1 /* 2 * linux/fs/proc/array.c 3 * 4 * Copyright (C) 1992 by Linus Torvalds 5 * based on ideas by Darren Senn 6 * 7 * Fixes: 8 * Michael. K. Johnson: stat,statm extensions. 9 * <johnsonm@stolaf.edu> 10 * 11 * Pauline Middelink : Made cmdline,envline only break at '\0's, to 12 * make sure SET_PROCTITLE works. Also removed 13 * bad '!' which forced address recalculation for 14 * EVERY character on the current page. 15 * <middelin@polyware.iaf.nl> 16 * 17 * Danny ter Haar : added cpuinfo 18 * <dth@cistron.nl> 19 * 20 * Alessandro Rubini : profile extension. 21 * <rubini@ipvvis.unipv.it> 22 * 23 * Jeff Tranter : added BogoMips field to cpuinfo 24 * <Jeff_Tranter@Mitel.COM> 25 * 26 * Bruno Haible : remove 4K limit for the maps file 27 * <haible@ma2s2.mathematik.uni-karlsruhe.de> 28 * 29 * Yves Arrouye : remove removal of trailing spaces in get_array. 30 * <Yves.Arrouye@marin.fdn.fr> 31 * 32 * Jerome Forissier : added per-CPU time information to /proc/stat 33 * and /proc/<pid>/cpu extension 34 * <forissier@isia.cma.fr> 35 * - Incorporation and non-SMP safe operation 36 * of forissier patch in 2.1.78 by 37 * Hans Marcus <crowbar@concepts.nl> 38 * 39 * aeb@cwi.nl : /proc/partitions 40 * 41 * 42 * Alan Cox : security fixes. 43 * <alan@lxorguk.ukuu.org.uk> 44 * 45 * Al Viro : safe handling of mm_struct 46 * 47 * Gerhard Wichert : added BIGMEM support 48 * Siemens AG <Gerhard.Wichert@pdb.siemens.de> 49 * 50 * Al Viro & Jeff Garzik : moved most of the thing into base.c and 51 * : proc_misc.c. The rest may eventually go into 52 * : base.c too. 53 */ 54 55 #include <linux/types.h> 56 #include <linux/errno.h> 57 #include <linux/time.h> 58 #include <linux/kernel.h> 59 #include <linux/kernel_stat.h> 60 #include <linux/tty.h> 61 #include <linux/string.h> 62 #include <linux/mman.h> 63 #include <linux/proc_fs.h> 64 #include <linux/ioport.h> 65 #include <linux/uaccess.h> 66 #include <linux/io.h> 67 #include <linux/mm.h> 68 #include <linux/hugetlb.h> 69 #include <linux/pagemap.h> 70 #include <linux/swap.h> 71 #include <linux/smp.h> 72 #include <linux/signal.h> 73 #include <linux/highmem.h> 74 #include <linux/file.h> 75 #include <linux/fdtable.h> 76 #include <linux/times.h> 77 #include <linux/cpuset.h> 78 #include <linux/rcupdate.h> 79 #include <linux/delayacct.h> 80 #include <linux/seq_file.h> 81 #include <linux/pid_namespace.h> 82 #include <linux/ptrace.h> 83 #include <linux/tracehook.h> 84 #include <linux/string_helpers.h> 85 #include <linux/user_namespace.h> 86 87 #include <asm/pgtable.h> 88 #include <asm/processor.h> 89 #include "internal.h" 90 91 static inline void task_name(struct seq_file *m, struct task_struct *p) 92 { 93 char *buf; 94 size_t size; 95 char tcomm[sizeof(p->comm)]; 96 int ret; 97 98 get_task_comm(tcomm, p); 99 100 seq_puts(m, "Name:\t"); 101 102 size = seq_get_buf(m, &buf); 103 ret = string_escape_str(tcomm, buf, size, ESCAPE_SPACE | ESCAPE_SPECIAL, "\n\\"); 104 seq_commit(m, ret < size ? ret : -1); 105 106 seq_putc(m, '\n'); 107 } 108 109 /* 110 * The task state array is a strange "bitmap" of 111 * reasons to sleep. Thus "running" is zero, and 112 * you can test for combinations of others with 113 * simple bit tests. 