1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * linux/mm/oom_kill.c 4 * 5 * Copyright (C) 1998,2000 Rik van Riel 6 * Thanks go out to Claus Fischer for some serious inspiration and 7 * for goading me into coding this file... 8 * Copyright (C) 2010 Google, Inc. 9 * Rewritten by David Rientjes 10 * 11 * The routines in this file are used to kill a process when 12 * we're seriously out of memory. This gets called from __alloc_pages() 13 * in mm/page_alloc.c when we really run out of memory. 14 * 15 * Since we won't call these routines often (on a well-configured 16 * machine) this file will double as a 'coding guide' and a signpost 17 * for newbie kernel hackers. It features several pointers to major 18 * kernel subsystems and hints as to where to find out what things do. 19 */ 20 21 #include <linux/oom.h> 22 #include <linux/mm.h> 23 #include <linux/err.h> 24 #include <linux/gfp.h> 25 #include <linux/sched.h> 26 #include <linux/sched/mm.h> 27 #include <linux/sched/coredump.h> 28 #include <linux/sched/task.h> 29 #include <linux/sched/debug.h> 30 #include <linux/swap.h> 31 #include <linux/syscalls.h> 32 #include <linux/timex.h> 33 #include <linux/jiffies.h> 34 #include <linux/cpuset.h> 35 #include <linux/export.h> 36 #include <linux/notifier.h> 37 #include <linux/memcontrol.h> 38 #include <linux/mempolicy.h> 39 #include <linux/security.h> 40 #include <linux/ptrace.h> 41 #include <linux/freezer.h> 42 #include <linux/ftrace.h> 43 #include <linux/ratelimit.h> 44 #include <linux/kthread.h> 45 #include <linux/init.h> 46 #include <linux/mmu_notifier.h> 47 48 #include <asm/tlb.h> 49 #include "internal.h" 50 #include "slab.h" 51 52 #define CREATE_TRACE_POINTS 53 #include <trace/events/oom.h> 54 55 static int sysctl_panic_on_oom; 56 static int sysctl_oom_kill_allocating_task; 57 static int sysctl_oom_dump_tasks = 1; 58 59 /* 60 * Serializes oom killer invocations (out_of_memory()) from all contexts to 61 * prevent from over eager oom killing (e.g. when the oom killer is invoked 62 * from different domains). 63 * 64 * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled 65 * and mark_oom_victim 66 */ 67 DEFINE_MUTEX(oom_lock); 68 /* Serializes oom_score_adj and oom_score_adj_min updates */ 69 DEFINE_MUTEX(oom_adj_mutex); 70 71 static inline bool is_memcg_oom(struct oom_control *oc) 72 { 73 return oc->memcg != NULL; 74 } 75 76 #ifdef CONFIG_NUMA 77 /** 78 * oom_cpuset_eligible() - check task eligibility for kill 79 * @start: task struct of which task to consider 80 * @oc: pointer to struct oom_control 81 * 82 * Task eligibility is determined by whether or not a candidate task, @tsk, 83 * shares the same mempolicy nodes as current if it is bound by such a policy 84 * and whether or not it has the same set of allowed cpuset nodes. 85 * 86 * This function is assuming oom-killer context and 'current' has triggered 87 * the oom-killer. 88 */ 89 static bool oom_cpuset_eligible(struct task_struct *start, 90 struct oom_control *oc) 91 { 92 struct task_struct *tsk; 93 bool ret = false; 94 const nodemask_t *mask = oc->nodemask; 95 96 rcu_read_lock(); 97 for_each_thread(start, tsk) { 98 if (mask) { 99 /* 100 * If this is a mempolicy constrained oom, tsk's 101 * cpuset is irrelevant. Only return true if its 102 * mempolicy intersects current, otherwise it may be 103 * needlessly killed. 104 */ 105 ret = mempolicy_in_oom_domain(tsk, mask); 106 } else { 107 /* 108 * This is not a mempolicy constrained oom, so only 109 * check the mems of tsk's cpuset. 110 */ 111 ret = cpuset_mems_allowed_intersects(current, tsk); 112 } 113 if (ret) 114 break; 115 } 116 rcu_read_unlock(); 117 118 return ret; 119 } 120 #else 121 static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc) 122 { 123 return true; 124 } 125 #endif /* CONFIG_NUMA */ 126 127 /* 128 * The process p may have detached its own ->mm while exiting or through 129 * kthread_use_mm(), but one or more of its subthreads may still have a valid 130 * pointer. Return p, or any of its subthreads with a valid ->mm, with 131 * task_lock() held. 132 */ 133 struct task_struct *find_lock_task_mm(struct task_struct *p) 134 { 135 struct task_struct *t; 136 137 rcu_read_lock(); 138 139 for_each_thread(p, t) { 140 task_lock(t); 141 if (likely(t->mm)) 142 goto found; 143 task_unlock(t); 144 } 145 t = NULL; 146 found: 147 rcu_read_unlock(); 148 149 return t; 150 } 151 152 /* 153 * order == -1 means the oom kill is required by sysrq, otherwise only 154 * for display purposes. 