOCKDEP_STATE 2445 }; 2446 2447 static inline int state_verbose(enum lock_usage_bit bit, 2448 struct lock_class *class) 2449 { 2450 return state_verbose_f[bit >> 2](class); 2451 } 2452 2453 typedef int (*check_usage_f)(struct task_struct *, struct held_lock *, 2454 enum lock_usage_bit bit, const char *name); 2455 2456 static int 2457 mark_lock_irq(struct task_struct *curr, struct held_lock *this, 2458 enum lock_usage_bit new_bit) 2459 { 2460 int excl_bit = exclusive_bit(new_bit); 2461 int read = new_bit & 1; 2462 int dir = new_bit & 2; 2463 2464 /* 2465 * mark USED_IN has to look forwards -- to ensure no dependency 2466 * has ENABLED state, which would allow recursion deadlocks. 2467 * 2468 * mark ENABLED has to look backwards -- to ensure no dependee 2469 * has USED_IN state, which, again, would allow recursion deadlocks. 2470 */ 2471 check_usage_f usage = dir ? 2472 check_usage_backwards : check_usage_forwards; 2473 2474 /* 2475 * Validate that this particular lock does not have conflicting 2476 * usage states. 2477 */ 2478 if (!valid_state(curr, this, new_bit, excl_bit)) 2479 return 0; 2480 2481 /* 2482 * Validate that the lock dependencies don't have conflicting usage 2483 * states. 2484 */ 2485 if ((!read || !dir || STRICT_READ_CHECKS) && 2486 !usage(curr, this, excl_bit, state_name(new_bit & ~1))) 2487 return 0; 2488 2489 /* 2490 * Check for read in write conflicts 2491 */ 2492 if (!read) { 2493 if (!valid_state(curr, this, new_bit, excl_bit + 1)) 2494 return 0; 2495 2496 if (STRICT_READ_CHECKS && 2497 !usage(curr, this, excl_bit + 1, 2498 state_name(new_bit + 1))) 2499 return 0; 2500 } 2501 2502 if (state_verbose(new_bit, hlock_class(this))) 2503 return 2; 2504 2505 return 1; 2506 } 2507 2508 enum mark_type { 2509 #define LOCKDEP_STATE(__STATE) __STATE, 2510 #include "lockdep_states.h" 2511 #undef LOCKDEP_STATE 2512 }; 2513 2514 /* 2515 * Mark all held locks with a usage bit: 2516 */ 2517 static int 2518 mark_held_locks(struct task_struct *curr, enum mark_type mark) 2519 { 2520 enum lock_usage_bit usage_bit; 2521 struct held_lock *hlock; 2522 int i; 2523 2524 for (i = 0; i < curr->lockdep_depth; i++) { 2525 hlock = curr->held_locks + i; 2526 2527 usage_bit = 2 + (mark << 2); /* ENABLED */ 2528 if (hlock->read) 2529 usage_bit += 1; /* READ */ 2530 2531 BUG_ON(usage_bit >= LOCK_USAGE_STATES); 2532 2533 if (!hlock->check) 2534 continue; 2535 2536 if (!mark_lock(curr, hlock, usage_bit)) 2537 return 0; 2538 } 2539 2540 return 1; 2541 } 2542 2543 /* 2544 * Hardirqs will be enabled: 2545 */ 2546 static void __trace_hardirqs_on_caller(unsigned long ip) 2547 { 2548 struct task_struct *curr = current; 2549 2550 /* we'll do an OFF -> ON transition: */ 2551 curr->hardirqs_enabled = 1; 2552 2553 /* 2554 * We are going to turn hardirqs on, so set the 2555 * usage bit for all held locks: 2556 */ 2557 if (!mark_held_locks(curr, HARDIRQ)) 2558 return; 2559 /* 2560 * If we have softirqs enabled, then set the usage 2561 * bit for all held locks. (disabled hardirqs prevented 2562 * this bit from being set before) 2563 */ 2564 if (curr->softirqs_enabled) 2565 if (!mark_held_locks(curr, SOFTIRQ)) 2566 return; 2567 2568 curr->hardirq_enable_ip = ip; 2569 curr->hardirq_enable_event = ++curr->irq_events; 2570 debug_atomic_inc(hardirqs_on_events); 2571 } 2572 2573 __visible void trace_hardirqs_on_caller(unsigned long ip) 2574 { 2575 time_hardirqs_on(CALLER_ADDR0, ip); 2576 2577 if (unlikely(!debug_locks || current->lockdep_recursion)) 2578 return; 2579 2580 if (unlikely(current->hardirqs_enabled)) { 2581 /* 2582 * Neither irq nor preemption are disabled here 2583 * so this is racy by nature but losing one hit 2584 * in a stat is not a big deal. 2585 */ 2586 __debug_atomic_inc(redundant_hardirqs_on); 2587 return; 2588 } 2589 2590 /* 2591 * We're enabling irqs and according to our state above irqs weren't 2592 * already enabled, yet we find the hardware thinks they are in fact 2593 * enabled.. someone messed up their IRQ state tracing. 2594 */ 2595 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) 2596 return; 2597 2598 /* 2599 * See the fine text that goes along with this variable definition. 2600 */ 2601 if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled))) 2602 return; 2603 2604 /* 2605 * Can't allow enabling interrupts while in an interrupt handler, 2606 * that's general bad form and such. Recursion, limited stack etc.. 2607 */ 2608 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context)) 2609 return; 2610 2611 current->lockdep_recursion = 1; 2612 __trace_hardirqs_on_caller(ip); 2613 current->lockdep_recursion = 0; 2614 } 2615 EXPORT_SYMBOL(trace_hardirqs_on_caller); 2616 2617 void trace_hardirqs_on(void) 2618 { 2619 trace_hardirqs_on_caller(CALLER_ADDR0); 2620 } 2621 EXPORT_SYMBOL(trace_hardirqs_on); 2622 2623 /* 2624 * Hardirqs were disabled: 2625 */ 2626 __visible void trace_hardirqs_off_caller(unsigned long ip) 2627 { 2628 struct task_struct *curr = current; 2629 2630 time_hardirqs_off(CALLER_ADDR0, ip); 2631 2632 if (unlikely(!debug_locks || current->lockdep_recursion)) 2633 return; 2634 2635 /* 2636 * So we're supposed to get called after you mask local IRQs, but for 2637 * some reason the hardware doesn't quite think you did a proper job. 2638 */ 2639 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) 2640 return; 2641 2642 if (curr->hardirqs_enabled) { 2643 /* 2644 * We have done an ON -> OFF transition: 2645 */ 2646 curr->hardirqs_enabled = 0; 2647 curr->hardirq_disable_ip = ip; 2648 curr->hardirq_disable_event = ++curr->irq_events; 2649 debug_atomic_inc(hardirqs_off_events); 2650 } else 2651 debug_atomic_inc(redundant_hardirqs_off); 2652 } 2653 EXPORT_SYMBOL(trace_hardirqs_off_caller); 2654 2655 void trace_hardirqs_off(void) 2656 { 2657 trace_hardirqs_off_caller(CALLER_ADDR0); 2658 } 2659 EXPORT_SYMBOL(trace_hardirqs_off); 2660 2661 /* 2662 * Softirqs will be enabled: 2663 */ 2664 void trace_softirqs_on(unsigned long ip) 2665 { 2666 struct task_struct *curr = current; 2667 2668 if (unlikely(!debug_locks || current->lockdep_recursion)) 2669 return; 2670 2671 /* 2672 * We fancy IRQs being disabled here, see softirq.c, avoids 2673 * funny state and nesting things. 