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, gfp_zone(oc->gfp_mask)); 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 static bool __oom_reap_task_mm(struct mm_struct *mm) 513 { 514 struct vm_area_struct *vma; 515 bool ret = true; 516 VMA_ITERATOR(vmi, mm, 0); 517 518 /* 519 * Tell all users of get_user/copy_from_user etc... that the content 520 * is no longer stable. No barriers really needed because unmapping 521 * should imply barriers already and the reader would hit a page fault 522 * if it stumbled over a reaped memory. 523 */ 524 set_bit(MMF_UNSTABLE, &mm->flags); 525 526 for_each_vma(vmi, vma) { 527 if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP)) 528 continue; 529 530 /* 531 * Only anonymous pages have a good chance to be dropped 532 * without additional steps which we cannot afford as we 533 * are OOM already. 534 * 535 * We do not even care about fs backed pages because all 536 * which are reclaimable have already been reclaimed and 537 * we do not want to block exit_mmap by keeping mm ref 538 * count elevated without a good reason. 539 */ 540 if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) { 541 struct mmu_notifier_range range; 542 struct mmu_gather tlb; 543 544 mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0, 545 mm, vma->vm_start, 546 vma->vm_end); 547 tlb_gather_mmu(&tlb, mm); 548 if (mmu_notifier_invalidate_range_start_nonblock(&range)) { 549 tlb_finish_mmu(&tlb); 550 ret = false; 551 continue; 552 } 553 unmap_page_range(&tlb, vma, range.start, range.end, NULL); 554 mmu_notifier_invalidate_range_end(&range); 555 tlb_finish_mmu(&tlb); 556 } 557 } 558 559 return ret; 560 } 561 562 /* 563 * Reaps the address space of the give task. 564 * 565 * Returns true on success and false if none or part of the address space 566 * has been reclaimed and the caller should retry later. 567 */ 568 static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm) 569 { 570 bool ret = true; 571 572 if (!mmap_read_trylock(mm)) { 573 trace_skip_task_reaping(tsk->pid); 574 return false; 575 } 576 577 /* 578 * MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't 579 * work on the mm anymore. The check for MMF_OOM_SKIP must run 580 * under mmap_lock for reading because it serializes against the 581 * mmap_write_lock();mmap_write_unlock() cycle in exit_mmap(). 582 */ 583 if (test_bit(MMF_OOM_SKIP, &mm->flags)) { 584 trace_skip_task_reaping(tsk->pid); 585 goto out_unlock; 586 } 587 588 trace_start_task_reaping(tsk->pid); 589 590 /* failed to reap part of the address space. Try again later */ 591 ret = __oom_reap_task_mm(mm); 592 if (!ret) 593 goto out_finish; 594 595 pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n", 596 task_pid_nr(tsk), tsk->comm, 597 K(get_mm_counter(mm, MM_ANONPAGES)), 598 K(get_mm_counter(mm, MM_FILEPAGES)), 599 K(get_mm_counter(mm, MM_SHMEMPAGES))); 600 out_finish: 601 trace_finish_task_reaping(tsk->pid); 602 out_unlock: 603 mmap_read_unlock(mm); 604 605 return ret; 606 } 607 608 #define MAX_OOM_REAP_RETRIES 10 609 static void oom_reap_task(struct task_struct *tsk) 610 { 611 int attempts = 0; 612 struct mm_struct *mm = tsk->signal->oom_mm; 613 614 /* Retry the mmap_read_trylock(mm) a few times */ 615 while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm)) 616 schedule_timeout_idle(HZ/10); 617 618 if (attempts <= MAX_OOM_REAP_RETRIES || 619 test_bit(MMF_OOM_SKIP, &mm->flags)) 620 goto done; 621 622 pr_info("oom_reaper: unable to reap pid:%d (%s)\n", 623 task_pid_nr(tsk), tsk->comm); 624 sched_show_task(tsk); 625 debug_show_all_locks(); 626 627 done: 628 tsk->oom_reaper_list = NULL; 629 630 /* 631 * Hide this mm from OOM killer because it has been either reaped or 632 * somebody can't call mmap_write_unlock(mm). 