155 */ 156 static inline bool is_sysrq_oom(struct oom_control *oc) 157 { 158 return oc->order == -1; 159 } 160 161 /* return true if the task is not adequate as candidate victim task. */ 162 static bool oom_unkillable_task(struct task_struct *p) 163 { 164 if (is_global_init(p)) 165 return true; 166 if (p->flags & PF_KTHREAD) 167 return true; 168 return false; 169 } 170 171 /* 172 * Check whether unreclaimable slab amount is greater than 173 * all user memory(LRU pages). 174 * dump_unreclaimable_slab() could help in the case that 175 * oom due to too much unreclaimable slab used by kernel. 176 */ 177 static bool should_dump_unreclaim_slab(void) 178 { 179 unsigned long nr_lru; 180 181 nr_lru = global_node_page_state(NR_ACTIVE_ANON) + 182 global_node_page_state(NR_INACTIVE_ANON) + 183 global_node_page_state(NR_ACTIVE_FILE) + 184 global_node_page_state(NR_INACTIVE_FILE) + 185 global_node_page_state(NR_ISOLATED_ANON) + 186 global_node_page_state(NR_ISOLATED_FILE) + 187 global_node_page_state(NR_UNEVICTABLE); 188 189 return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru); 190 } 191 192 /** 193 * oom_badness - heuristic function to determine which candidate task to kill 194 * @p: task struct of which task we should calculate 195 * @totalpages: total present RAM allowed for page allocation 196 * 197 * The heuristic for determining which task to kill is made to be as simple and 198 * predictable as possible. The goal is to return the highest value for the 199 * task consuming the most memory to avoid subsequent oom failures. 200 */ 201 long oom_badness(struct task_struct *p, unsigned long totalpages) 202 { 203 long points; 204 long adj; 205 206 if (oom_unkillable_task(p)) 207 return LONG_MIN; 208 209 p = find_lock_task_mm(p); 210 if (!p) 211 return LONG_MIN; 212 213 /* 214 * Do not even consider tasks which are explicitly marked oom 215 * unkillable or have been already oom reaped or the are in 216 * the middle of vfork 217 */ 218 adj = (long)p->signal->oom_score_adj; 219 if (adj == OOM_SCORE_ADJ_MIN || 220 test_bit(MMF_OOM_SKIP, &p->mm->flags) || 221 in_vfork(p)) { 222 task_unlock(p); 223 return LONG_MIN; 224 } 225 226 /* 227 * The baseline for the badness score is the proportion of RAM that each 228 * task's rss, pagetable and swap space use. 229 */ 230 points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) + 231 mm_pgtables_bytes(p->mm) / PAGE_SIZE; 232 task_unlock(p); 233 234 /* Normalize to oom_score_adj units */ 235 adj *= totalpages / 1000; 236 points += adj; 237 238 return points; 239 } 240 241 static const char * const oom_constraint_text[] = { 242 [CONSTRAINT_NONE] = "CONSTRAINT_NONE", 243 [CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET", 244 [CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY", 245 [CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG", 246 }; 247 248 /* 249 * Determine the type of allocation constraint. 250 */ 251 static enum oom_constraint constrained_alloc(struct oom_control *oc) 252 { 253 struct zone *zone; 254 struct zoneref *z; 255 enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask); 256 bool cpuset_limited = false; 257 int nid; 258 259 if (is_memcg_oom(oc)) { 260 oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1; 261 return CONSTRAINT_MEMCG; 262 } 263 264 /* Default to all available memory */ 265 oc->totalpages = totalram_pages() + total_swap_pages; 266 267 if (!IS_ENABLED(CONFIG_NUMA)) 268 return CONSTRAINT_NONE; 269 270 if (!oc->zonelist) 271 return CONSTRAINT_NONE; 272 /* 273 * Reach here only when __GFP_NOFAIL is used. So, we should avoid 274 * to kill current.We have to random task kill in this case. 275 * Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now. 276 */ 277 if (oc->gfp_mask & __GFP_THISNODE) 278 return CONSTRAINT_NONE; 279 280 /* 281 * This is not a __GFP_THISNODE allocation, so a truncated nodemask in 282 * the page allocator means a mempolicy is in effect. Cpuset policy 283 * is enforced in get_page_from_freelist(). 284 */ 285 if (oc->nodemask && 286 !nodes_subset(node_states[N_MEMORY], *oc->nodemask)) { 287 oc->totalpages = total_swap_pages; 288 for_each_node_mask(nid, *oc->nodemask) 289 oc->totalpages += node_present_pages(nid); 290 return CONSTRAINT_MEMORY_POLICY; 291 } 292 293 /* Check this allocation failure is caused by cpuset's wall function */ 294 for_each_zone_zonelist_nodemask(zone, z, oc->zonelist, 295 highest_zoneidx, oc->nodemask) 296 if (!cpuset_zone_allowed(zone, oc->gfp_mask)) 297 cpuset_limited = true; 298 299 if (cpuset_limited) { 300 oc->totalpages = total_swap_pages; 301 for_each_node_mask(nid, cpuset_current_mems_allowed) 302 oc->totalpages += node_present_pages(nid); 303 return CONSTRAINT_CPUSET; 304 } 305 return CONSTRAINT_NONE; 306 } 307 308 static int oom_evaluate_task(struct task_struct *task, void *arg) 309 { 310 struct oom_control *oc = arg; 311 long points; 312 313 if (oom_unkillable_task(task)) 314 goto next; 315 316 /* p may not have freeable memory in nodemask */ 317 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc)) 318 goto next; 319 320 /* 321 * This task already has access to memory reserves and is being killed. 