2674 */ 2675 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) 2676 return; 2677 2678 if (curr->softirqs_enabled) { 2679 debug_atomic_inc(redundant_softirqs_on); 2680 return; 2681 } 2682 2683 current->lockdep_recursion = 1; 2684 /* 2685 * We'll do an OFF -> ON transition: 2686 */ 2687 curr->softirqs_enabled = 1; 2688 curr->softirq_enable_ip = ip; 2689 curr->softirq_enable_event = ++curr->irq_events; 2690 debug_atomic_inc(softirqs_on_events); 2691 /* 2692 * We are going to turn softirqs on, so set the 2693 * usage bit for all held locks, if hardirqs are 2694 * enabled too: 2695 */ 2696 if (curr->hardirqs_enabled) 2697 mark_held_locks(curr, SOFTIRQ); 2698 current->lockdep_recursion = 0; 2699 } 2700 2701 /* 2702 * Softirqs were disabled: 2703 */ 2704 void trace_softirqs_off(unsigned long ip) 2705 { 2706 struct task_struct *curr = current; 2707 2708 if (unlikely(!debug_locks || current->lockdep_recursion)) 2709 return; 2710 2711 /* 2712 * We fancy IRQs being disabled here, see softirq.c 2713 */ 2714 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) 2715 return; 2716 2717 if (curr->softirqs_enabled) { 2718 /* 2719 * We have done an ON -> OFF transition: 2720 */ 2721 curr->softirqs_enabled = 0; 2722 curr->softirq_disable_ip = ip; 2723 curr->softirq_disable_event = ++curr->irq_events; 2724 debug_atomic_inc(softirqs_off_events); 2725 /* 2726 * Whoops, we wanted softirqs off, so why aren't they? 2727 */ 2728 DEBUG_LOCKS_WARN_ON(!softirq_count()); 2729 } else 2730 debug_atomic_inc(redundant_softirqs_off); 2731 } 2732 2733 static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags) 2734 { 2735 struct task_struct *curr = current; 2736 2737 if (unlikely(!debug_locks)) 2738 return; 2739 2740 /* no reclaim without waiting on it */ 2741 if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) 2742 return; 2743 2744 /* this guy won't enter reclaim */ 2745 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC)) 2746 return; 2747 2748 /* We're only interested __GFP_FS allocations for now */ 2749 if (!(gfp_mask & __GFP_FS)) 2750 return; 2751 2752 /* 2753 * Oi! Can't be having __GFP_FS allocations with IRQs disabled. 2754 */ 2755 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))) 2756 return; 2757 2758 mark_held_locks(curr, RECLAIM_FS); 2759 } 2760 2761 static void check_flags(unsigned long flags); 2762 2763 void lockdep_trace_alloc(gfp_t gfp_mask) 2764 { 2765 unsigned long flags; 2766 2767 if (unlikely(current->lockdep_recursion)) 2768 return; 2769 2770 raw_local_irq_save(flags); 2771 check_flags(flags); 2772 current->lockdep_recursion = 1; 2773 __lockdep_trace_alloc(gfp_mask, flags); 2774 current->lockdep_recursion = 0; 2775 raw_local_irq_restore(flags); 2776 } 2777 2778 static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock) 2779 { 2780 /* 2781 * If non-trylock use in a hardirq or softirq context, then 2782 * mark the lock as used in these contexts: 2783 */ 2784 if (!hlock->trylock) { 2785 if (hlock->read) { 2786 if (curr->hardirq_context) 2787 if (!mark_lock(curr, hlock, 2788 LOCK_USED_IN_HARDIRQ_READ)) 2789 return 0; 2790 if (curr->softirq_context) 2791 if (!mark_lock(curr, hlock, 2792 LOCK_USED_IN_SOFTIRQ_READ)) 2793 return 0; 2794 } else { 2795 if (curr->hardirq_context) 2796 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ)) 2797 return 0; 2798 if (curr->softirq_context) 2799 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ)) 2800 return 0; 2801 } 2802 } 2803 if (!hlock->hardirqs_off) { 2804 if (hlock->read) { 2805 if (!mark_lock(curr, hlock, 2806 LOCK_ENABLED_HARDIRQ_READ)) 2807 return 0; 2808 if (curr->softirqs_enabled) 2809 if (!mark_lock(curr, hlock, 2810 LOCK_ENABLED_SOFTIRQ_READ)) 2811 return 0; 2812 } else { 2813 if (!mark_lock(curr, hlock, 2814 LOCK_ENABLED_HARDIRQ)) 2815 return 0; 2816 if (curr->softirqs_enabled) 2817 if (!mark_lock(curr, hlock, 2818 LOCK_ENABLED_SOFTIRQ)) 2819 return 0; 2820 } 2821 } 2822 2823 /* 2824 * We reuse the irq context infrastructure more broadly as a general 2825 * context checking code. This tests GFP_FS recursion (a lock taken 2826 * during reclaim for a GFP_FS allocation is held over a GFP_FS 2827 * allocation). 2828 */ 2829 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) { 2830 if (hlock->read) { 2831 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ)) 2832 return 0; 2833 } else { 2834 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS)) 2835 return 0; 2836 } 2837 } 2838 2839 return 1; 2840 } 2841 2842 static int separate_irq_context(struct task_struct *curr, 2843 struct held_lock *hlock) 2844 { 2845 unsigned int depth = curr->lockdep_depth; 2846 2847 /* 2848 * Keep track of points where we cross into an interrupt context: 2849 */ 2850 hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) + 2851 curr->softirq_context; 2852 if (depth) { 2853 struct held_lock *prev_hlock; 2854 2855 prev_hlock = curr->held_locks + depth-1; 2856 /* 2857 * If we cross into another context, reset the 2858 * hash key (this also prevents the checking and the 2859 * adding of the dependency to 'prev'): 2860 */ 2861 if (prev_hlock->irq_context != hlock->irq_context) 2862 return 1; 2863 } 2864 return 0; 2865 } 2866 2867 #else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */ 2868 2869 static inline 2870 int mark_lock_irq(struct task_struct *curr, struct held_lock *this, 2871 enum lock_usage_bit new_bit) 2872 { 2873 WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */ 2874 return 1; 2875 } 2876 2877 static inline int mark_irqflags(struct task_struct *curr, 2878 struct held_lock *hlock) 2879 { 2880 return 1; 2881 } 2882 2883 static inline int separate_irq_context(struct task_struct *curr, 2884 struct held_lock *hlock) 2885 { 2886 return 0; 2887 } 2888 2889 void lockdep_trace_alloc(gfp_t gfp_mask) 2890 { 2891 } 2892 2893 #endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */ 2894 2895 /* 2896 * Mark a lock with a usage bit, and validate the state transition: 2897 */ 2898 static int mark_lock(struct task_struct *curr, struct held_lock *this, 2899 enum lock_usage_bit new_bit) 2900 { 2901 unsigned int new_mask = 1 << new_bit, ret = 1; 2902 2903 /* 2904 * If already set then do not dirty the cacheline, 2905 * nor do any checks: 2906 */ 2907 if (likely(hlock_class(this)->usage_mask & new_mask)) 2908 return 1; 2909 2910 if (!graph_lock()) 2911 return 0; 2912 /* 2913 * Make sure we didn't race: 2914 */ 2915 if (unlikely(hlock_class(this)->usage_mask & new_mask)) { 2916 graph_unlock(); 2917 return 1; 2918 } 2919 2920 hlock_class(this)->usage_mask |= new_mask; 2921 2922 if (!save_trace(hlock_class(this)->usage_traces + new_bit)) 2923 return 0; 2924 2925 switch (new_bit) { 2926 #define LOCKDEP_STATE(__STATE) \ 2927 case