633 */ 634 set_bit(MMF_OOM_SKIP, &mm->flags); 635 636 /* Drop a reference taken by queue_oom_reaper */ 637 put_task_struct(tsk); 638 } 639 640 static int oom_reaper(void *unused) 641 { 642 set_freezable(); 643 644 while (true) { 645 struct task_struct *tsk = NULL; 646 647 wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL); 648 spin_lock_irq(&oom_reaper_lock); 649 if (oom_reaper_list != NULL) { 650 tsk = oom_reaper_list; 651 oom_reaper_list = tsk->oom_reaper_list; 652 } 653 spin_unlock_irq(&oom_reaper_lock); 654 655 if (tsk) 656 oom_reap_task(tsk); 657 } 658 659 return 0; 660 } 661 662 static void wake_oom_reaper(struct timer_list *timer) 663 { 664 struct task_struct *tsk = container_of(timer, struct task_struct, 665 oom_reaper_timer); 666 struct mm_struct *mm = tsk->signal->oom_mm; 667 unsigned long flags; 668 669 /* The victim managed to terminate on its own - see exit_mmap */ 670 if (test_bit(MMF_OOM_SKIP, &mm->flags)) { 671 put_task_struct(tsk); 672 return; 673 } 674 675 spin_lock_irqsave(&oom_reaper_lock, flags); 676 tsk->oom_reaper_list = oom_reaper_list; 677 oom_reaper_list = tsk; 678 spin_unlock_irqrestore(&oom_reaper_lock, flags); 679 trace_wake_reaper(tsk->pid); 680 wake_up(&oom_reaper_wait); 681 } 682 683 /* 684 * Give the OOM victim time to exit naturally before invoking the oom_reaping. 685 * The timers timeout is arbitrary... the longer it is, the longer the worst 686 * case scenario for the OOM can take. If it is too small, the oom_reaper can 687 * get in the way and release resources needed by the process exit path. 688 * e.g. The futex robust list can sit in Anon|Private memory that gets reaped 689 * before the exit path is able to wake the futex waiters. 690 */ 691 #define OOM_REAPER_DELAY (2*HZ) 692 static void queue_oom_reaper(struct task_struct *tsk) 693 { 694 /* mm is already queued? */ 695 if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags)) 696 return; 697 698 get_task_struct(tsk); 699 timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0); 700 tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY; 701 add_timer(&tsk->oom_reaper_timer); 702 } 703 704 #ifdef CONFIG_SYSCTL 705 static struct ctl_table vm_oom_kill_table[] = { 706 { 707 .procname = "panic_on_oom", 708 .data = &sysctl_panic_on_oom, 709 .maxlen = sizeof(sysctl_panic_on_oom), 710 .mode = 0644, 711 .proc_handler = proc_dointvec_minmax, 712 .extra1 = SYSCTL_ZERO, 713 .extra2 = SYSCTL_TWO, 714 }, 715 { 716 .procname = "oom_kill_allocating_task", 717 .data = &sysctl_oom_kill_allocating_task, 718 .maxlen = sizeof(sysctl_oom_kill_allocating_task), 719 .mode = 0644, 720 .proc_handler = proc_dointvec, 721 }, 722 { 723 .procname = "oom_dump_tasks", 724 .data = &sysctl_oom_dump_tasks, 725 .maxlen = sizeof(sysctl_oom_dump_tasks), 726 .mode = 0644, 727 .proc_handler = proc_dointvec, 728 }, 729 {} 730 }; 731 #endif 732 733 static int __init oom_init(void) 734 { 735 oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper"); 736 #ifdef CONFIG_SYSCTL 737 register_sysctl_init("vm", vm_oom_kill_table); 738 #endif 739 return 0; 740 } 741 subsys_initcall(oom_init) 742 #else 743 static inline void queue_oom_reaper(struct task_struct *tsk) 744 { 745 } 746 #endif /* CONFIG_MMU */ 747 748 /** 749 * mark_oom_victim - mark the given task as OOM victim 750 * @tsk: task to mark 751 * 752 * Has to be called with oom_lock held and never after 753 * oom has been disabled already. 754 * 755 * tsk->mm has to be non NULL and caller has to guarantee it is stable (either 756 * under task_lock or operate on the current). 