114 */ 115 static const char * const task_state_array[] = { 116 "R (running)", /* 0 */ 117 "S (sleeping)", /* 1 */ 118 "D (disk sleep)", /* 2 */ 119 "T (stopped)", /* 4 */ 120 "t (tracing stop)", /* 8 */ 121 "X (dead)", /* 16 */ 122 "Z (zombie)", /* 32 */ 123 }; 124 125 static inline const char *get_task_state(struct task_struct *tsk) 126 { 127 unsigned int state = (tsk->state | tsk->exit_state) & TASK_REPORT; 128 129 /* 130 * Parked tasks do not run; they sit in __kthread_parkme(). 131 * Without this check, we would report them as running, which is 132 * clearly wrong, so we report them as sleeping instead. 133 */ 134 if (tsk->state == TASK_PARKED) 135 state = TASK_INTERRUPTIBLE; 136 137 BUILD_BUG_ON(1 + ilog2(TASK_REPORT) != ARRAY_SIZE(task_state_array)-1); 138 139 return task_state_array[fls(state)]; 140 } 141 142 static inline void task_state(struct seq_file *m, struct pid_namespace *ns, 143 struct pid *pid, struct task_struct *p) 144 { 145 struct user_namespace *user_ns = seq_user_ns(m); 146 struct group_info *group_info; 147 int g; 148 struct task_struct *tracer; 149 const struct cred *cred; 150 pid_t ppid, tpid = 0, tgid, ngid; 151 unsigned int max_fds = 0; 152 153 rcu_read_lock(); 154 ppid = pid_alive(p) ? 155 task_tgid_nr_ns(rcu_dereference(p->real_parent), ns) : 0; 156 157 tracer = ptrace_parent(p); 158 if (tracer) 159 tpid = task_pid_nr_ns(tracer, ns); 160 161 tgid = task_tgid_nr_ns(p, ns); 162 ngid = task_numa_group_id(p); 163 cred = get_task_cred(p); 164 165 task_lock(p); 166 if (p->files) 167 max_fds = files_fdtable(p->files)->max_fds; 168 task_unlock(p); 169 rcu_read_unlock(); 170 171 seq_printf(m, 172 "State:\t%s\n" 173 "Tgid:\t%d\n" 174 "Ngid:\t%d\n" 175 "Pid:\t%d\n" 176 "PPid:\t%d\n" 177 "TracerPid:\t%d\n" 178 "Uid:\t%d\t%d\t%d\t%d\n" 179 "Gid:\t%d\t%d\t%d\t%d\n" 180 "FDSize:\t%d\nGroups:\t", 181 get_task_state(p), 182 tgid, ngid, pid_nr_ns(pid, ns), ppid, tpid, 183 from_kuid_munged(user_ns, cred->uid), 184 from_kuid_munged(user_ns, cred->euid), 185 from_kuid_munged(user_ns, cred->suid), 186 from_kuid_munged(user_ns, cred->fsuid), 187 from_kgid_munged(user_ns, cred->gid), 188 from_kgid_munged(user_ns, cred->egid), 189 from_kgid_munged(user_ns, cred->sgid), 190 from_kgid_munged(user_ns, cred->fsgid), 191 max_fds); 192 193 group_info = cred->group_info; 194 for (g = 0; g < group_info->ngroups; g++) 195 seq_printf(m, "%d ", 196 from_kgid_munged(user_ns, GROUP_AT(group_info, g))); 197 put_cred(cred); 198 199 #ifdef CONFIG_PID_NS 200 seq_puts(m, "\nNStgid:"); 201 for (g = ns->level; g <= pid->level; g++) 202 seq_printf(m, "\t%d", 203 task_tgid_nr_ns(p, pid->numbers[g].ns)); 204 seq_puts(m, "\nNSpid:"); 205 for (g = ns->level; g <= pid->level; g++) 206 seq_printf(m, "\t%d", 207 task_pid_nr_ns(p, pid->numbers[g].ns)); 208 