LOCK_USED_IN_##__STATE: \ 2928 case LOCK_USED_IN_##__STATE##_READ: \ 2929 case LOCK_ENABLED_##__STATE: \ 2930 case LOCK_ENABLED_##__STATE##_READ: 2931 #include "lockdep_states.h" 2932 #undef LOCKDEP_STATE 2933 ret = mark_lock_irq(curr, this, new_bit); 2934 if (!ret) 2935 return 0; 2936 break; 2937 case LOCK_USED: 2938 debug_atomic_dec(nr_unused_locks); 2939 break; 2940 default: 2941 if (!debug_locks_off_graph_unlock()) 2942 return 0; 2943 WARN_ON(1); 2944 return 0; 2945 } 2946 2947 graph_unlock(); 2948 2949 /* 2950 * We must printk outside of the graph_lock: 2951 */ 2952 if (ret == 2) { 2953 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]); 2954 print_lock(this); 2955 print_irqtrace_events(curr); 2956 dump_stack(); 2957 } 2958 2959 return ret; 2960 } 2961 2962 /* 2963 * Initialize a lock instance's lock-class mapping info: 2964 */ 2965 void lockdep_init_map(struct lockdep_map *lock, const char *name, 2966 struct lock_class_key *key, int subclass) 2967 { 2968 int i; 2969 2970 kmemcheck_mark_initialized(lock, sizeof(*lock)); 2971 2972 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++) 2973 lock->class_cache[i] = NULL; 2974 2975 #ifdef CONFIG_LOCK_STAT 2976 lock->cpu = raw_smp_processor_id(); 2977 #endif 2978 2979 /* 2980 * Can't be having no nameless bastards around this place! 2981 */ 2982 if (DEBUG_LOCKS_WARN_ON(!name)) { 2983 lock->name = "NULL"; 2984 return; 2985 } 2986 2987 lock->name = name; 2988 2989 /* 2990 * No key, no joy, we need to hash something. 2991 */ 2992 if (DEBUG_LOCKS_WARN_ON(!key)) 2993 return; 2994 /* 2995 * Sanity check, the lock-class key must be persistent: 2996 */ 2997 if (!static_obj(key)) { 2998 printk("BUG: key %p not in .data!\n", key); 2999 /* 3000 * What it says above ^^^^^, I suggest you read it. 3001 */ 3002 DEBUG_LOCKS_WARN_ON(1); 3003 return; 3004 } 3005 lock->key = key; 3006 3007 if (unlikely(!debug_locks)) 3008 return; 3009 3010 if (subclass) { 3011 unsigned long flags; 3012 3013 if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion)) 3014 return; 3015 3016 raw_local_irq_save(flags); 3017 current->lockdep_recursion = 1; 3018 register_lock_class(lock, subclass, 1); 3019 current->lockdep_recursion = 0; 3020 raw_local_irq_restore(flags); 3021 } 3022 } 3023 EXPORT_SYMBOL_GPL(lockdep_init_map); 3024 3025 struct lock_class_key __lockdep_no_validate__; 3026 EXPORT_SYMBOL_GPL(__lockdep_no_validate__); 3027 3028 static int 3029 print_lock_nested_lock_not_held(struct task_struct *curr, 3030 struct held_lock *hlock, 3031 unsigned long ip) 3032 { 3033 if (!debug_locks_off()) 3034 return 0; 3035 if (debug_locks_silent) 3036 return 0; 3037 3038 printk("\n"); 3039 printk("==================================\n"); 3040 printk("[ BUG: Nested lock was not taken ]\n"); 3041 print_kernel_ident(); 3042 printk("----------------------------------\n"); 3043 3044 printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr)); 3045 print_lock(hlock); 3046 3047 printk("\nbut this task is not holding:\n"); 3048 printk("%s\n", hlock->nest_lock->name); 3049 3050 printk("\nstack backtrace:\n"); 3051 dump_stack(); 3052 3053 printk("\nother info that might help us debug this:\n"); 3054 lockdep_print_held_locks(curr); 3055 3056 printk("\nstack backtrace:\n"); 3057 dump_stack(); 3058 3059 return 0; 3060 } 3061 3062 static int __lock_is_held(struct lockdep_map *lock); 3063 3064 /* 3065 * This gets called for every mutex_lock*()/spin_lock*() operation. 3066 * We maintain the dependency maps and validate the locking attempt: 3067 */ 3068 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass, 3069 int trylock, int read, int check, int hardirqs_off, 3070 struct lockdep_map *nest_lock, unsigned long ip, 3071 int references, int pin_count) 3072 { 3073 struct task_struct *curr = current; 3074 struct lock_class *class = NULL; 3075 struct held_lock *hlock; 3076 unsigned int depth, id; 3077 int chain_head = 0; 3078 int class_idx; 3079 u64 chain_key; 3080 3081 if (unlikely(!debug_locks)) 3082 return 0; 3083 3084 /* 3085 * Lockdep should run with IRQs disabled, otherwise we could 3086 * get an interrupt which would want to take locks, which would 3087 * end up in lockdep and have you got a head-ache already? 3088 */ 3089 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled())) 3090 return 0; 3091 3092 if (!prove_locking || lock->key == &__lockdep_no_validate__) 3093 check = 0; 3094 3095 if (subclass < NR_LOCKDEP_CACHING_CLASSES) 3096 class = lock->class_cache[subclass]; 3097 /* 3098 * Not cached? 3099 */ 3100 if (unlikely(!class)) { 3101 class = register_lock_class(lock, subclass, 0); 3102 if (!class) 3103 return 0; 3104 } 3105 atomic_inc((atomic_t *)&class->ops); 3106 if (very_verbose(class)) { 3107 printk("\nacquire class [%p] %s", class->key, class->name); 3108 if (class->name_version > 1) 3109 printk("#%d", class->name_version); 3110 printk("\n"); 3111 dump_stack(); 3112 } 3113 3114 /* 3115 * Add the lock to the list of currently held locks. 3116 * (we dont increase the depth just yet, up until the 3117 * dependency checks are done) 3118 */ 3119 depth = curr->lockdep_depth; 3120 /* 3121 * Ran out of static storage for our per-task lock stack again have we? 3122 */ 3123 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH)) 3124 return 0; 3125 3126 class_idx = class - lock_classes + 1; 3127 3128 if (depth) { 3129 hlock = curr->held_locks + depth - 1; 3130 if (hlock->class_idx == class_idx && nest_lock) { 3131 if (hlock->references) 3132 hlock->references++; 3133 else 3134 hlock->references = 2; 3135 3136 return 1; 3137 } 3138 } 3139 3140 hlock = curr->held_locks + depth; 3141 /* 3142 * Plain impossible, we just registered it and checked it weren't no 3143 * NULL like.. I bet this mushroom I ate was good! 3144 */ 3145 if (DEBUG_LOCKS_WARN_ON(!class)) 3146 return 0; 3147 hlock->class_idx = class_idx; 3148 hlock->acquire_ip = ip; 3149 hlock->instance = lock; 3150 hlock->nest_lock = nest_lock; 3151 hlock->trylock = trylock; 3152 hlock->read = read; 3153 hlock->check = check; 3154 hlock->hardirqs_off = !!hardirqs_off; 3155 hlock->references = references; 3156 #ifdef CONFIG_LOCK_STAT 3157 hlock->waittime_stamp = 0; 3158 hlock->holdtime_stamp = lockstat_clock(); 3159 #endif 3160 hlock->pin_count = pin_count; 3161 3162 if (check && !mark_irqflags(curr, hlock)) 3163 return 0; 3164 3165 /* mark it as used: */ 3166 if (!mark_lock(curr, hlock, LOCK_USED)) 3167 return 0; 3168 3169 /* 3170 * Calculate the chain hash: it's the combined hash of all the 3171 * lock keys along the dependency chain. We save the hash value 3172 * at every step so that we can get the current hash easily 3173 * after unlock. The chain hash is then used to cache dependency 3174 * results. 