1 /* 2 * trace task wakeup timings 3 * 4 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> 5 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com> 6 * 7 * Based on code from the latency_tracer, that is: 8 * 9 * Copyright (C) 2004-2006 Ingo Molnar 10 * Copyright (C) 2004 Nadia Yvette Chambers 11 */ 12 #include <linux/module.h> 13 #include <linux/fs.h> 14 #include <linux/debugfs.h> 15 #include <linux/kallsyms.h> 16 #include <linux/uaccess.h> 17 #include <linux/ftrace.h> 18 #include <linux/sched/rt.h> 19 #include <trace/events/sched.h> 20 #include "trace.h" 21 22 static struct trace_array *wakeup_trace; 23 static int __read_mostly tracer_enabled; 24 25 static struct task_struct *wakeup_task; 26 static int wakeup_cpu; 27 static int wakeup_current_cpu; 28 static unsigned wakeup_prio = -1; 29 static int wakeup_rt; 30 31 static arch_spinlock_t wakeup_lock = 32 (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; 33 34 static void wakeup_reset(struct trace_array *tr); 35 static void __wakeup_reset(struct trace_array *tr); 36 static int wakeup_graph_entry(struct ftrace_graph_ent *trace); 37 static void wakeup_graph_return(struct ftrace_graph_ret *trace); 38 39 static int save_flags; 40 static bool function_enabled; 41 42 #define TRACE_DISPLAY_GRAPH 1 43 44 static struct tracer_opt trace_opts[] = { 45 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 46 /* display latency trace as call graph */ 47 { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) }, 48 #endif 49 { } /* Empty entry */ 50 }; 51 52 static struct tracer_flags tracer_flags = { 53 .val = 0, 54 .opts = trace_opts, 55 }; 56 57 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH) 58 59 #ifdef CONFIG_FUNCTION_TRACER 60 61 /* 62 * Prologue for the wakeup function tracers. 63 * 64 * Returns 1 if it is OK to continue, and preemption 65 * is disabled and data->disabled is incremented. 66 * 0 if the trace is to be ignored, and preemption 67 * is not disabled and data->disabled is 68 * kept the same. 69 * 70 * Note, this function is also used outside this ifdef but 71 * inside the #ifdef of the function graph tracer below. 72 * This is OK, since the function graph tracer is 73 * dependent on the function tracer. 74 */ 75 static int 76 func_prolog_preempt_disable(struct trace_array *tr, 77 struct trace_array_cpu **data, 78 int *pc) 79 { 80 long disabled; 81 int cpu; 82 83 if (likely(!wakeup_task)) 84 return 0; 85 86 *pc = preempt_count(); 87 preempt_disable_notrace(); 88 89 cpu = raw_smp_processor_id(); 90 if (cpu != wakeup_current_cpu) 91 goto out_enable; 92 93 *data = per_cpu_ptr(tr->trace_buffer.data, cpu); 94 disabled = atomic_inc_return(&(*data)->disabled); 95 if (unlikely(disabled != 1)) 96 goto out; 97 98 return 1; 99 100 out: 101 atomic_dec(&(*data)->disabled); 102 103 out_enable: 104 preempt_enable_notrace(); 105 return 0; 106 } 107 108 /* 109 * wakeup uses its own tracer function to keep the overhead down: 110 */ 111 static void 112 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip, 113 struct ftrace_ops *op, struct pt_regs *pt_regs) 114 { 115 struct trace_array *tr = wakeup_trace; 116 struct trace_array_cpu *data; 117 unsigned long flags; 118 int pc; 119 120 if (!func_prolog_preempt_disable(tr, &data, &pc)) 121 return; 122 123 local_irq_save(flags); 124 trace_function(tr, ip, parent_ip, flags, pc); 125 local_irq_restore(flags); 126 127 atomic_dec(&data->disabled); 128 preempt_enable_notrace(); 129 } 130 131 static struct ftrace_ops trace_ops __read_mostly = 132 { 133 .func = wakeup_tracer_call, 134 .flags = FTRACE_OPS_FL_GLOBAL | FTRACE_OPS_FL_RECURSION_SAFE, 135 }; 136 #endif /* CONFIG_FUNCTION_TRACER */ 137 138 static int register_wakeup_function(int graph, int set) 139 { 140 int ret; 141 142 /* 'set' is set if TRACE_ITER_FUNCTION is about to be set */ 143 if (function_enabled || (!set && !