seq_puts(m, "\nNSpgid:"); 209 for (g = ns->level; g <= pid->level; g++) 210 seq_printf(m, "\t%d", 211 task_pgrp_nr_ns(p, pid->numbers[g].ns)); 212 seq_puts(m, "\nNSsid:"); 213 for (g = ns->level; g <= pid->level; g++) 214 seq_printf(m, "\t%d", 215 task_session_nr_ns(p, pid->numbers[g].ns)); 216 #endif 217 seq_putc(m, '\n'); 218 } 219 220 void render_sigset_t(struct seq_file *m, const char *header, 221 sigset_t *set) 222 { 223 int i; 224 225 seq_puts(m, header); 226 227 i = _NSIG; 228 do { 229 int x = 0; 230 231 i -= 4; 232 if (sigismember(set, i+1)) x |= 1; 233 if (sigismember(set, i+2)) x |= 2; 234 if (sigismember(set, i+3)) x |= 4; 235 if (sigismember(set, i+4)) x |= 8; 236 seq_printf(m, "%x", x); 237 } while (i >= 4); 238 239 seq_putc(m, '\n'); 240 } 241 242 static void collect_sigign_sigcatch(struct task_struct *p, sigset_t *ign, 243 sigset_t *catch) 244 { 245 struct k_sigaction *k; 246 int i; 247 248 k = p->sighand->action; 249 for (i = 1; i <= _NSIG; ++i, ++k) { 250 if (k->sa.sa_handler == SIG_IGN) 251 sigaddset(ign, i); 252 else if (k->sa.sa_handler != SIG_DFL) 253 sigaddset(catch, i); 254 } 255 } 256 257 static inline void task_sig(struct seq_file *m, struct task_struct *p) 258 { 259 unsigned long flags; 260 sigset_t pending, shpending, blocked, ignored, caught; 261 int num_threads = 0; 262 unsigned long qsize = 0; 263 unsigned long qlim = 0; 264 265 sigemptyset(&pending); 266 sigemptyset(&shpending); 267 sigemptyset(&blocked); 268 sigemptyset(&ignored); 269 sigemptyset(&caught); 270 271 if (lock_task_sighand(p, &flags)) { 272 pending = p->pending.signal; 273 shpending = p->signal->shared_pending.signal; 274 blocked = p->blocked; 275 collect_sigign_sigcatch(p, &ignored, &caught); 276 num_threads = get_nr_threads(p); 277 rcu_read_lock(); /* FIXME: is this correct? */ 278 qsize = atomic_read(&__task_cred(p)->user->sigpending); 279 rcu_read_unlock(); 280 qlim = task_rlimit(p, RLIMIT_SIGPENDING); 281 unlock_task_sighand(p, &flags); 282 } 283 284 seq_printf(m, "Threads:\t%d\n", num_threads); 285 seq_printf(m, "SigQ:\t%lu/%lu\n", qsize, qlim); 286 287 /* render them all */ 288 render_sigset_t(m, "SigPnd:\t", &pending); 289 render_sigset_t(m, "ShdPnd:\t", &shpending); 290 render_sigset_t(m, "SigBlk:\t", &blocked); 291 render_sigset_t(m, "SigIgn:\t", &ignored); 292 render_sigset_t(m, "SigCgt:\t", &caught); 293 } 294 295 static void render_cap_t(struct seq_file *m, const char *header, 296 kernel_cap_t *a) 297 { 298 unsigned __capi; 299 300 seq_puts(m, header); 301 CAP_FOR_EACH_U32(__capi) { 302 seq_printf(m, "%08x", 303 a->cap[CAP_LAST_U32 - __capi]); 304 } 305 seq_putc(m, '\n'); 306 } 307 308 static inline void task_cap(struct seq_file *m, struct task_struct *p) 309 { 310 const struct cred *cred; 311 kernel_cap_t cap_inheritable, cap_permitted, cap_effective, 312 cap_bset, cap_ambient; 313 314 rcu_read_lock(); 315 cred = __task_cred(p); 316 cap_inheritable = cred->cap_inheritable; 317 cap_permitted = cred->cap_permitted; 318 