3175 * 3176 * The 'key ID' is what is the most compact key value to drive 3177 * the hash, not class->key. 3178 */ 3179 id = class - lock_classes; 3180 /* 3181 * Whoops, we did it again.. ran straight out of our static allocation. 3182 */ 3183 if (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS)) 3184 return 0; 3185 3186 chain_key = curr->curr_chain_key; 3187 if (!depth) { 3188 /* 3189 * How can we have a chain hash when we ain't got no keys?! 3190 */ 3191 if (DEBUG_LOCKS_WARN_ON(chain_key != 0)) 3192 return 0; 3193 chain_head = 1; 3194 } 3195 3196 hlock->prev_chain_key = chain_key; 3197 if (separate_irq_context(curr, hlock)) { 3198 chain_key = 0; 3199 chain_head = 1; 3200 } 3201 chain_key = iterate_chain_key(chain_key, id); 3202 3203 if (nest_lock && !__lock_is_held(nest_lock)) 3204 return print_lock_nested_lock_not_held(curr, hlock, ip); 3205 3206 if (!validate_chain(curr, lock, hlock, chain_head, chain_key)) 3207 return 0; 3208 3209 curr->curr_chain_key = chain_key; 3210 curr->lockdep_depth++; 3211 check_chain_key(curr); 3212 #ifdef CONFIG_DEBUG_LOCKDEP 3213 if (unlikely(!debug_locks)) 3214 return 0; 3215 #endif 3216 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) { 3217 debug_locks_off(); 3218 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!"); 3219 printk(KERN_DEBUG "depth: %i max: %lu!\n", 3220 curr->lockdep_depth, MAX_LOCK_DEPTH); 3221 3222 lockdep_print_held_locks(current); 3223 debug_show_all_locks(); 3224 dump_stack(); 3225 3226 return 0; 3227 } 3228 3229 if (unlikely(curr->lockdep_depth > max_lockdep_depth)) 3230 max_lockdep_depth = curr->lockdep_depth; 3231 3232 return 1; 3233 } 3234 3235 static int 3236 print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock, 3237 unsigned long ip) 3238 { 3239 if (!debug_locks_off()) 3240 return 0; 3241 if (debug_locks_silent) 3242 return 0; 3243 3244 printk("\n"); 3245 printk("=====================================\n"); 3246 printk("[ BUG: bad unlock balance detected! ]\n"); 3247 print_kernel_ident(); 3248 printk("-------------------------------------\n"); 3249 printk("%s/%d is trying to release lock (", 3250 curr->comm, task_pid_nr(curr)); 3251 print_lockdep_cache(lock); 3252 printk(") at:\n"); 3253 print_ip_sym(ip); 3254 printk("but there are no more locks to release!\n"); 3255 printk("\nother info that might help us debug this:\n"); 3256 lockdep_print_held_locks(curr); 3257 3258 printk("\nstack backtrace:\n"); 3259 dump_stack(); 3260 3261 return 0; 3262 } 3263 3264 static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock) 3265 { 3266 if (hlock->instance == lock) 3267 return 1; 3268 3269 if (hlock->references) { 3270 struct lock_class *class = lock->class_cache[0]; 3271 3272 if (!class) 3273 class = look_up_lock_class(lock, 0); 3274 3275 /* 3276 * If look_up_lock_class() failed to find a class, we're trying 3277 * to test if we hold a lock that has never yet been acquired. 3278 * Clearly if the lock hasn't been acquired _ever_, we're not 3279 * holding it either, so report failure. 3280 */ 3281 if (!class) 3282 return 0; 3283 3284 /* 3285 * References, but not a lock we're actually ref-counting? 3286 * State got messed up, follow the sites that change ->references 3287 * and try to make sense of it. 3288 */ 3289 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock)) 3290 return 0; 3291 3292 if (hlock->class_idx == class - lock_classes + 1) 3293 return 1; 3294 } 3295 3296 return 0; 3297 } 3298 3299 static int 3300 __lock_set_class(struct lockdep_map *lock, const char *name, 3301 struct lock_class_key *key, unsigned int subclass, 3302 unsigned long ip) 3303 { 3304 struct task_struct *curr = current; 3305 struct held_lock *hlock, *prev_hlock; 3306 struct lock_class *class; 3307 unsigned int depth; 3308 int i; 3309 3310 depth = curr->lockdep_depth; 3311 /* 3312 * This function is about (re)setting the class of a held lock, 3313 * yet we're not actually holding any locks. Naughty user! 3314 */ 3315 if (DEBUG_LOCKS_WARN_ON(!depth)) 3316 return 0; 3317 3318 prev_hlock = NULL; 3319 for (i = depth-1; i >= 0; i--) { 3320 hlock = curr->held_locks + i; 3321 /* 3322 * We must not cross into another context: 3323 */ 3324 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context) 3325 break; 3326 if (match_held_lock(hlock, lock)) 3327 goto found_it; 3328 prev_hlock = hlock; 3329 } 3330 return print_unlock_imbalance_bug(curr, lock, ip); 3331 3332 found_it: 3333 lockdep_init_map(lock, name, key, 0); 3334 class = register_lock_class(lock, subclass, 0); 3335 hlock->class_idx = class - lock_classes + 1; 3336 3337 curr->lockdep_depth = i; 3338 curr->curr_chain_key = hlock->prev_chain_key; 3339 3340 for (; i < depth; i++) { 3341 hlock = curr->held_locks + i; 3342 if (!__lock_acquire(hlock->instance, 3343 hlock_class(hlock)->subclass, hlock->trylock, 3344 hlock->read, hlock->check, hlock->hardirqs_off, 3345 hlock->nest_lock, hlock->acquire_ip, 3346 hlock->references, hlock->pin_count)) 3347 return 0; 3348 } 3349 3350 /* 3351 * I took it apart and put it back together again, except now I have 3352 * these 'spare' parts.. where shall I put them. 3353 */ 3354 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth)) 3355 return 0; 3356 return 1; 3357 } 3358 3359 /* 3360 * Remove the lock to the list of currently held locks - this gets 3361 * called on mutex_unlock()/spin_unlock*() (or on a failed 3362 * mutex_lock_interruptible()). 3363 * 3364 * @nested is an hysterical artifact, needs a tree wide cleanup. 3365 */ 3366 static int 3367 __lock_release(struct lockdep_map *lock, int nested, unsigned long ip) 3368 { 3369 struct task_struct *curr = current; 3370 struct held_lock *hlock, *prev_hlock; 3371 unsigned int depth; 3372 int i; 3373 3374 if (unlikely(!debug_locks)) 3375 return 0; 3376 3377 depth = curr->lockdep_depth; 3378 /* 3379 * So we're all set to release this lock.. wait what lock? We don't 3380 * own any locks, you've been drinking again? 