322 * Don't allow any other task to have access to the reserves unless 323 * the task has MMF_OOM_SKIP because chances that it would release 324 * any memory is quite low. 325 */ 326 if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) { 327 if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags)) 328 goto next; 329 goto abort; 330 } 331 332 /* 333 * If task is allocating a lot of memory and has been marked to be 334 * killed first if it triggers an oom, then select it. 335 */ 336 if (oom_task_origin(task)) { 337 points = LONG_MAX; 338 goto select; 339 } 340 341 points = oom_badness(task, oc->totalpages); 342 if (points == LONG_MIN || points < oc->chosen_points) 343 goto next; 344 345 select: 346 if (oc->chosen) 347 put_task_struct(oc->chosen); 348 get_task_struct(task); 349 oc->chosen = task; 350 oc->chosen_points = points; 351 next: 352 return 0; 353 abort: 354 if (oc->chosen) 355 put_task_struct(oc->chosen); 356 oc->chosen = (void *)-1UL; 357 return 1; 358 } 359 360 /* 361 * Simple selection loop. We choose the process with the highest number of 362 * 'points'. In case scan was aborted, oc->chosen is set to -1. 363 */ 364 static void select_bad_process(struct oom_control *oc) 365 { 366 oc->chosen_points = LONG_MIN; 367 368 if (is_memcg_oom(oc)) 369 mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc); 370 else { 371 struct task_struct *p; 372 373 rcu_read_lock(); 374 for_each_process(p) 375 if (oom_evaluate_task(p, oc)) 376 break; 377 rcu_read_unlock(); 378 } 379 } 380 381 static int dump_task(struct task_struct *p, void *arg) 382 { 383 struct oom_control *oc = arg; 384 struct task_struct *task; 385 386 if (oom_unkillable_task(p)) 387 return 0; 388 389 /* p may not have freeable memory in nodemask */ 390 if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc)) 391 return 0; 392 393 task = find_lock_task_mm(p); 394 if (!task) { 395 /* 396 * All of p's threads have already detached their mm's. There's 397 * no need to report them; they can't be oom killed anyway. 398 */ 399 return 0; 400 } 401 402 pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n", 403 task->pid, from_kuid(&init_user_ns, task_uid(task)), 404 task->tgid, task->mm->total_vm, get_mm_rss(task->mm), 405 mm_pgtables_bytes(task->mm), 406 get_mm_counter(task->mm, MM_SWAPENTS), 407 task->signal->oom_score_adj, task->comm); 408 task_unlock(task); 409 410 return 0; 411 } 412 413 /** 414 * dump_tasks - dump current memory state of all system tasks 415 * @oc: pointer to struct oom_control 416 * 417 * Dumps the current memory state of all eligible tasks. Tasks not in the same 418 * memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes 419 * are not shown. 420 * State information includes task's pid, uid, tgid, vm size, rss, 421 * pgtables_bytes, swapents, oom_score_adj value, and name. 422 */ 423 static void dump_tasks(struct oom_control *oc) 424 { 425 pr_info("Tasks state (memory values in pages):\n"); 426 pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n"); 427 428 if (is_memcg_oom(oc)) 429 mem_cgroup_scan_tasks(oc->memcg, dump_task, oc); 430 else { 431 struct task_struct *p; 432 433 rcu_read_lock(); 434 for_each_process(p) 435 dump_task(p, oc); 436 rcu_read_unlock(); 437 } 438 } 439 440 static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim) 441 { 442 /* one line summary of the oom killer context. */ 443 pr_info("oom-kill:constraint=%s,nodemask=%*pbl", 444 oom_constraint_text[oc->constraint], 445 nodemask_pr_args(oc->nodemask)); 446 cpuset_print_current_mems_allowed(); 447 mem_cgroup_print_oom_context(oc->memcg, victim); 448 pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid, 449 from_kuid(&init_user_ns, task_uid(victim))); 450 } 451 452 static void dump_header(struct oom_control *oc, struct task_struct *p) 453 { 454 pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n", 455 current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order, 456 current->signal->oom_score_adj); 457 if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order) 458 pr_warn("COMPACTION is disabled!!!