cap_effective = cred->cap_effective; 319 cap_bset = cred->cap_bset; 320 cap_ambient = cred->cap_ambient; 321 rcu_read_unlock(); 322 323 render_cap_t(m, "CapInh:\t", &cap_inheritable); 324 render_cap_t(m, "CapPrm:\t", &cap_permitted); 325 render_cap_t(m, "CapEff:\t", &cap_effective); 326 render_cap_t(m, "CapBnd:\t", &cap_bset); 327 render_cap_t(m, "CapAmb:\t", &cap_ambient); 328 } 329 330 static inline void task_seccomp(struct seq_file *m, struct task_struct *p) 331 { 332 #ifdef CONFIG_SECCOMP 333 seq_printf(m, "Seccomp:\t%d\n", p->seccomp.mode); 334 #endif 335 } 336 337 static inline void task_context_switch_counts(struct seq_file *m, 338 struct task_struct *p) 339 { 340 seq_printf(m, "voluntary_ctxt_switches:\t%lu\n" 341 "nonvoluntary_ctxt_switches:\t%lu\n", 342 p->nvcsw, 343 p->nivcsw); 344 } 345 346 static void task_cpus_allowed(struct seq_file *m, struct task_struct *task) 347 { 348 seq_printf(m, "Cpus_allowed:\t%*pb\n", 349 cpumask_pr_args(&task->cpus_allowed)); 350 seq_printf(m, "Cpus_allowed_list:\t%*pbl\n", 351 cpumask_pr_args(&task->cpus_allowed)); 352 } 353 354 int proc_pid_status(struct seq_file *m, struct pid_namespace *ns, 355 struct pid *pid, struct task_struct *task) 356 { 357 struct mm_struct *mm = get_task_mm(task); 358 359 task_name(m, task); 360 task_state(m, ns, pid, task); 361 362 if (mm) { 363 task_mem(m, mm); 364 mmput(mm); 365 } 366 task_sig(m, task); 367 task_cap(m, task); 368 task_seccomp(m, task); 369 task_cpus_allowed(m, task); 370 cpuset_task_status_allowed(m, task); 371 task_context_switch_counts(m, task); 372 return 0; 373 } 374 375 static int do_task_stat(struct seq_file *m, struct pid_namespace *ns, 376 struct pid *pid, struct task_struct *task, int whole) 377 { 378 unsigned long vsize, eip, esp, wchan = 0; 379 int priority, nice; 380 int tty_pgrp = -1, tty_nr = 0; 381 sigset_t sigign, sigcatch; 382 char state; 383 pid_t ppid = 0, pgid = -1, sid = -1; 384 int num_threads = 0; 385 int permitted; 386 struct mm_struct *mm; 387 unsigned long long start_time; 388 unsigned long cmin_flt = 0, cmaj_flt = 0; 389 unsigned long min_flt = 0, maj_flt = 0; 390 cputime_t cutime, cstime, utime, stime; 391 cputime_t cgtime, gtime; 392 unsigned long rsslim = 0; 393 char tcomm[sizeof(task->comm)]; 394 unsigned long flags; 395 396 state = *get_task_state(task); 397 vsize = eip = esp = 0; 398 permitted = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS | PTRACE_MODE_NOAUDIT); 399 mm = get_task_mm(task); 400 if (mm) { 401 vsize = task_vsize(mm); 402 if (permitted) { 403 eip = KSTK_EIP(task); 404 esp = KSTK_ESP(task); 405 } 406 } 407 408 get_task_comm(tcomm, task); 409 410 sigemptyset(&sigign); 411 sigemptyset(&sigcatch); 412 cutime = cstime = utime = stime = 0; 413 cgtime = gtime = 0; 414 415 if (lock_task_sighand(task, &flags)) { 416 struct signal_struct *sig = task->signal; 417 418 if (sig->tty) { 419 struct pid *pgrp = tty_get_pgrp(sig->tty); 420 tty_pgrp = pid_nr_ns(pgrp, ns); 421 put_pid(pgrp); 422 tty_nr = new_encode_dev(tty_devnum(sig->tty)); 423 } 424 425 num_threads = get_nr_threads(task); 426 collect_sigign_sigcatch(task, &sigign, &sigcatch); 427 428 cmin_flt = sig->cmin_flt; 429 cmaj_flt = sig->cmaj_flt; 430 cutime = sig->cutime; 431 cstime = sig->cstime; 432 cgtime = sig->cgtime; 433 rsslim = ACCESS_ONCE(sig->rlim[RLIMIT_RSS].rlim_cur); 434 435 /* add up live thread stats at the group level */ 436 if (whole) { 437 struct task_struct *t = task; 438 do { 439 min_flt += t->min_flt; 440 maj_flt += t->maj_flt; 441 gtime += task_gtime(t); 442 } while_each_thread(task, t); 443 444 min_flt += sig->min_flt; 445 maj_flt += sig->maj_flt; 446 thread_group_cputime_adjusted(task, &utime, &stime); 447 gtime += sig->gtime; 448 } 449 450 sid = task_session_nr_ns(task, ns); 451 ppid = task_tgid_nr_ns(task->real_parent, ns); 452 pgid = task_pgrp_nr_ns(task, ns); 453 454 unlock_task_sighand(task, &flags); 455 } 456 457 if (permitted && (!whole || num_threads < 2)) 458 wchan = get_wchan(task); 459 if (!whole) { 460 min_flt = task->min_flt; 461 maj_flt = task->maj_flt; 462 task_cputime_adjusted(task, &utime, &stime); 463 gtime = task_gtime(task); 464 } 465 466 /* scale priority and nice values from timeslices to -20..20 */ 467 /* to make it look like a "normal" Unix priority/nice value */ 468 priority = task_prio(task); 469 nice = task_nice(task); 470 471 /* convert nsec -> ticks */ 472 start_time = nsec_to_clock_t(task->real_start_time); 473 474 seq_printf(m, "%d (%s) %c", pid_nr_ns(pid, ns), tcomm, state); 475 seq_put_decimal_ll(m, ' ', ppid); 476 seq_put_decimal_ll(m, ' ', pgid); 477 seq_put_decimal_ll(m, ' ', sid); 478 seq_put_decimal_ll(m, ' ', tty_nr); 479 seq_put_decimal_ll(m, ' ', tty_pgrp); 480 seq_put_decimal_ull(m, ' ', task->flags); 481 seq_put_decimal_ull(m, ' ', min_flt); 482 seq_put_decimal_ull(m, ' ', cmin_flt); 483 seq_put_decimal_ull(m, ' ', maj_flt); 484 seq_put_decimal_ull(m, ' ', cmaj_flt); 485 seq_put_decimal_ull(m, ' ', cputime_to_clock_t(utime)); 486 seq_put_decimal_ull(m, ' ', cputime_to_clock_t(stime)); 487 seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cutime)); 488 seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cstime)); 489 seq_put_decimal_ll(m, ' ', priority); 490 seq_put_decimal_ll(m, ' ', nice); 491 seq_put_decimal_ll(m, ' ', num_threads); 492 seq_put_decimal_ull(m, ' ', 0); 493 seq_put_decimal_ull(m, ' ', start_time); 494 seq_put_decimal_ull(m, ' ', vsize); 495 seq_put_decimal_ull(m, ' ', mm ? get_mm_rss(mm) : 0); 496 seq_put_decimal_ull(m, ' ', rsslim); 497 seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->start_code : 1) : 0); 498 seq_put_decimal_ull(m, ' ', mm ? (permitted ? mm->end_code : 1) : 0); 499 seq_put_decimal_ull(m, ' ', (permitted && mm) ? mm->start_stack : 0); 500 seq_put_decimal_ull(m, ' ', esp); 501 seq_put_decimal_ull(m, ' ', eip); 502 /* The signal information here is obsolete. 503 * It must be decimal for Linux 2.0 compatibility. 504 * Use /proc/#/status for real-time signals. 