(trace_flags & TRACE_ITER_FUNCTION))) 144 return 0; 145 146 if (graph) 147 ret = register_ftrace_graph(&wakeup_graph_return, 148 &wakeup_graph_entry); 149 else 150 ret = register_ftrace_function(&trace_ops); 151 152 if (!ret) 153 function_enabled = true; 154 155 return ret; 156 } 157 158 static void unregister_wakeup_function(int graph) 159 { 160 if (!function_enabled) 161 return; 162 163 if (graph) 164 unregister_ftrace_graph(); 165 else 166 unregister_ftrace_function(&trace_ops); 167 168 function_enabled = false; 169 } 170 171 static void wakeup_function_set(int set) 172 { 173 if (set) 174 register_wakeup_function(is_graph(), 1); 175 else 176 unregister_wakeup_function(is_graph()); 177 } 178 179 static int wakeup_flag_changed(struct tracer *tracer, u32 mask, int set) 180 { 181 if (mask & TRACE_ITER_FUNCTION) 182 wakeup_function_set(set); 183 184 return trace_keep_overwrite(tracer, mask, set); 185 } 186 187 static int start_func_tracer(int graph) 188 { 189 int ret; 190 191 ret = register_wakeup_function(graph, 0); 192 193 if (!ret && tracing_is_enabled()) 194 tracer_enabled = 1; 195 else 196 tracer_enabled = 0; 197 198 return ret; 199 } 200 201 static void stop_func_tracer(int graph) 202 { 203 tracer_enabled = 0; 204 205 unregister_wakeup_function(graph); 206 } 207 208 #ifdef CONFIG_FUNCTION_GRAPH_TRACER 209 static int wakeup_set_flag(u32 old_flags, u32 bit, int set) 210 { 211 212 if (!(bit & TRACE_DISPLAY_GRAPH)) 213 return -EINVAL; 214 215 if (!(is_graph() ^ set)) 216 return 0; 217 218 stop_func_tracer(!set); 219 220 wakeup_reset(wakeup_trace); 221 tracing_max_latency = 0; 222 223 return start_func_tracer(set); 224 } 225 226 static int wakeup_graph_entry(struct ftrace_graph_ent *trace) 227 { 228 struct trace_array *tr = wakeup_trace; 229 struct trace_array_cpu *data; 230 unsigned long flags; 231 int pc, ret = 0; 232 233 if (!func_prolog_preempt_disable(tr, &data, &pc)) 234 return 0; 235 236 local_save_flags(flags); 237 ret = __trace_graph_entry(tr, trace, flags, pc); 238 atomic_dec(&data->disabled); 239 preempt_enable_notrace(); 240 241 return ret; 242 } 243 244 static void wakeup_graph_return(struct ftrace_graph_ret *trace) 245 { 246 struct trace_array *tr = wakeup_trace; 247 struct trace_array_cpu *data; 248 unsigned long flags; 249 int pc; 250 251 if (!func_prolog_preempt_disable(tr, &data, &pc)) 252 return; 253 254 local_save_flags(flags); 255 __trace_graph_return(tr, trace, flags, pc); 256 atomic_dec(&data->disabled); 257 258 preempt_enable_notrace(); 259 return; 260 } 261 262 static void wakeup_trace_open(struct trace_iterator *iter) 263 { 264 if (is_graph()) 265 graph_trace_open(iter); 266 } 267 268 static void wakeup_trace_close(struct trace_iterator *iter) 269 { 270 if (iter->private) 271 graph_trace_close(iter); 272 } 273 274 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC | \ 275 TRACE_GRAPH_PRINT_ABS_TIME | \ 276 TRACE_GRAPH_PRINT_DURATION) 277 278 static enum print_line_t wakeup_print_line(struct trace_iterator *iter) 279 { 280 /* 281 * In graph mode call the graph tracer output function, 282 * otherwise go with the TRACE_FN event handler 283 */ 284 if (is_graph()) 285 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS); 286 287 return TRACE_TYPE_UNHANDLED; 