\n"); 459 460 dump_stack(); 461 if (is_memcg_oom(oc)) 462 mem_cgroup_print_oom_meminfo(oc->memcg); 463 else { 464 show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask); 465 if (should_dump_unreclaim_slab()) 466 dump_unreclaimable_slab(); 467 } 468 if (sysctl_oom_dump_tasks) 469 dump_tasks(oc); 470 if (p) 471 dump_oom_summary(oc, p); 472 } 473 474 /* 475 * Number of OOM victims in flight 476 */ 477 static atomic_t oom_victims = ATOMIC_INIT(0); 478 static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait); 479 480 static bool oom_killer_disabled __read_mostly; 481 482 #define K(x) ((x) << (PAGE_SHIFT-10)) 483 484 /* 485 * task->mm can be NULL if the task is the exited group leader. So to 486 * determine whether the task is using a particular mm, we examine all the 487 * task's threads: if one of those is using this mm then this task was also 488 * using it. 489 */ 490 bool process_shares_mm(struct task_struct *p, struct mm_struct *mm) 491 { 492 struct task_struct *t; 493 494 for_each_thread(p, t) { 495 struct mm_struct *t_mm = READ_ONCE(t->mm); 496 if (t_mm) 497 return t_mm == mm; 498 } 499 return false; 500 } 501 502 #ifdef CONFIG_MMU 503 /* 504 * OOM Reaper kernel thread which tries to reap the memory used by the OOM 505 * victim (if that is possible) to help the OOM killer to move on. 506 */ 507 static struct task_struct *oom_reaper_th; 508 static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait); 509 static struct task_struct *oom_reaper_list; 510 static DEFINE_SPINLOCK(oom_reaper_lock); 511 512 bool __oom_reap_task_mm(struct mm_struct *mm) 513 { 514 struct vm_area_struct *vma; 515 bool ret = true; 516 517 /* 518 * Tell all users of get_user/copy_from_user etc... that the content 519 * is no longer stable. No barriers really needed because unmapping 520 * should imply barriers already and the reader would hit a page fault 521 * if it stumbled over a reaped memory. 522 */ 523 set_bit(MMF_UNSTABLE, &mm->flags); 524 525 for (vma = mm->mmap ; vma; vma = vma->vm_next) { 526 if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP)) 527 continue; 528 529 /* 530 * Only anonymous pages have a good chance to be dropped 531 * without additional steps which we cannot afford as we 532 * are OOM already. 533 * 534 * We do not even care about fs backed pages because all 535 * which are reclaimable have already been reclaimed and 536 * we do not want to block exit_mmap by keeping mm ref 537 * count elevated without a good reason. 538 */ 539 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) { 540 struct mmu_notifier_range range; 541 struct mmu_gather tlb; 542 543 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, 544 vma, mm, vma->vm_start, 545 vma->vm_end); 546 tlb_gather_mmu(&tlb, mm); 547 if (mmu_notifier_invalidate_range_start_nonblock(&range)) { 548 tlb_finish_mmu(&tlb); 549 ret = false; 550 continue; 551 } 552 unmap_page_range(&tlb, vma, range.start, range.end, NULL); 553 mmu_notifier_invalidate_range_end(&range); 554 tlb_finish_mmu(&tlb); 555 } 556 } 557 558 return ret; 559 } 560 561 /* 562 * Reaps the address space of the give task. 563 * 564 * Returns true on success and false if none or part of the address space 565 * has been reclaimed and the caller should retry later. 566 */ 567 static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) 568 { 569 bool ret = true; 570 571 if (!mmap_read_trylock(mm)) { 572 trace_skip_task_reaping(tsk->pid); 573 return false; 574 } 575 576 /* 577 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't 578 * work on the mm anymore. The check for MMF_OOM_SKIP must run 579 * under mmap_lock for reading because it serializes against the 580 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap(). 581 */ 582 if (test_bit(MMF_OOM_SKIP, &mm->flags)) { 583 trace_skip_task_reaping(tsk->pid); 584 goto out_unlock; 585 } 586 587 trace_start_task_reaping(tsk->pid); 588 589 /* failed to reap part of the address space. Try again later */ 590 ret = __oom_reap_task_mm(mm); 591 if (!ret) 592 goto out_finish; 593 594 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", 595 task_pid_nr(tsk), tsk->comm, 596 K(get_mm_counter(mm, MM_ANONPAGES)), 597 K(get_mm_counter(mm, MM_FILEPAGES)), 598 K(get_mm_counter(mm, MM_SHMEMPAGES))); 599 out_finish: 600 trace_finish_task_reaping(tsk->pid); 601 out_unlock: 602 mmap_read_unlock(mm); 603 604 return ret; 605 } 606 607 #define MAX_OOM_REAP_RETRIES 10 608 static void oom_reap_task(struct task_struct *tsk) 609 { 610 int attempts = 0; 611 struct mm_struct *mm = tsk->signal->oom_mm; 612 613 /* Retry the mmap_read_trylock(mm) a few times */ 614 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm)) 615 schedule_timeout_idle(HZ/10); 616 617 if (attempts <= MAX_OOM_REAP_RETRIES || 618 test_bit(MMF_OOM_SKIP, &mm->flags)) 619 goto done; 620 621 pr_info("oom_reaper: unable to reap pid:%d (%s)\n", 622 task_pid_nr(tsk), tsk->comm); 623 sched_show_task(tsk); 624 debug_show_all_locks(); 625 626 done: 627 tsk->oom_reaper_list = NULL; 628 629 /* 630 * Hide this mm from OOM killer because it has been either reaped or 631 * somebody can't call mmap_write_unlock(mm). 