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
  55static int sysctl_panic_on_oom;
  56static int sysctl_oom_kill_allocating_task;
  57static 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 */
  67DEFINE_MUTEX(oom_lock);
  68/* Serializes oom_score_adj and oom_score_adj_min updates */
  69DEFINE_MUTEX(oom_adj_mutex);
  70
  71static 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 */
  89static 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
 121static 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 */
 133struct 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;
 146found:
 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 */
 156static 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. */
 162static 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*/
 177static 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 */
 201long 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
 241static 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 */
 251static 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
 308static 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
 345select:
 346	if (oc->chosen)
 347		put_task_struct(oc->chosen);
 348	get_task_struct(task);
 349	oc->chosen = task;
 350	oc->chosen_points = points;
 351next:
 352	return 0;
 353abort:
 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 */
 364static 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
 381static 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 */
 423static 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
 440static 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
 452static 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 */
 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#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 */
 490bool 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 */
 507static struct task_struct *oom_reaper_th;
 508static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
 509static struct task_struct *oom_reaper_list;
 510static DEFINE_SPINLOCK(oom_reaper_lock);
 511
 512static 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						vma, 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 */
 568static 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)));
 600out_finish:
 601	trace_finish_task_reaping(tsk->pid);
 602out_unlock:
 603	mmap_read_unlock(mm);
 604
 605	return ret;
 606}
 607
 608#define MAX_OOM_REAP_RETRIES 10
 609static 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
 627done:
 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
 640static 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
 662static 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)
 692static 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
 705static 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
 733static 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}
 741subsys_initcall(oom_init)
 742#else
 743static 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 */
 758static 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 */
 785void 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 */
 796void 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 */
 817bool 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
 841static 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 */
 869static 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
 916static 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 */
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, 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 */
1062static 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
1083static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
1084
1085int register_oom_notifier(struct notifier_block *nb)
1086{
1087	return blocking_notifier_chain_register(&oom_notify_list, nb);
1088}
1089EXPORT_SYMBOL_GPL(register_oom_notifier);
1090
1091int unregister_oom_notifier(struct notifier_block *nb)
1092{
1093	return blocking_notifier_chain_unregister(&oom_notify_list, nb);
1094}
1095EXPORT_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 */
1106bool 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 */
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}