3381 */ 3382 if (DEBUG_LOCKS_WARN_ON(depth <= 0)) 3383 return print_unlock_imbalance_bug(curr, lock, ip); 3384 3385 /* 3386 * Check whether the lock exists in the current stack 3387 * of held locks: 3388 */ 3389 prev_hlock = NULL; 3390 for (i = depth-1; i >= 0; i--) { 3391 hlock = curr->held_locks + i; 3392 /* 3393 * We must not cross into another context: 3394 */ 3395 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context) 3396 break; 3397 if (match_held_lock(hlock, lock)) 3398 goto found_it; 3399 prev_hlock = hlock; 3400 } 3401 return print_unlock_imbalance_bug(curr, lock, ip); 3402 3403 found_it: 3404 if (hlock->instance == lock) 3405 lock_release_holdtime(hlock); 3406 3407 WARN(hlock->pin_count, "releasing a pinned lock\n"); 3408 3409 if (hlock->references) { 3410 hlock->references--; 3411 if (hlock->references) { 3412 /* 3413 * We had, and after removing one, still have 3414 * references, the current lock stack is still 3415 * valid. We're done! 3416 */ 3417 return 1; 3418 } 3419 } 3420 3421 /* 3422 * We have the right lock to unlock, 'hlock' points to it. 3423 * Now we remove it from the stack, and add back the other 3424 * entries (if any), recalculating the hash along the way: 3425 */ 3426 3427 curr->lockdep_depth = i; 3428 curr->curr_chain_key = hlock->prev_chain_key; 3429 3430 for (i++; i < depth; i++) { 3431 hlock = curr->held_locks + i; 3432 if (!__lock_acquire(hlock->instance, 3433 hlock_class(hlock)->subclass, hlock->trylock, 3434 hlock->read, hlock->check, hlock->hardirqs_off, 3435 hlock->nest_lock, hlock->acquire_ip, 3436 hlock->references, hlock->pin_count)) 3437 return 0; 3438 } 3439 3440 /* 3441 * We had N bottles of beer on the wall, we drank one, but now 3442 * there's not N-1 bottles of beer left on the wall... 3443 */ 3444 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1)) 3445 return 0; 3446 3447 return 1; 3448 } 3449 3450 static int __lock_is_held(struct lockdep_map *lock) 3451 { 3452 struct task_struct *curr = current; 3453 int i; 3454 3455 for (i = 0; i < curr->lockdep_depth; i++) { 3456 struct held_lock *hlock = curr->held_locks + i; 3457 3458 if (match_held_lock(hlock, lock)) 3459 return 1; 3460 } 3461 3462 return 0; 3463 } 3464 3465 static void __lock_pin_lock(struct lockdep_map *lock) 3466 { 3467 struct task_struct *curr = current; 3468 int i; 3469 3470 if (unlikely(!debug_locks)) 3471 return; 3472 3473 for (i = 0; i < curr->lockdep_depth; i++) { 3474 struct held_lock *hlock = curr->held_locks + i; 3475 3476 if (match_held_lock(hlock, lock)) { 3477 hlock->pin_count++; 3478 return; 3479 } 3480 } 3481 3482 WARN(1, "pinning an unheld lock\n"); 3483 } 3484 3485 static void __lock_unpin_lock(struct lockdep_map *lock) 3486 { 3487 struct task_struct *curr = current; 3488 int i; 3489 3490 if (unlikely(!debug_locks)) 3491 return; 3492 3493 for (i = 0; i < curr->lockdep_depth; i++) { 3494 struct held_lock *hlock = curr->held_locks + i; 3495 3496 if (match_held_lock(hlock, lock)) { 3497 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n")) 3498 return; 3499 3500 hlock->pin_count--; 3501 return; 3502 } 3503 } 3504 3505 WARN(1, "unpinning an unheld lock\n"); 3506 } 3507 3508 /* 3509 * Check whether we follow the irq-flags state precisely: 3510 */ 3511 static void check_flags(unsigned long flags) 3512 { 3513 #if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \ 3514 defined(CONFIG_TRACE_IRQFLAGS) 3515 if (!debug_locks) 3516 return; 3517 3518 if (irqs_disabled_flags(flags)) { 3519 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) { 3520 printk("possible reason: unannotated irqs-off.\n"); 3521 } 3522 } else { 3523 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) { 3524 printk("possible reason: unannotated irqs-on.\n"); 3525 } 3526 } 3527 3528 /* 3529 * We dont accurately track softirq state in e.g. 3530 * hardirq contexts (such as on 4KSTACKS), so only 3531 * check if not in hardirq contexts: 3532 */ 3533 if (!hardirq_count()) { 3534 if (softirq_count()) { 3535 /* like the above, but with softirqs */ 3536 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled); 3537 } else { 3538 /* lick the above, does it taste good? */ 3539 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled); 3540 } 3541 } 3542 3543 if (!debug_locks) 3544 print_irqtrace_events(current); 3545 #endif 3546 } 3547 3548 void lock_set_class(struct lockdep_map *lock, const char *name, 3549 struct lock_class_key *key, unsigned int subclass, 3550 unsigned long ip) 3551 { 3552 unsigned long flags; 3553 3554 if (unlikely(current->lockdep_recursion)) 3555 return; 3556 3557 raw_local_irq_save(flags); 3558 current->lockdep_recursion = 1; 3559 check_flags(flags); 3560 if (__lock_set_class(lock, name, key, subclass, ip)) 3561 check_chain_key(current); 3562 current->lockdep_recursion = 0; 3563 raw_local_irq_restore(flags); 3564 } 3565 EXPORT_SYMBOL_GPL(lock_set_class); 3566 3567 /* 3568 * We are not always called with irqs disabled - do that here, 3569 * and also avoid lockdep recursion: 3570 */ 3571 void lock_acquire(struct lockdep_map *lock, unsigned int subclass, 3572 int trylock, int read, int check, 3573 struct lockdep_map *nest_lock, unsigned long ip) 3574 { 3575 unsigned long flags; 3576 3577 if (unlikely(current->lockdep_recursion)) 3578 return; 3579 3580 raw_local_irq_save(flags); 3581 check_flags(flags); 3582 3583 current->lockdep_recursion = 1; 3584 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip); 3585 __lock_acquire(lock, subclass, trylock, read, check, 3586 irqs_disabled_flags(flags), nest_lock, ip, 0, 0); 3587 current->lockdep_recursion = 0; 3588 raw_local_irq_restore(flags); 3589 } 3590 EXPORT_SYMBOL_GPL(lock_acquire); 3591 3592 void lock_release(struct lockdep_map *lock, int nested, 3593 unsigned long ip) 3594 { 3595 unsigned long flags; 3596 3597 if (unlikely(current->lockdep_recursion)) 3598 return; 3599 3600 raw_local_irq_save(flags); 3601 check_flags(flags); 3602 current->lockdep_recursion = 1; 3603 trace_lock_release(lock, ip); 3604 if (__lock_release(lock, nested, ip)) 3605 check_chain_key(current); 3606 current->lockdep_recursion = 0; 3607 raw_local_irq_restore(flags); 3608 } 3609 EXPORT_SYMBOL_GPL(lock_release); 3610 3611 int lock_is_held(struct lockdep_map *lock) 3612 { 3613 unsigned long flags; 3614 int ret = 0; 3615 3616 if (unlikely(current->lockdep_recursion)) 3617 return 1; /* avoid false negative lockdep_assert_held() */ 3618 3619 raw_local_irq_save(flags); 3620 check_flags(flags); 3621 3622 current->lockdep_recursion = 1; 3623 ret = __lock_is_held(lock); 3624 current->lockdep_recursion = 0; 3625 raw_local_irq_restore(flags); 3626 3627 return ret; 3628 } 3629 EXPORT_SYMBOL_GPL(lock_is_held); 3630 3631 void lock_pin_lock(struct lockdep_map *lock) 3632 { 3633 