632 */ 633 set_bit(MMF_OOM_SKIP, &mm->flags); 634 635 /* Drop a reference taken by queue_oom_reaper */ 636 put_task_struct(tsk); 637 } 638 639 static int oom_reaper(void *unused) 640 { 641 set_freezable(); 642 643 while (true) { 644 struct task_struct *tsk = NULL; 645 646 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL); 647 spin_lock_irq(&oom_reaper_lock); 648 if (oom_reaper_list != NULL) { 649 tsk = oom_reaper_list; 650 oom_reaper_list = tsk->oom_reaper_list; 651 } 652 spin_unlock_irq(&oom_reaper_lock); 653 654 if (tsk) 655 oom_reap_task(tsk); 656 } 657 658 return 0; 659 } 660 661 static void wake_oom_reaper(struct timer_list *timer) 662 { 663 struct task_struct *tsk = container_of(timer, struct task_struct, 664 oom_reaper_timer); 665 struct mm_struct *mm = tsk->signal->oom_mm; 666 unsigned long flags; 667 668 /* The victim managed to terminate on its own - see exit_mmap */ 669 if (test_bit(MMF_OOM_SKIP, &mm->flags)) { 670 put_task_struct(tsk); 671 return; 672 } 673 674 spin_lock_irqsave(&oom_reaper_lock, flags); 675 tsk->oom_reaper_list = oom_reaper_list; 676 oom_reaper_list = tsk; 677 spin_unlock_irqrestore(&oom_reaper_lock, flags); 678 trace_wake_reaper(tsk->pid); 679 wake_up(&oom_reaper_wait); 680 } 681 682 /* 683 * Give the OOM victim time to exit naturally before invoking the oom_reaping. 684 * The timers timeout is arbitrary... the longer it is, the longer the worst 685 * case scenario for the OOM can take. If it is too small, the oom_reaper can 686 * get in the way and release resources needed by the process exit path. 687 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped 688 * before the exit path is able to wake the futex waiters. 689 */ 690 #define OOM_REAPER_DELAY (2*HZ) 691 static void queue_oom_reaper(struct task_struct *tsk) 692 { 693 /* mm is already queued? */ 694 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags)) 695 return; 696 697 get_task_struct(tsk); 698 timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0); 699 tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY; 700 add_timer(&tsk->oom_reaper_timer); 701 } 702 703 #ifdef CONFIG_SYSCTL 704 static struct ctl_table vm_oom_kill_table[] = { 705 { 706 .procname = "panic_on_oom", 707 .data = &sysctl_panic_on_oom, 708 .maxlen = sizeof(sysctl_panic_on_oom), 709 .mode = 0644, 710 .proc_handler = proc_dointvec_minmax, 711 .extra1 = SYSCTL_ZERO, 712 .extra2 = SYSCTL_TWO, 713 }, 714 { 715 .procname = "oom_kill_allocating_task", 716 .data = &sysctl_oom_kill_allocating_task, 717 .maxlen = sizeof(sysctl_oom_kill_allocating_task), 718 .mode = 0644, 719 .proc_handler = proc_dointvec, 720 }, 721 { 722 .procname = "oom_dump_tasks", 723 .data = &sysctl_oom_dump_tasks, 724 .maxlen = sizeof(sysctl_oom_dump_tasks), 725 .mode = 0644, 726 .proc_handler = proc_dointvec, 727 }, 728 {} 729 }; 730 #endif 731 732 static int __init oom_init(void) 733 { 734 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper"); 735 #ifdef CONFIG_SYSCTL 736 register_sysctl_init("vm", vm_oom_kill_table); 737 #endif 738 return 0; 739 } 740 subsys_initcall(oom_init) 741 #else 742 static inline void queue_oom_reaper(struct task_struct *tsk) 743 { 744 } 745 #endif /* CONFIG_MMU */ 746 747 /** 748 * mark_oom_victim - mark the given task as OOM victim 749 * @tsk: task to mark 750 * 751 * Has to be called with oom_lock held and never after 752 * oom has been disabled already. 753 * 754 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either 755 * under task_lock or operate on the current). 756 */ 757 static void mark_oom_victim(struct task_struct *tsk) 758 { 759 struct mm_struct *mm = tsk->mm; 760 761 WARN_ON(oom_killer_disabled); 762 /* OOM killer might race with memcg OOM */ 763 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) 764 return; 765 766 /* oom_mm is bound to the signal struct life time. */ 767 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) { 768 mmgrab(tsk->signal->oom_mm); 769 set_bit(MMF_OOM_VICTIM, &mm->flags); 770 } 771 772 /* 773 * Make sure that the task is woken up from uninterruptible sleep 774 * if it is frozen because OOM killer wouldn't be able to free 775 * any memory and livelock. freezing_slow_path will tell the freezer 776 * that TIF_MEMDIE tasks should be ignored. 777 */ 778 __thaw_task(tsk); 779 atomic_inc(&oom_victims); 780 trace_mark_victim(tsk->pid); 781 } 782 783 /** 784 * exit_oom_victim - note the exit of an OOM victim 785 */ 786 void exit_oom_victim(void) 787 { 788 clear_thread_flag(TIF_MEMDIE); 789 790 if (!atomic_dec_return(&oom_victims)) 791 wake_up_all(&oom_victims_wait); 792 } 793 794 /** 795 * oom_killer_enable - enable OOM killer 796 */ 797 void oom_killer_enable(void) 798 { 799 oom_killer_disabled = false; 800 pr_info("OOM killer enabled.