757 */ 758 static void mark_oom_victim(struct task_struct *tsk) 759 { 760 struct mm_struct *mm = tsk->mm; 761 762 WARN_ON(oom_killer_disabled); 763 /* OOM killer might race with memcg OOM */ 764 if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE)) 765 return; 766 767 /* oom_mm is bound to the signal struct life time. */ 768 if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm)) 769 mmgrab(tsk->signal->oom_mm); 770 771 /* 772 * Make sure that the task is woken up from uninterruptible sleep 773 * if it is frozen because OOM killer wouldn't be able to free 774 * any memory and livelock. freezing_slow_path will tell the freezer 775 * that TIF_MEMDIE tasks should be ignored. 776 */ 777 __thaw_task(tsk); 778 atomic_inc(&oom_victims); 779 trace_mark_victim(tsk->pid); 780 } 781 782 /** 783 * exit_oom_victim - note the exit of an OOM victim 784 */ 785 void exit_oom_victim(void) 786 { 787 clear_thread_flag(TIF_MEMDIE); 788 789 if (!atomic_dec_return(&oom_victims)) 790 wake_up_all(&oom_victims_wait); 791 } 792 793 /** 794 * oom_killer_enable - enable OOM killer 795 */ 796 void oom_killer_enable(void) 797 { 798 oom_killer_disabled = false; 799 pr_info("OOM killer enabled.\n"); 800 } 801 802 /** 803 * oom_killer_disable - disable OOM killer 804 * @timeout: maximum timeout to wait for oom victims in jiffies 805 * 806 * Forces all page allocations to fail rather than trigger OOM killer. 807 * Will block and wait until all OOM victims are killed or the given 808 * timeout expires. 809 * 810 * The function cannot be called when there are runnable user tasks because 811 * the userspace would see unexpected allocation failures as a result. Any 812 * new usage of this function should be consulted with MM people. 813 * 814 * Returns true if successful and false if the OOM killer cannot be 815 * disabled. 816 */ 817 bool oom_killer_disable(signed long timeout) 818 { 819 signed long ret; 820 821 /* 822 * Make sure to not race with an ongoing OOM killer. Check that the 823 * current is not killed (possibly due to sharing the victim's memory). 824 */ 825 if (mutex_lock_killable(&oom_lock)) 826 return false; 827 oom_killer_disabled = true; 828 mutex_unlock(&oom_lock); 829 830 ret = wait_event_interruptible_timeout(oom_victims_wait, 831 !atomic_read(&oom_victims), timeout); 832 if (ret <= 0) { 833 oom_killer_enable(); 834 return false; 835 } 836 pr_info("OOM killer disabled.\n"); 837 838 return true; 839 } 840 841 static inline bool __task_will_free_mem(struct task_struct *task) 842 { 843 struct signal_struct *sig = task->signal; 844 845 /* 846 * A coredumping process may sleep for an extended period in 847 * coredump_task_exit(), so the oom killer cannot assume that 848 * the process will promptly exit and release memory. 849 */ 850 if (sig->core_state) 851 return false; 852 853 if (sig->flags & SIGNAL_GROUP_EXIT) 854 return true; 855 856 if (thread_group_empty(task) && (task->flags & PF_EXITING)) 857 return true; 858 859 return false; 860 } 861 862 /* 863 * Checks whether the given task is dying or exiting and likely to 864 * release its address space. This means that all threads and processes 865 * sharing the same mm have to be killed or exiting. 866 * Caller has to make sure that task->mm is stable (hold task_lock or 867 * it operates on the current). 868 */ 869 static bool task_will_free_mem(struct task_struct *task) 870 { 871 struct mm_struct *mm = task->mm; 872 struct task_struct *p; 873 bool ret = true; 874 875 /* 876 * Skip tasks without mm because it might have passed its exit_mm and 877 * exit_oom_victim. oom_reaper could have rescued that but do not rely 878 * on that for now. We can consider find_lock_task_mm in future. 879 */ 880 if (!mm) 881 return false; 882 883 if (!