unsigned long flags; 3634 3635 if (unlikely(current->lockdep_recursion)) 3636 return; 3637 3638 raw_local_irq_save(flags); 3639 check_flags(flags); 3640 3641 current->lockdep_recursion = 1; 3642 __lock_pin_lock(lock); 3643 current->lockdep_recursion = 0; 3644 raw_local_irq_restore(flags); 3645 } 3646 EXPORT_SYMBOL_GPL(lock_pin_lock); 3647 3648 void lock_unpin_lock(struct lockdep_map *lock) 3649 { 3650 unsigned long flags; 3651 3652 if (unlikely(current->lockdep_recursion)) 3653 return; 3654 3655 raw_local_irq_save(flags); 3656 check_flags(flags); 3657 3658 current->lockdep_recursion = 1; 3659 __lock_unpin_lock(lock); 3660 current->lockdep_recursion = 0; 3661 raw_local_irq_restore(flags); 3662 } 3663 EXPORT_SYMBOL_GPL(lock_unpin_lock); 3664 3665 void lockdep_set_current_reclaim_state(gfp_t gfp_mask) 3666 { 3667 current->lockdep_reclaim_gfp = gfp_mask; 3668 } 3669 3670 void lockdep_clear_current_reclaim_state(void) 3671 { 3672 current->lockdep_reclaim_gfp = 0; 3673 } 3674 3675 #ifdef CONFIG_LOCK_STAT 3676 static int 3677 print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock, 3678 unsigned long ip) 3679 { 3680 if (!debug_locks_off()) 3681 return 0; 3682 if (debug_locks_silent) 3683 return 0; 3684 3685 printk("\n"); 3686 printk("=================================\n"); 3687 printk("[ BUG: bad contention detected! ]\n"); 3688 print_kernel_ident(); 3689 printk("---------------------------------\n"); 3690 printk("%s/%d is trying to contend lock (", 3691 curr->comm, task_pid_nr(curr)); 3692 print_lockdep_cache(lock); 3693 printk(") at:\n"); 3694 print_ip_sym(ip); 3695 printk("but there are no locks held!\n"); 3696 printk("\nother info that might help us debug this:\n"); 3697 lockdep_print_held_locks(curr); 3698 3699 printk("\nstack backtrace:\n"); 3700 dump_stack(); 3701 3702 return 0; 3703 } 3704 3705 static void 3706 __lock_contended(struct lockdep_map *lock, unsigned long ip) 3707 { 3708 struct task_struct *curr = current; 3709 struct held_lock *hlock, *prev_hlock; 3710 struct lock_class_stats *stats; 3711 unsigned int depth; 3712 int i, contention_point, contending_point; 3713 3714 depth = curr->lockdep_depth; 3715 /* 3716 * Whee, we contended on this lock, except it seems we're not 3717 * actually trying to acquire anything much at all.. 3718 */ 3719 if (DEBUG_LOCKS_WARN_ON(!depth)) 3720 return; 3721 3722 prev_hlock = NULL; 3723 for (i = depth-1; i >= 0; i--) { 3724 hlock = curr->held_locks + i; 3725 /* 3726 * We must not cross into another context: 3727 */ 3728 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context) 3729 break; 3730 if (match_held_lock(hlock, lock)) 3731 goto found_it; 3732 prev_hlock = hlock; 3733 } 3734 print_lock_contention_bug(curr, lock, ip); 3735 return; 3736 3737 found_it: 3738 if (hlock->instance != lock) 3739 return; 3740 3741 hlock->waittime_stamp = lockstat_clock(); 3742 3743 contention_point = lock_point(hlock_class(hlock)->contention_point, ip); 3744 contending_point = lock_point(hlock_class(hlock)->contending_point, 3745 lock->ip); 3746 3747 stats = get_lock_stats(hlock_class(hlock)); 3748 if (contention_point < LOCKSTAT_POINTS) 3749 stats->contention_point[contention_point]++; 3750 if (contending_point < LOCKSTAT_POINTS) 3751 stats->contending_point[contending_point]++; 3752 if (lock->cpu != smp_processor_id()) 3753 stats->bounces[bounce_contended + !!hlock->read]++; 3754 put_lock_stats(stats); 3755 } 3756 3757 static void 3758 __lock_acquired(struct lockdep_map *lock, unsigned long ip) 3759 { 3760 struct task_struct *curr = current; 3761 struct held_lock *hlock, *prev_hlock; 3762 struct lock_class_stats *stats; 3763 unsigned int depth; 3764 u64 now, waittime = 0; 3765 int i, cpu; 3766 3767 depth = curr->lockdep_depth; 3768 /* 3769 * Yay, we acquired ownership of this lock we didn't try to 3770 * acquire, how the heck did that happen? 3771 */ 3772 if (DEBUG_LOCKS_WARN_ON(!depth)) 3773 return; 3774 3775 prev_hlock = NULL; 3776 for (i = depth-1; i >= 0; i--) { 3777 hlock = curr->held_locks + i; 3778 /* 3779 * We must not cross into another context: 3780 */ 3781 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context) 3782 break; 3783 if (match_held_lock(hlock, lock)) 3784 goto found_it; 3785 prev_hlock = hlock; 3786 } 3787 print_lock_contention_bug(curr, lock, _RET_IP_); 3788 return; 3789 3790 found_it: 3791 if (hlock->instance != lock) 3792 return; 3793 3794 cpu = smp_processor_id(); 3795 if (hlock->waittime_stamp) { 3796 now = lockstat_clock(); 3797 waittime = now - hlock->waittime_stamp; 3798 hlock->holdtime_stamp = now; 3799 } 3800 3801 trace_lock_acquired(lock, ip); 3802 3803 stats = get_lock_stats(hlock_class(hlock)); 3804 if (waittime) { 3805 if (hlock->read) 3806 lock_time_inc(&stats->read_waittime, waittime); 3807 else 3808 lock_time_inc(&stats->write_waittime, waittime); 3809 } 3810 if (lock->cpu != cpu) 3811 stats->bounces[bounce_acquired + !!hlock->read]++; 3812 put_lock_stats(stats); 3813 3814 lock->cpu = cpu; 3815 lock->ip = ip; 3816 } 3817 3818 void lock_contended(struct lockdep_map *lock, unsigned long ip) 3819 { 3820 unsigned long flags; 3821 3822 if (unlikely(!lock_stat)) 3823 return; 3824 3825 if (unlikely(current->lockdep_recursion)) 3826 return; 3827 3828 raw_local_irq_save(flags); 3829 check_flags(flags); 3830 current->lockdep_recursion = 1; 3831 trace_lock_contended(lock, ip); 3832 __lock_contended(lock, ip); 3833 current->lockdep_recursion = 0; 3834 raw_local_irq_restore(flags); 3835 } 3836 EXPORT_SYMBOL_GPL(lock_contended); 3837 3838 void lock_acquired(struct lockdep_map *lock, unsigned long ip) 3839 { 3840 unsigned long flags; 3841 3842 if (unlikely(!lock_stat)) 3843 return; 3844 3845 if (unlikely(current->lockdep_recursion)) 3846 return; 3847 3848 raw_local_irq_save(flags); 3849 check_flags(flags); 3850 current->lockdep_recursion = 1; 3851 __lock_acquired(lock, ip); 3852 current->lockdep_recursion = 0; 3853 raw_local_irq_restore(flags); 3854 } 3855 EXPORT_SYMBOL_GPL(lock_acquired); 3856 #endif 3857 3858 /* 3859 * Used by the testsuite, sanitize the validator state 3860 * after a simulated failure: 3861 */ 3862 3863 void lockdep_reset(void) 3864 { 3865 unsigned long flags; 3866 int i; 3867 3868 raw_local_irq_save(flags); 3869 current->curr_chain_key = 0; 3870 current->lockdep_depth = 0; 3871 current->lockdep_recursion = 0; 3872 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock)); 3873 nr_hardirq_chains = 0; 3874 nr_softirq_chains = 0; 3875 nr_process_chains = 0; 3876 debug_locks = 1; 3877 for (i = 0; i < CHAINHASH_SIZE; i++) 3878 INIT_LIST_HEAD(chainhash_table + i); 3879 raw_local_irq_restore(flags); 3880 } 3881 3882 static void zap_class(struct lock_class *class) 3883 { 3884 int i; 3885 3886 /* 3887 * Remove all dependencies this lock is 3888 * involved in: 3889 */ 3890 for (i = 0; i < nr_list_entries; i++) { 3891 if (list_entries[i].class == class) 3892 list_del_rcu(&list_entries[i].entry); 3893 } 3894 /* 3895 * Unhash the class and remove it from the all_lock_classes list: 3896 */ 3897 list_del_rcu(&class->hash_entry); 3898 list_del_rcu(&class->lock_entry); 3899 3900 RCU_INIT_POINTER(class->key, NULL); 3901 RCU_INIT_POINTER(class->name, NULL); 3902 } 3903 3904 static inline int within(const void *addr, void *start, unsigned long size) 3905 { 3906 return addr >= start && addr < start + size; 3907 } 3908 3909 /* 3910 * Used in module.c to remove lock classes from memory that is going to be 3911 * freed; and possibly re-used by other modules. 3912 * 3913 * We will have had one sync_sched() before getting here, so we're guaranteed 3914 * nobody will look up these exact classes -- they're properly dead but still 3915 * allocated. 3916 */ 3917 void lockdep_free_key_range(void *start, unsigned long size) 3918 { 3919 struct lock_class *class; 3920 struct list_head *head; 3921 unsigned long flags; 3922 int i; 3923 int locked; 3924 3925 raw_local_irq_save(flags); 3926 locked = graph_lock(); 3927 3928 /* 3929 * Unhash all classes that were created by this module: 3930 */ 3931 for (i = 0; i < CLASSHASH_SIZE; i++) { 3932 head = classhash_table + i; 3933 if (list_empty(head)) 3934 continue; 3935 list_for_each_entry_rcu(class, head, hash_entry) { 3936 if (within(class->key, start, size)) 3937 zap_class(class); 3938 else if (within(class->name, start, size)) 3939 zap_class(class); 3940 } 3941 } 3942 3943 if (locked) 3944 graph_unlock(); 3945 raw_local_irq_restore(flags); 3946 3947 /* 3948 * Wait for any possible iterators from look_up_lock_class() to pass 3949 * before continuing to free the memory they refer to. 3950 * 3951 * sync_sched() is sufficient because the read-side is IRQ disable. 3952 */ 3953 synchronize_sched(); 3954 3955 /* 3956 * XXX at this point we could return the resources to the pool; 3957 * instead we leak them. We would need to change to bitmap allocators 3958 * instead of the linear allocators we have now. 3959 */ 3960 } 3961 3962 void lockdep_reset_lock(struct lockdep_map *lock) 3963 { 3964 struct lock_class *class; 3965 struct list_head *head; 3966 unsigned long flags; 3967 int i, j; 3968 int locked; 3969 3970 raw_local_irq_save(flags); 3971 3972 /* 3973 * Remove all classes this lock might have: 3974 */ 3975 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) { 3976 /* 3977 * If the class exists we look it up and zap it: 3978 */ 3979 class = look_up_lock_class(lock, j); 3980 if (class) 3981 zap_class(class); 3982 } 3983 /* 3984 * Debug check: in the end all mapped classes should 3985 * be gone. 3986 */ 3987 locked = graph_lock(); 3988 for (i = 0; i < CLASSHASH_SIZE; i++) { 3989 head = classhash_table + i; 3990 if (list_empty(head)) 3991 continue; 3992 list_for_each_entry_rcu(class, head, hash_entry) { 3993 int match = 0; 3994 3995 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++) 3996 match |= class == lock->class_cache[j]; 3997 3998 if (unlikely(match)) { 3999 if (debug_locks_off_graph_unlock()) { 4000 /* 4001 * We all just reset everything, how did it match? 4002 */ 4003 WARN_ON(1); 4004 } 4005 goto out_restore; 4006 } 4007 } 4008 } 4009 if (locked) 4010 graph_unlock(); 4011 4012 out_restore: 4013 raw_local_irq_restore(flags); 4014 } 4015 4016 void lockdep_init(void) 4017 { 4018 int i; 4019 4020 /* 4021 * Some architectures have their own start_kernel() 4022 * code which calls lockdep_init(), while we also 4023 * call lockdep_init() from the start_kernel() itself, 4024 * and we want to initialize the hashes only once: 4025 */ 4026 if (lockdep_initialized) 4027 return; 4028 4029 for (i = 0; i < CLASSHASH_SIZE; i++) 4030 INIT_LIST_HEAD(classhash_table + i); 4031 4032 for (i = 0; i < CHAINHASH_SIZE; i++) 4033 INIT_LIST_HEAD(chainhash_table + i); 4034 4035 lockdep_initialized = 1; 4036 } 4037 4038 void __init lockdep_info(void) 4039 { 4040 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n"); 4041 4042 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES); 4043 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH); 4044 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS); 4045 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE); 4046 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES); 4047 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS); 4048 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE); 4049 4050 printk(" memory used by lock dependency info: %lu kB\n", 4051 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS + 4052 sizeof(struct list_head) * CLASSHASH_SIZE + 4053 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES + 4054 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS + 4055 sizeof(struct list_head) * CHAINHASH_SIZE 4056 #ifdef CONFIG_PROVE_LOCKING 4057 + sizeof(struct circular_queue) 4058 #endif 4059 ) / 1024 4060 ); 4061 4062 printk(" per task-struct memory footprint: %lu bytes\n", 4063 sizeof(struct held_lock) * MAX_LOCK_DEPTH); 4064 4065 #ifdef CONFIG_DEBUG_LOCKDEP 4066 if (lockdep_init_error) { 4067 printk("WARNING: lockdep init error: lock '%s' was acquired before lockdep_init().