288 } 289 290 static void wakeup_print_header(struct seq_file *s) 291 { 292 if (is_graph()) 293 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS); 294 else 295 trace_default_header(s); 296 } 297 298 static void 299 __trace_function(struct trace_array *tr, 300 unsigned long ip, unsigned long parent_ip, 301 unsigned long flags, int pc) 302 { 303 if (is_graph()) 304 trace_graph_function(tr, ip, parent_ip, flags, pc); 305 else 306 trace_function(tr, ip, parent_ip, flags, pc); 307 } 308 #else 309 #define __trace_function trace_function 310 311 static int wakeup_set_flag(u32 old_flags, u32 bit, int set) 312 { 313 return -EINVAL; 314 } 315 316 static int wakeup_graph_entry(struct ftrace_graph_ent *trace) 317 { 318 return -1; 319 } 320 321 static enum print_line_t wakeup_print_line(struct trace_iterator *iter) 322 { 323 return TRACE_TYPE_UNHANDLED; 324 } 325 326 static void wakeup_graph_return(struct ftrace_graph_ret *trace) { } 327 static void wakeup_trace_open(struct trace_iterator *iter) { } 328 static void wakeup_trace_close(struct trace_iterator *iter) { } 329 330 #ifdef CONFIG_FUNCTION_TRACER 331 static void wakeup_print_header(struct seq_file *s) 332 { 333 trace_default_header(s); 334 } 335 #else 336 static void wakeup_print_header(struct seq_file *s) 337 { 338 trace_latency_header(s); 339 } 340 #endif /* CONFIG_FUNCTION_TRACER */ 341 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ 342 343 /* 344 * Should this new latency be reported/recorded? 345 */ 346 static int report_latency(cycle_t delta) 347 { 348 if (tracing_thresh) { 349 if (delta < tracing_thresh) 350 return 0; 351 } else { 352 if (delta <= tracing_max_latency) 353 return 0; 354 } 355 return 1; 356 } 357 358 static void 359 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu) 360 { 361 if (task != wakeup_task) 362 return; 363 364 wakeup_current_cpu = cpu; 365 } 366 367 static void notrace 368 probe_wakeup_sched_switch(void *ignore, 369 struct task_struct *prev, struct task_struct *next) 370 { 371 struct trace_array_cpu *data; 372 cycle_t T0, T1, delta; 373 unsigned long flags; 374 long disabled; 375 int cpu; 376 int pc; 377 378 tracing_record_cmdline(prev); 379 380 if (unlikely(!tracer_enabled)) 381 return; 382 383 /* 384 * When we start a new trace, we set wakeup_task to NULL 385 * and then set tracer_enabled = 1. We want to make sure 386 * that another CPU does not see the tracer_enabled = 1 387 * and the wakeup_task with an older task, that might 388 * actually be the same as next. 389 */ 390 smp_rmb(); 391 392 if (next != wakeup_task) 393 return; 394 395 pc = preempt_count(); 396 397 /* disable local data, not wakeup_cpu data */ 398 cpu = raw_smp_processor_id(); 399 disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled); 400 if (likely(disabled != 1)) 401 goto out; 402 403 local_irq_save(flags); 404 arch_spin_lock(&wakeup_lock); 405 406 /* We could race with grabbing wakeup_lock */ 407 if (unlikely(!tracer_enabled || next != wakeup_task)) 408 goto out_unlock; 409 410 /* The task we are waiting for is waking up */ 411 data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu); 412 413 __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc); 414 tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc); 415 416 T0 = data->preempt_timestamp; 417 T1 = ftrace_now(cpu); 418 delta = T1-T0; 419 420 if (!report_latency(delta)) 421 goto out_unlock; 422 423 if (likely(!is_tracing_stopped())) { 424 tracing_max_latency = delta; 425 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu); 426 } 427 428 