\n"); 801 } 802 803 /** 804 * oom_killer_disable - disable OOM killer 805 * @timeout: maximum timeout to wait for oom victims in jiffies 806 * 807 * Forces all page allocations to fail rather than trigger OOM killer. 808 * Will block and wait until all OOM victims are killed or the given 809 * timeout expires. 810 * 811 * The function cannot be called when there are runnable user tasks because 812 * the userspace would see unexpected allocation failures as a result. Any 813 * new usage of this function should be consulted with MM people. 814 * 815 * Returns true if successful and false if the OOM killer cannot be 816 * disabled. 817 */ 818 bool oom_killer_disable(signed long timeout) 819 { 820 signed long ret; 821 822 /* 823 * Make sure to not race with an ongoing OOM killer. Check that the 824 * current is not killed (possibly due to sharing the victim's memory). 825 */ 826 if (mutex_lock_killable(&oom_lock)) 827 return false; 828 oom_killer_disabled = true; 829 mutex_unlock(&oom_lock); 830 831 ret = wait_event_interruptible_timeout(oom_victims_wait, 832 !atomic_read(&oom_victims), timeout); 833 if (ret <= 0) { 834 oom_killer_enable(); 835 return false; 836 } 837 pr_info("OOM killer disabled.\n"); 838 839 return true; 840 } 841 842 static inline bool __task_will_free_mem(struct task_struct *task) 843 { 844 struct signal_struct *sig = task->signal; 845 846 /* 847 * A coredumping process may sleep for an extended period in 848 * coredump_task_exit(), so the oom killer cannot assume that 849 * the process will promptly exit and release memory. 850 */ 851 if (sig->core_state) 852 return false; 853 854 if (sig->flags & SIGNAL_GROUP_EXIT) 855 return true; 856 857 if (thread_group_empty(task) && (task->flags & PF_EXITING)) 858 return true; 859 860 return false; 861 } 862 863 /* 864 * Checks whether the given task is dying or exiting and likely to 865 * release its address space. This means that all threads and processes 866 * sharing the same mm have to be killed or exiting. 867 * Caller has to make sure that task->mm is stable (hold task_lock or 868 * it operates on the current). 869 */ 870 static bool task_will_free_mem(struct task_struct *task) 871 { 872 struct mm_struct *mm = task->mm; 873 struct task_struct *p; 874 bool ret = true; 875 876 /* 877 * Skip tasks without mm because it might have passed its exit_mm and 878 * exit_oom_victim. oom_reaper could have rescued that but do not rely 879 * on that for now. We can consider find_lock_task_mm in future. 880 */ 881 if (!mm) 882 return false; 883 884 if (!__task_will_free_mem(task)) 885 return false; 886 887 /* 888 * This task has already been drained by the oom reaper so there are 889 * only small chances it will free some more 890 */ 891 if (test_bit(MMF_OOM_SKIP, &mm->flags)) 892 return false; 893 894 if (atomic_read(&mm->mm_users) <= 1) 895 return true; 896 897 /* 898 * Make sure that all tasks which share the mm with the given tasks 899 * are dying as well to make sure that a) nobody pins its mm and 900 * b) the task is also reapable by the oom reaper. 901 */ 902 rcu_read_lock(); 903 for_each_process(p) { 904 if (!process_shares_mm(p, mm)) 905 continue; 906 if (same_thread_group(task, p)) 907 continue; 908 ret = __task_will_free_mem(p); 909 if (!ret) 910 break; 911 } 912 rcu_read_unlock(); 913 914 return ret; 915 } 916 917 static void __oom_kill_process(struct task_struct *victim, const char *message) 918 { 919 struct task_struct *p; 920 struct mm_struct *mm; 921 bool can_oom_reap = true; 922 923 p = find_lock_task_mm(victim); 924 if (!p) { 925 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n", 926 message, task_pid_nr(victim), victim->comm); 927 put_task_struct(victim); 928 return; 929 } else if (victim != p) { 930 get_task_struct(p); 931 put_task_struct(victim); 932 victim = p; 933 } 934 935 /* Get a reference to safely compare mm after task_unlock(victim) */ 936 mm = victim->mm; 937 mmgrab(mm); 938 939 /* Raise event before sending signal: task reaper must see this */ 940 count_vm_event(OOM_KILL); 941 memcg_memory_event_mm(mm, MEMCG_OOM_KILL); 942 943 /* 944 * We should send SIGKILL before granting access to memory reserves 945 * in order to prevent the OOM victim from depleting the memory 946 * reserves from the user space under its control. 