\n", lock_init_error); 4068 printk("Call stack leading to lockdep invocation was:\n"); 4069 print_stack_trace(&lockdep_init_trace, 0); 4070 } 4071 #endif 4072 } 4073 4074 static void 4075 print_freed_lock_bug(struct task_struct *curr, const void *mem_from, 4076 const void *mem_to, struct held_lock *hlock) 4077 { 4078 if (!debug_locks_off()) 4079 return; 4080 if (debug_locks_silent) 4081 return; 4082 4083 printk("\n"); 4084 printk("=========================\n"); 4085 printk("[ BUG: held lock freed! ]\n"); 4086 print_kernel_ident(); 4087 printk("-------------------------\n"); 4088 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n", 4089 curr->comm, task_pid_nr(curr), mem_from, mem_to-1); 4090 print_lock(hlock); 4091 lockdep_print_held_locks(curr); 4092 4093 printk("\nstack backtrace:\n"); 4094 dump_stack(); 4095 } 4096 4097 static inline int not_in_range(const void* mem_from, unsigned long mem_len, 4098 const void* lock_from, unsigned long lock_len) 4099 { 4100 return lock_from + lock_len <= mem_from || 4101 mem_from + mem_len <= lock_from; 4102 } 4103 4104 /* 4105 * Called when kernel memory is freed (or unmapped), or if a lock 4106 * is destroyed or reinitialized - this code checks whether there is 4107 * any held lock in the memory range of <from> to <to>: 4108 */ 4109 void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len) 4110 { 4111 struct task_struct *curr = current; 4112 struct held_lock *hlock; 4113 unsigned long flags; 4114 int i; 4115 4116 if (unlikely(!debug_locks)) 4117 return; 4118 4119 local_irq_save(flags); 4120 for (i = 0; i < curr->lockdep_depth; i++) { 4121 hlock = curr->held_locks + i; 4122 4123 if (not_in_range(mem_from, mem_len, hlock->instance, 4124 sizeof(*hlock->instance))) 4125 continue; 4126 4127 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock); 4128 break; 4129 } 4130 local_irq_restore(flags); 4131 } 4132 EXPORT_SYMBOL_GPL(debug_check_no_locks_freed); 4133 4134 static void print_held_locks_bug(void) 4135 { 4136 if (!debug_locks_off()) 4137 return; 4138 if (debug_locks_silent) 4139 return; 4140 4141 printk("\n"); 4142 printk("=====================================\n"); 4143 printk("[ BUG: %s/%d still has locks held! ]\n", 4144 current->comm, task_pid_nr(current)); 4145 print_kernel_ident(); 4146 printk("-------------------------------------\n"); 4147 lockdep_print_held_locks(current); 4148 printk("\nstack backtrace:\n"); 4149 dump_stack(); 4150 } 4151 4152 void debug_check_no_locks_held(void) 4153 { 4154 if (unlikely(current->lockdep_depth > 0)) 4155 print_held_locks_bug(); 4156 } 4157 EXPORT_SYMBOL_GPL(debug_check_no_locks_held); 4158 4159 #ifdef __KERNEL__ 4160 void debug_show_all_locks(void) 4161 { 4162 struct task_struct *g, *p; 4163 int count = 10; 4164 int unlock = 1; 4165 4166 if (unlikely(!debug_locks)) { 4167 printk("INFO: lockdep is turned off.\n"); 4168 return; 4169 } 4170 printk("\nShowing all locks held in the system:\n"); 4171 4172 /* 4173 * Here we try to get the tasklist_lock as hard as possible, 4174 * if not successful after 2 seconds we ignore it (but keep 4175 * trying). This is to enable a debug printout even if a 4176 * tasklist_lock-holding task deadlocks or crashes. 4177 */ 4178 retry: 4179 if (!read_trylock(&tasklist_lock)) { 4180 if (count == 10) 4181 printk("hm, tasklist_lock locked, retrying... "); 4182 if (count) { 4183 count--; 4184 printk(" #%d", 10-count); 4185 mdelay(200); 4186 goto retry; 4187 } 4188 printk(" ignoring it.\n"); 4189 unlock = 0; 4190 } else { 4191 if (count != 10) 4192 printk(KERN_CONT " locked it.\n"); 4193 } 4194 4195 do_each_thread(g, p) { 4196 /* 4197 * It's not reliable to print a task's held locks 4198 * if it's not sleeping (or if it's not the current 4199 * task): 4200 */ 4201 if (p->state == TASK_RUNNING && p != current) 4202 continue; 4203 if (p->lockdep_depth) 4204 lockdep_print_held_locks(p); 4205 if (!unlock) 4206 if (read_trylock(&tasklist_lock)) 4207 unlock = 1; 4208 } while_each_thread(g, p); 4209 4210 printk("\n"); 4211 printk("=============================================\n\n"); 4212 4213 if (unlock) 4214 read_unlock(&tasklist_lock); 4215 } 4216 EXPORT_SYMBOL_GPL(debug_show_all_locks); 4217 #endif 4218 4219 /* 4220 * Careful: only use this function if you are sure that 4221 * the task cannot run in parallel! 4222 */ 4223 void debug_show_held_locks(struct task_struct *task) 4224 { 4225 if (unlikely(!debug_locks)) { 4226 printk("INFO: lockdep is turned off.\n"); 4227 return; 4228 } 4229 lockdep_print_held_locks(task); 4230 } 4231 EXPORT_SYMBOL_GPL(debug_show_held_locks); 4232 4233 asmlinkage __visible void lockdep_sys_exit(void) 4234 { 4235 struct task_struct *curr = current; 4236 4237 if (unlikely(curr->lockdep_depth)) { 4238 if (!debug_locks_off()) 4239 return; 4240 printk("\n"); 4241 printk("================================================\n"); 4242 printk("[ BUG: lock held when returning to user space! ]\n"); 4243 print_kernel_ident(); 4244 printk("------------------------------------------------\n"); 4245 printk("%s/%d is leaving the kernel with locks still held!\n", 4246 curr->comm, curr->pid); 4247 lockdep_print_held_locks(curr); 4248 } 4249 } 4250 4251 void lockdep_rcu_suspicious(const char *file, const int line, const char *s) 4252 { 4253 struct task_struct *curr = current; 4254 4255 #ifndef CONFIG_PROVE_RCU_REPEATEDLY 4256 if (!debug_locks_off()) 4257 return; 4258 #endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */ 4259 /* Note: the following can be executed concurrently, so be careful. */ 4260 printk("\n"); 4261 printk("===============================\n"); 4262 printk("[ INFO: suspicious RCU usage. ]\n"); 4263 print_kernel_ident(); 4264 printk("-------------------------------\n"); 4265 printk("%s:%d %s!\n", file, line, s); 4266 printk("\nother info that might help us debug this:\n\n"); 4267 printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n", 4268 !rcu_lockdep_current_cpu_online() 4269 ? "RCU used illegally from offline CPU!\n" 4270 : !rcu_is_watching() 4271 ? "RCU used illegally from idle CPU!\n" 4272 : "", 4273 rcu_scheduler_active, debug_locks); 4274 4275 /* 4276 * If a CPU is in the RCU-free window in idle (ie: in the section 4277 * between rcu_idle_enter() and rcu_idle_exit(), then RCU 4278 * considers that CPU to be in an "extended quiescent state", 4279 * which means that RCU will be completely ignoring that CPU. 4280 * Therefore, rcu_read_lock() and friends have absolutely no 4281 * effect on a CPU running in that state. In other words, even if 4282 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well 4283 * delete data structures out from under it. RCU really has no 4284 * choice here: we need to keep an RCU-free window in idle where 4285 * the CPU may possibly enter into low power mode. This way we can 4286 * notice an extended quiescent state to other CPUs that started a grace 4287 * period. Otherwise we would delay any grace period as long as we run 4288 * in the idle task. 4289 * 4290 * So complain bitterly if someone does call rcu_read_lock(), 4291 * rcu_read_lock_bh() and so on from extended quiescent states. 4292 */ 4293 if (!rcu_is_watching()) 4294 printk("RCU used illegally from extended quiescent state!\n"); 4295 4296 lockdep_print_held_locks(curr); 4297 printk("\nstack backtrace:\n"); 4298 dump_stack(); 4299 } 4300 EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious); 4301