out_unlock: 429 __wakeup_reset(wakeup_trace); 430 arch_spin_unlock(&wakeup_lock); 431 local_irq_restore(flags); 432 out: 433 atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled); 434 } 435 436 static void __wakeup_reset(struct trace_array *tr) 437 { 438 wakeup_cpu = -1; 439 wakeup_prio = -1; 440 441 if (wakeup_task) 442 put_task_struct(wakeup_task); 443 444 wakeup_task = NULL; 445 } 446 447 static void wakeup_reset(struct trace_array *tr) 448 { 449 unsigned long flags; 450 451 tracing_reset_online_cpus(&tr->trace_buffer); 452 453 local_irq_save(flags); 454 arch_spin_lock(&wakeup_lock); 455 __wakeup_reset(tr); 456 arch_spin_unlock(&wakeup_lock); 457 local_irq_restore(flags); 458 } 459 460 static void 461 probe_wakeup(void *ignore, struct task_struct *p, int success) 462 { 463 struct trace_array_cpu *data; 464 int cpu = smp_processor_id(); 465 unsigned long flags; 466 long disabled; 467 int pc; 468 469 if (likely(!tracer_enabled)) 470 return; 471 472 tracing_record_cmdline(p); 473 tracing_record_cmdline(current); 474 475 if ((wakeup_rt && !rt_task(p)) || 476 p->prio >= wakeup_prio || 477 p->prio >= current->prio) 478 return; 479 480 pc = preempt_count(); 481 disabled = atomic_inc_return(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled); 482 if (unlikely(disabled != 1)) 483 goto out; 484 485 /* interrupts should be off from try_to_wake_up */ 486 arch_spin_lock(&wakeup_lock); 487 488 /* check for races. */ 489 if (!tracer_enabled || p->prio >= wakeup_prio) 490 goto out_locked; 491 492 /* reset the trace */ 493 __wakeup_reset(wakeup_trace); 494 495 wakeup_cpu = task_cpu(p); 496 wakeup_current_cpu = wakeup_cpu; 497 wakeup_prio = p->prio; 498 499 wakeup_task = p; 500 get_task_struct(wakeup_task); 501 502 local_save_flags(flags); 503 504 data = per_cpu_ptr(wakeup_trace->trace_buffer.data, wakeup_cpu); 505 data->preempt_timestamp = ftrace_now(cpu); 506 tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc); 507 508 /* 509 * We must be careful in using CALLER_ADDR2. But since wake_up 510 * is not called by an assembly function (where as schedule is) 511 * it should be safe to use it here. 512 */ 513 __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc); 514 515 out_locked: 516 arch_spin_unlock(&wakeup_lock); 517 out: 518 atomic_dec(&per_cpu_ptr(wakeup_trace->trace_buffer.data, cpu)->disabled); 519 } 520 521 static void start_wakeup_tracer(struct trace_array *tr) 522 { 523 int ret; 524 525 ret = register_trace_sched_wakeup(probe_wakeup, NULL); 526 if (ret) { 527 pr_info("wakeup trace: Couldn't activate tracepoint" 528 " probe to kernel_sched_wakeup\n"); 529 return; 530 } 531 532 ret = register_trace_sched_wakeup_new(probe_wakeup, NULL); 533 if (ret) { 534 pr_info("wakeup trace: Couldn't activate tracepoint" 535 " probe to kernel_sched_wakeup_new\n"); 536 goto fail_deprobe; 537 } 538 539 ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL); 540 if (ret) { 541 pr_info("sched trace: Couldn't activate tracepoint" 542 " probe to kernel_sched_switch\n"); 543 goto fail_deprobe_wake_new; 544 } 545 546 ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL); 547 if (ret) { 548 pr_info("wakeup trace: Couldn't activate tracepoint" 549 " probe to kernel_sched_migrate_task\n"); 550 return; 551 } 552 553 wakeup_reset(tr); 554 555 /* 556 * Don't let the tracer_enabled = 1 show up before 557 * the wakeup_task is reset. This may be overkill since 558 * wakeup_reset does a spin_unlock after setting the 559 * wakeup_task to NULL, but I want to be safe. 560 * This is a slow path anyway. 