505 */ 506 seq_put_decimal_ull(m, ' ', task->pending.signal.sig[0] & 0x7fffffffUL); 507 seq_put_decimal_ull(m, ' ', task->blocked.sig[0] & 0x7fffffffUL); 508 seq_put_decimal_ull(m, ' ', sigign.sig[0] & 0x7fffffffUL); 509 seq_put_decimal_ull(m, ' ', sigcatch.sig[0] & 0x7fffffffUL); 510 511 /* 512 * We used to output the absolute kernel address, but that's an 513 * information leak - so instead we show a 0/1 flag here, to signal 514 * to user-space whether there's a wchan field in /proc/PID/wchan. 515 * 516 * This works with older implementations of procps as well. 517 */ 518 if (wchan) 519 seq_puts(m, " 1"); 520 else 521 seq_puts(m, " 0"); 522 523 seq_put_decimal_ull(m, ' ', 0); 524 seq_put_decimal_ull(m, ' ', 0); 525 seq_put_decimal_ll(m, ' ', task->exit_signal); 526 seq_put_decimal_ll(m, ' ', task_cpu(task)); 527 seq_put_decimal_ull(m, ' ', task->rt_priority); 528 seq_put_decimal_ull(m, ' ', task->policy); 529 seq_put_decimal_ull(m, ' ', delayacct_blkio_ticks(task)); 530 seq_put_decimal_ull(m, ' ', cputime_to_clock_t(gtime)); 531 seq_put_decimal_ll(m, ' ', cputime_to_clock_t(cgtime)); 532 533 if (mm && permitted) { 534 seq_put_decimal_ull(m, ' ', mm->start_data); 535 seq_put_decimal_ull(m, ' ', mm->end_data); 536 seq_put_decimal_ull(m, ' ', mm->start_brk); 537 seq_put_decimal_ull(m, ' ', mm->arg_start); 538 seq_put_decimal_ull(m, ' ', mm->arg_end); 539 seq_put_decimal_ull(m, ' ', mm->env_start); 540 seq_put_decimal_ull(m, ' ', mm->env_end); 541 } else 542 seq_printf(m, " 0 0 0 0 0 0 0"); 543 544 if (permitted) 545 seq_put_decimal_ll(m, ' ', task->exit_code); 546 else 547 seq_put_decimal_ll(m, ' ', 0); 548 549 seq_putc(m, '\n'); 550 if (mm) 551 mmput(mm); 552 return 0; 553 } 554 555 int proc_tid_stat(struct seq_file *m, struct pid_namespace *ns, 556 struct pid *pid, struct task_struct *task) 557 { 558 return do_task_stat(m, ns, pid, task, 0); 559 } 560 561 int proc_tgid_stat(struct seq_file *m, struct pid_namespace *ns, 562 struct pid *pid, struct task_struct *task) 563 { 564 return do_task_stat(m, ns, pid, task, 1); 565 } 566 567 int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns, 568 struct pid *pid, struct task_struct *task) 569 { 570 unsigned long size = 0, resident = 0, shared = 0, text = 0, data = 0; 571 struct mm_struct *mm = get_task_mm(task); 572 573 if (mm) { 574 size = task_statm(mm, &shared, &text, &data, &resident); 575 mmput(mm); 576 } 577 /* 578 * For quick read, open code by putting numbers directly 579 * expected format is 580 * seq_printf(m, "%lu %lu %lu %lu 0 %lu 0\n", 581 * size, resident, shared, text, data); 582 */ 583 seq_put_decimal_ull(m, 0, size); 584 seq_put_decimal_ull(m, ' ', resident); 585 seq_put_decimal_ull(m, ' ', shared); 586 seq_put_decimal_ull(m, ' ', text); 587 seq_put_decimal_ull(m, ' ', 0); 588 seq_put_decimal_ull(m, ' ', data); 589 seq_put_decimal_ull(m, ' ', 0); 590 seq_putc(m, '\n'); 591 592 return 0; 593 } 594 595 #ifdef CONFIG_PROC_CHILDREN 596 static struct pid * 597 get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos) 598 { 599 struct task_struct *start, *task; 600 struct pid *pid = NULL; 601 602 read_lock(&tasklist_lock); 603 604 start = pid_task(proc_pid(inode), PIDTYPE_PID); 605 if (!start) 606 goto out; 607 608 /* 609 * Lets try to continue searching first, this gives 610 * us significant speedup on children-rich processes. 