__task_will_free_mem(task)) 884 return false; 885 886 /* 887 * This task has already been drained by the oom reaper so there are 888 * only small chances it will free some more 889 */ 890 if (test_bit(MMF_OOM_SKIP, &mm->flags)) 891 return false; 892 893 if (atomic_read(&mm->mm_users) <= 1) 894 return true; 895 896 /* 897 * Make sure that all tasks which share the mm with the given tasks 898 * are dying as well to make sure that a) nobody pins its mm and 899 * b) the task is also reapable by the oom reaper. 900 */ 901 rcu_read_lock(); 902 for_each_process(p) { 903 if (!process_shares_mm(p, mm)) 904 continue; 905 if (same_thread_group(task, p)) 906 continue; 907 ret = __task_will_free_mem(p); 908 if (!ret) 909 break; 910 } 911 rcu_read_unlock(); 912 913 return ret; 914 } 915 916 static void __oom_kill_process(struct task_struct *victim, const char *message) 917 { 918 struct task_struct *p; 919 struct mm_struct *mm; 920 bool can_oom_reap = true; 921 922 p = find_lock_task_mm(victim); 923 if (!p) { 924 pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n", 925 message, task_pid_nr(victim), victim->comm); 926 put_task_struct(victim); 927 return; 928 } else if (victim != p) { 929 get_task_struct(p); 930 put_task_struct(victim); 931 victim = p; 932 } 933 934 /* Get a reference to safely compare mm after task_unlock(victim) */ 935 mm = victim->mm; 936 mmgrab(mm); 937 938 /* Raise event before sending signal: task reaper must see this */ 939 count_vm_event(OOM_KILL); 940 memcg_memory_event_mm(mm, MEMCG_OOM_KILL); 941 942 /* 943 * We should send SIGKILL before granting access to memory reserves 944 * in order to prevent the OOM victim from depleting the memory 945 * reserves from the user space under its control. 946 */ 947 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID); 948 mark_oom_victim(victim); 949 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", 950 message, task_pid_nr(victim), victim->comm, K(mm->total_vm), 951 K(get_mm_counter(mm, MM_ANONPAGES)), 952 K(get_mm_counter(mm, MM_FILEPAGES)), 953 K(get_mm_counter(mm, MM_SHMEMPAGES)), 954 from_kuid(&init_user_ns, task_uid(victim)), 955 mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj); 956 task_unlock(victim); 957 958 /* 959 * Kill all user processes sharing victim->mm in other thread groups, if 960 * any. They don't get access to memory reserves, though, to avoid 961 * depletion of all memory. This prevents mm->mmap_lock livelock when an 962 * oom killed thread cannot exit because it requires the semaphore and 963 * its contended by another thread trying to allocate memory itself. 964 * That thread will now get access to memory reserves since it has a 965 * pending fatal signal. 966 */ 967 rcu_read_lock(); 968 for_each_process(p) { 969 if (!process_shares_mm(p, mm)) 970 continue; 971 if (same_thread_group(p, victim)) 972 continue; 973 if (is_global_init(p)) { 974 can_oom_reap = false; 975 set_bit(MMF_OOM_SKIP, &mm->flags); 976 pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n", 977 task_pid_nr(victim), victim->comm, 978 task_pid_nr(p), p->comm); 979 continue; 980 } 981 /* 982 * No kthread_use_mm() user needs to read from the userspace so 983 * we are ok to reap it. 984 */ 985 if (unlikely(p->flags & PF_KTHREAD)) 986 continue; 987 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID); 988 } 989 rcu_read_unlock(); 990 991 if (can_oom_reap) 992 queue_oom_reaper(victim); 993 994 mmdrop(mm); 995 put_task_struct(victim); 996 } 997 #undef K 998 999 /* 1000 * Kill provided task unless it's secured by setting 1001 * oom_score_adj to OOM_SCORE_ADJ_MIN. 1002 */ 1003 static 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 1013 static 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, victim); 1037 1038 /* 1039 * Do we need to kill the entire memory cgroup? 