561 */ 562 smp_wmb(); 563 564 if (start_func_tracer(is_graph())) 565 printk(KERN_ERR "failed to start wakeup tracer\n"); 566 567 return; 568 fail_deprobe_wake_new: 569 unregister_trace_sched_wakeup_new(probe_wakeup, NULL); 570 fail_deprobe: 571 unregister_trace_sched_wakeup(probe_wakeup, NULL); 572 } 573 574 static void stop_wakeup_tracer(struct trace_array *tr) 575 { 576 tracer_enabled = 0; 577 stop_func_tracer(is_graph()); 578 unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL); 579 unregister_trace_sched_wakeup_new(probe_wakeup, NULL); 580 unregister_trace_sched_wakeup(probe_wakeup, NULL); 581 unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL); 582 } 583 584 static int __wakeup_tracer_init(struct trace_array *tr) 585 { 586 save_flags = trace_flags; 587 588 /* non overwrite screws up the latency tracers */ 589 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, 1); 590 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, 1); 591 592 tracing_max_latency = 0; 593 wakeup_trace = tr; 594 start_wakeup_tracer(tr); 595 return 0; 596 } 597 598 static int wakeup_tracer_init(struct trace_array *tr) 599 { 600 wakeup_rt = 0; 601 return __wakeup_tracer_init(tr); 602 } 603 604 static int wakeup_rt_tracer_init(struct trace_array *tr) 605 { 606 wakeup_rt = 1; 607 return __wakeup_tracer_init(tr); 608 } 609 610 static void wakeup_tracer_reset(struct trace_array *tr) 611 { 612 int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT; 613 int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE; 614 615 stop_wakeup_tracer(tr); 616 /* make sure we put back any tasks we are tracing */ 617 wakeup_reset(tr); 618 619 set_tracer_flag(tr, TRACE_ITER_LATENCY_FMT, lat_flag); 620 set_tracer_flag(tr, TRACE_ITER_OVERWRITE, overwrite_flag); 621 } 622 623 static void wakeup_tracer_start(struct trace_array *tr) 624 { 625 wakeup_reset(tr); 626 tracer_enabled = 1; 627 } 628 629 static void wakeup_tracer_stop(struct trace_array *tr) 630 { 631 tracer_enabled = 0; 632 } 633 634 static struct tracer wakeup_tracer __read_mostly = 635 { 636 .name = "wakeup", 637 .init = wakeup_tracer_init, 638 .reset = wakeup_tracer_reset, 639 .start = wakeup_tracer_start, 640 .stop = wakeup_tracer_stop, 641 .print_max = true, 642 .print_header = wakeup_print_header, 643 .print_line = wakeup_print_line, 644 .flags = &tracer_flags, 645 .set_flag = wakeup_set_flag, 646 .flag_changed = wakeup_flag_changed, 647 #ifdef CONFIG_FTRACE_SELFTEST 648 .selftest = trace_selftest_startup_wakeup, 649 #endif 650 .open = wakeup_trace_open, 651 .close = wakeup_trace_close, 652 .use_max_tr = true, 653 }; 654 655 static struct tracer wakeup_rt_tracer __read_mostly = 656 { 657 .name = "wakeup_rt", 658 .init = wakeup_rt_tracer_init, 659 .reset = wakeup_tracer_reset, 660 .start = wakeup_tracer_start, 661 .stop = wakeup_tracer_stop, 662 .wait_pipe = poll_wait_pipe, 663 .print_max = true, 664 .print_header = wakeup_print_header, 665 .print_line = wakeup_print_line, 666 .flags = &tracer_flags, 667 .set_flag = wakeup_set_flag, 668 .flag_changed = wakeup_flag_changed, 669 #ifdef CONFIG_FTRACE_SELFTEST 670 .selftest = trace_selftest_startup_wakeup, 671 #endif 672 .open = wakeup_trace_open, 673 .close = wakeup_trace_close, 674 .use_max_tr = true, 675 }; 676 677 __init static int init_wakeup_tracer(void) 678 { 679 int ret; 680 681 ret = register_tracer(&wakeup_tracer); 682 if (ret) 683 return ret; 684 685 ret = register_tracer(&wakeup_rt_tracer); 686 if (ret) 687 return ret; 688 689 return 0; 690 } 691 core_initcall(init_wakeup_tracer); 692