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