947 */ 948 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID); 949 mark_oom_victim(victim); 950 pr_err("%s: Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB, UID:%u pgtables:%lukB oom_score_adj:%hd\n", 951 message, task_pid_nr(victim), victim->comm, K(mm->total_vm), 952 K(get_mm_counter(mm, MM_ANONPAGES)), 953 K(get_mm_counter(mm, MM_FILEPAGES)), 954 K(get_mm_counter(mm, MM_SHMEMPAGES)), 955 from_kuid(&init_user_ns, task_uid(victim)), 956 mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj); 957 task_unlock(victim); 958 959 /* 960 * Kill all user processes sharing victim->mm in other thread groups, if 961 * any. They don't get access to memory reserves, though, to avoid 962 * depletion of all memory. This prevents mm->mmap_lock livelock when an 963 * oom killed thread cannot exit because it requires the semaphore and 964 * its contended by another thread trying to allocate memory itself. 965 * That thread will now get access to memory reserves since it has a 966 * pending fatal signal. 967 */ 968 rcu_read_lock(); 969 for_each_process(p) { 970 if (!process_shares_mm(p, mm)) 971 continue; 972 if (same_thread_group(p, victim)) 973 continue; 974 if (is_global_init(p)) { 975 can_oom_reap = false; 976 set_bit(MMF_OOM_SKIP, &mm->flags); 977 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n", 978 task_pid_nr(victim), victim->comm, 979 task_pid_nr(p), p->comm); 980 continue; 981 } 982 /* 983 * No kthread_use_mm() user needs to read from the userspace so 984 * we are ok to reap it. 985 */ 986 if (unlikely(p->flags & PF_KTHREAD)) 987 continue; 988 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID); 989 } 990 rcu_read_unlock(); 991 992 if (can_oom_reap) 993 queue_oom_reaper(victim); 994 995 mmdrop(mm); 996 put_task_struct(victim); 997 } 998 #undef K 999 1000 /* 1001 * Kill provided task unless it's secured by setting 1002 * oom_score_adj to OOM_SCORE_ADJ_MIN. 1003 */ 1004 static int oom_kill_memcg_member(struct task_struct *task, void *message) 1005 { 1006 if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN && 1007 !is_global_init(task)) { 1008 get_task_struct(task); 1009 __oom_kill_process(task, message); 1010 } 1011 return 0; 1012 } 1013 1014 static void oom_kill_process(struct oom_control *oc, const char *message) 1015 { 1016 struct task_struct *victim = oc->chosen; 1017 struct mem_cgroup *oom_group; 1018 static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL, 1019 DEFAULT_RATELIMIT_BURST); 1020 1021 /* 1022 * If the task is already exiting, don't alarm the sysadmin or kill 1023 * its children or threads, just give it access to memory reserves 1024 * so it can die quickly 1025 */ 1026 task_lock(victim); 1027 if (task_will_free_mem(victim)) { 1028 mark_oom_victim(victim); 1029 queue_oom_reaper(victim); 1030 task_unlock(victim); 1031 put_task_struct(victim); 1032 return; 1033 } 1034 task_unlock(victim); 1035 1036 if (__ratelimit(&oom_rs)) 1037 dump_header(oc, victim); 1038 1039 /* 1040 * Do we need to kill the entire memory cgroup? 1041 * Or even one of the ancestor memory cgroups? 1042 * Check this out before killing the victim task. 1043 */ 1044 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg); 1045 1046 __oom_kill_process(victim, message); 1047 1048 /* 1049 * If necessary, kill all tasks in the selected memory cgroup. 1050 */ 1051 if (oom_group) { 1052 memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL); 1053 mem_cgroup_print_oom_group(oom_group); 1054 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member, 1055 (void *)message); 1056 mem_cgroup_put(oom_group); 1057 } 1058 } 1059 1060 /* 1061 * Determines whether the kernel must panic because of the panic_on_oom sysctl. 1062 */ 1063 static void check_panic_on_oom(struct oom_control *oc) 1064 { 1065 if (likely(!sysctl_panic_on_oom)) 1066 return; 1067 if (sysctl_panic_on_oom != 2) { 1068 /* 1069 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel 1070 * does not panic for cpuset, mempolicy, or memcg allocation 1071 * failures. 1072 */ 1073 if (oc->constraint != CONSTRAINT_NONE) 1074 return; 1075 } 1076 /* Do not panic for oom kills triggered by sysrq */ 1077 if (is_sysrq_oom(oc)) 1078 return; 1079 dump_header(oc, NULL); 1080 panic("Out of memory: %s panic_on_oom is enabled\n", 1081 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); 1082 } 1083 1084 static BLOCKING_NOTIFIER_HEAD(oom_notify_list); 1085 1086 int register_oom_notifier(struct notifier_block *nb) 1087 { 1088 return blocking_notifier_chain_register(&oom_notify_list, nb); 1089 } 1090 EXPORT_SYMBOL_GPL(register_oom_notifier); 1091 1092 int unregister_oom_notifier(struct notifier_block *nb) 1093 { 1094 return blocking_notifier_chain_unregister(&oom_notify_list, nb); 1095 } 1096 EXPORT_SYMBOL_GPL(unregister_oom_notifier); 1097 1098 /** 1099 * out_of_memory - kill the "best" process when we run out of memory 1100 * @oc: pointer to struct oom_control 1101 * 1102 * If we run out of memory, we have the choice between either 1103 * killing a random task (bad), letting the system crash (worse) 1104 * OR try to be smart about which process to kill. Note that we 1105 * don't have to be perfect here, we just have to be good. 1106 */ 1107 bool out_of_memory(struct oom_control *oc) 1108 { 1109 unsigned long freed = 0; 1110 1111 if (oom_killer_disabled) 1112 return false; 1113 1114 if (!is_memcg_oom(oc)) { 1115 blocking_notifier_call_chain(&oom_notify_list, 0, &freed); 1116 if (freed > 0 && !is_sysrq_oom(oc)) 1117 /* Got some memory back in the last second. */ 1118 return true; 1119 } 1120 1121 /* 1122 * If current has a pending SIGKILL or is exiting, then automatically 1123 * select it. The goal is to allow it to allocate so that it may 1124 * quickly exit and free its memory. 