1040 * Or even one of the ancestor memory cgroups? 1041 * Check this out before killing the victim task. 1042 */ 1043 oom_group = mem_cgroup_get_oom_group(victim, oc->memcg); 1044 1045 __oom_kill_process(victim, message); 1046 1047 /* 1048 * If necessary, kill all tasks in the selected memory cgroup. 1049 */ 1050 if (oom_group) { 1051 memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL); 1052 mem_cgroup_print_oom_group(oom_group); 1053 mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member, 1054 (void *)message); 1055 mem_cgroup_put(oom_group); 1056 } 1057 } 1058 1059 /* 1060 * Determines whether the kernel must panic because of the panic_on_oom sysctl. 1061 */ 1062 static void check_panic_on_oom(struct oom_control *oc) 1063 { 1064 if (likely(!sysctl_panic_on_oom)) 1065 return; 1066 if (sysctl_panic_on_oom != 2) { 1067 /* 1068 * panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel 1069 * does not panic for cpuset, mempolicy, or memcg allocation 1070 * failures. 1071 */ 1072 if (oc->constraint != CONSTRAINT_NONE) 1073 return; 1074 } 1075 /* Do not panic for oom kills triggered by sysrq */ 1076 if (is_sysrq_oom(oc)) 1077 return; 1078 dump_header(oc, NULL); 1079 panic("Out of memory: %s panic_on_oom is enabled\n", 1080 sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide"); 1081 } 1082 1083 static BLOCKING_NOTIFIER_HEAD(oom_notify_list); 1084 1085 int register_oom_notifier(struct notifier_block *nb) 1086 { 1087 return blocking_notifier_chain_register(&oom_notify_list, nb); 1088 } 1089 EXPORT_SYMBOL_GPL(register_oom_notifier); 1090 1091 int unregister_oom_notifier(struct notifier_block *nb) 1092 { 1093 return blocking_notifier_chain_unregister(&oom_notify_list, nb); 1094 } 1095 EXPORT_SYMBOL_GPL(unregister_oom_notifier); 1096 1097 /** 1098 * out_of_memory - kill the "best" process when we run out of memory 1099 * @oc: pointer to struct oom_control 1100 * 1101 * If we run out of memory, we have the choice between either 1102 * killing a random task (bad), letting the system crash (worse) 1103 * OR try to be smart about which process to kill. Note that we 1104 * don't have to be perfect here, we just have to be good. 1105 */ 1106 bool out_of_memory(struct oom_control *oc) 1107 { 1108 unsigned long freed = 0; 1109 1110 if (oom_killer_disabled) 1111 return false; 1112 1113 if (!is_memcg_oom(oc)) { 1114 blocking_notifier_call_chain(&oom_notify_list, 0, &freed); 1115 if (freed > 0 && !is_sysrq_oom(oc)) 1116 /* Got some memory back in the last second. */ 1117 return true; 1118 } 1119 1120 /* 1121 * If current has a pending SIGKILL or is exiting, then automatically 1122 * select it. The goal is to allow it to allocate so that it may 1123 * quickly exit and free its memory. 1124 */ 1125 if (task_will_free_mem(current)) { 1126 mark_oom_victim(current); 1127 queue_oom_reaper(current); 1128 return true; 1129 } 1130 1131 /* 1132 * The OOM killer does not compensate for IO-less reclaim. 1133 * pagefault_out_of_memory lost its gfp context so we have to 1134 * make sure exclude 0 mask - all other users should have at least 1135 * ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to 1136 * invoke the OOM killer even if it is a GFP_NOFS allocation. 1137 */ 1138 if (oc->gfp_mask && !(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, NULL); 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 */ 1185 void 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 1200 SYSCALL_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 1254 drop_mm: 1255 mmdrop(mm); 1256 put_task: 1257 put_task_struct(task); 1258 return ret; 1259 #else 1260 return -ENOSYS; 1261 #endif /* CONFIG_MMU */ 1262 } 1263