611 */ 612 if (pid_prev) { 613 task = pid_task(pid_prev, PIDTYPE_PID); 614 if (task && task->real_parent == start && 615 !(list_empty(&task->sibling))) { 616 if (list_is_last(&task->sibling, &start->children)) 617 goto out; 618 task = list_first_entry(&task->sibling, 619 struct task_struct, sibling); 620 pid = get_pid(task_pid(task)); 621 goto out; 622 } 623 } 624 625 /* 626 * Slow search case. 627 * 628 * We might miss some children here if children 629 * are exited while we were not holding the lock, 630 * but it was never promised to be accurate that 631 * much. 632 * 633 * "Just suppose that the parent sleeps, but N children 634 * exit after we printed their tids. Now the slow paths 635 * skips N extra children, we miss N tasks." (c) 636 * 637 * So one need to stop or freeze the leader and all 638 * its children to get a precise result. 639 */ 640 list_for_each_entry(task, &start->children, sibling) { 641 if (pos-- == 0) { 642 pid = get_pid(task_pid(task)); 643 break; 644 } 645 } 646 647 out: 648 read_unlock(&tasklist_lock); 649 return pid; 650 } 651 652 static int children_seq_show(struct seq_file *seq, void *v) 653 { 654 struct inode *inode = seq->private; 655 pid_t pid; 656 657 pid = pid_nr_ns(v, inode->i_sb->s_fs_info); 658 seq_printf(seq, "%d ", pid); 659 660 return 0; 661 } 662 663 static void *children_seq_start(struct seq_file *seq, loff_t *pos) 664 { 665 return get_children_pid(seq->private, NULL, *pos); 666 } 667 668 static void *children_seq_next(struct seq_file *seq, void *v, loff_t *pos) 669 { 670 struct pid *pid; 671 672 pid = get_children_pid(seq->private, v, *pos + 1); 673 put_pid(v); 674 675 ++*pos; 676 return pid; 677 } 678 679 static void children_seq_stop(struct seq_file *seq, void *v) 680 { 681 put_pid(v); 682 } 683 684 static const struct seq_operations children_seq_ops = { 685 .start = children_seq_start, 686 .next = children_seq_next, 687 .stop = children_seq_stop, 688 .show = children_seq_show, 689 }; 690 691 static int children_seq_open(struct inode *inode, struct file *file) 692 { 693 struct seq_file *m; 694 int ret; 695 696 ret = seq_open(file, &children_seq_ops); 697 if (ret) 698 return ret; 699 700 m = file->private_data; 701 m->private = inode; 702 703 return ret; 704 } 705 706 int children_seq_release(struct inode *inode, struct file *file) 707 { 708 seq_release(inode, file); 709 return 0; 710 } 711 712 const struct file_operations proc_tid_children_operations = { 713 .open = children_seq_open, 714 .read = seq_read, 715 .llseek = seq_lseek, 716 .release = children_seq_release, 717 }; 718 #endif /* CONFIG_PROC_CHILDREN */ 719