1125 */ 1126 if (task_will_free_mem(current)) { 1127 mark_oom_victim(current); 1128 queue_oom_reaper(current); 1129 return true; 1130 } 1131 1132 /* 1133 * The OOM killer does not compensate for IO-less reclaim. 1134 * pagefault_out_of_memory lost its gfp context so we have to 1135 * make sure exclude 0 mask - all other users should have at least 1136 * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to 1137 * invoke the OOM killer even if it is a GFP_NOFS allocation. 1138 */ 1139 if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc)) 1140 return true; 1141 1142 /* 1143 * Check if there were limitations on the allocation (only relevant for 1144 * NUMA and memcg) that may require different handling. 1145 */ 1146 oc->constraint = constrained_alloc(oc); 1147 if (oc->constraint != CONSTRAINT_MEMORY_POLICY) 1148 oc->nodemask = NULL; 1149 check_panic_on_oom(oc); 1150 1151 if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task && 1152 current->mm && !oom_unkillable_task(current) && 1153 oom_cpuset_eligible(current, oc) && 1154 current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) { 1155 get_task_struct(current); 1156 oc->chosen = current; 1157 oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)"); 1158 return true; 1159 } 1160 1161 select_bad_process(oc); 1162 /* Found nothing?!?! */ 1163 if (!oc->chosen) { 1164 dump_header(oc, NULL); 1165 pr_warn("Out of memory and no killable processes...\n"); 1166 /* 1167 * If we got here due to an actual allocation at the 1168 * system level, we cannot survive this and will enter 1169 * an endless loop in the allocator. Bail out now. 1170 */ 1171 if (!is_sysrq_oom(oc) && !is_memcg_oom(oc)) 1172 panic("System is deadlocked on memory\n"); 1173 } 1174 if (oc->chosen && oc->chosen != (void *)-1UL) 1175 oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" : 1176 "Memory cgroup out of memory"); 1177 return !!oc->chosen; 1178 } 1179 1180 /* 1181 * The pagefault handler calls here because some allocation has failed. We have 1182 * to take care of the memcg OOM here because this is the only safe context without 1183 * any locks held but let the oom killer triggered from the allocation context care 1184 * about the global OOM. 1185 */ 1186 void pagefault_out_of_memory(void) 1187 { 1188 static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL, 1189 DEFAULT_RATELIMIT_BURST); 1190 1191 if (mem_cgroup_oom_synchronize(true)) 1192 return; 1193 1194 if (fatal_signal_pending(current)) 1195 return; 1196 1197 if (__ratelimit(&pfoom_rs)) 1198 pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n"); 1199 } 1200 1201 SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags) 1202 { 1203 #ifdef CONFIG_MMU 1204 struct mm_struct *mm = NULL; 1205 struct task_struct *task; 1206 struct task_struct *p; 1207 unsigned int f_flags; 1208 bool reap = false; 1209 long ret = 0; 1210 1211 if (flags) 1212 return -EINVAL; 1213 1214 task = pidfd_get_task(pidfd, &f_flags); 1215 if (IS_ERR(task)) 1216 return PTR_ERR(task); 1217 1218 /* 1219 * Make sure to choose a thread which still has a reference to mm 1220 * during the group exit 1221 */ 1222 p = find_lock_task_mm(task); 1223 if (!p) { 1224 ret = -ESRCH; 1225 goto put_task; 1226 } 1227 1228 mm = p->mm; 1229 mmgrab(mm); 1230 1231 if (task_will_free_mem(p)) 1232 reap = true; 1233 else { 1234 /* Error only if the work has not been done already */ 1235 if (!test_bit(MMF_OOM_SKIP, &mm->flags)) 1236 ret = -EINVAL; 1237 } 1238 task_unlock(p); 1239 1240 if (!reap) 1241 goto drop_mm; 1242 1243 if (mmap_read_lock_killable(mm)) { 1244 ret = -EINTR; 1245 goto drop_mm; 1246 } 1247 /* 1248 * Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure 1249 * possible change in exit_mmap is seen 1250 */ 1251 if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm)) 1252 ret = -EAGAIN; 1253 mmap_read_unlock(mm); 1254 1255 drop_mm: 1256 mmdrop(mm); 1257 put_task: 1258 put_task_struct(task); 1259 return ret; 1260 #else 1261 return -ENOSYS; 1262 #endif /* CONFIG_MMU */ 1263 } 1264