linux-stable/mm/oom_kill.c
Michal Hocko 974f4367dd mm: reduce noise in show_mem for lowmem allocations
While discussing early DMA pool pre-allocation failure with Christoph [1]
I have realized that the allocation failure warning is rather noisy for
constrained allocations like GFP_DMA{32}.  Those zones are usually not
populated on all nodes very often as their memory ranges are constrained.

This is an attempt to reduce the ballast that doesn't provide any relevant
information for those allocation failures investigation.  Please note that
I have only compile tested it (in my default config setup) and I am
throwing it mostly to see what people think about it.

[1] http://lkml.kernel.org/r/20220817060647.1032426-1-hch@lst.de

[mhocko@suse.com: update]
  Link: https://lkml.kernel.org/r/Yw29bmJTIkKogTiW@dhcp22.suse.cz
[mhocko@suse.com: fix build]
[akpm@linux-foundation.org: fix it for mapletree]
[akpm@linux-foundation.org: update it for Michal's update]
[mhocko@suse.com: fix arch/powerpc/xmon/xmon.c]
  Link: https://lkml.kernel.org/r/Ywh3C4dKB9B93jIy@dhcp22.suse.cz
[akpm@linux-foundation.org: fix arch/sparc/kernel/setup_32.c]
Link: https://lkml.kernel.org/r/YwScVmVofIZkopkF@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-09-26 19:46:29 -07:00

1262 lines
34 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* linux/mm/oom_kill.c
*
* Copyright (C) 1998,2000 Rik van Riel
* Thanks go out to Claus Fischer for some serious inspiration and
* for goading me into coding this file...
* Copyright (C) 2010 Google, Inc.
* Rewritten by David Rientjes
*
* The routines in this file are used to kill a process when
* we're seriously out of memory. This gets called from __alloc_pages()
* in mm/page_alloc.c when we really run out of memory.
*
* Since we won't call these routines often (on a well-configured
* machine) this file will double as a 'coding guide' and a signpost
* for newbie kernel hackers. It features several pointers to major
* kernel subsystems and hints as to where to find out what things do.
*/
#include <linux/oom.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/gfp.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/coredump.h>
#include <linux/sched/task.h>
#include <linux/sched/debug.h>
#include <linux/swap.h>
#include <linux/syscalls.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
#include <linux/cpuset.h>
#include <linux/export.h>
#include <linux/notifier.h>
#include <linux/memcontrol.h>
#include <linux/mempolicy.h>
#include <linux/security.h>
#include <linux/ptrace.h>
#include <linux/freezer.h>
#include <linux/ftrace.h>
#include <linux/ratelimit.h>
#include <linux/kthread.h>
#include <linux/init.h>
#include <linux/mmu_notifier.h>
#include <asm/tlb.h>
#include "internal.h"
#include "slab.h"
#define CREATE_TRACE_POINTS
#include <trace/events/oom.h>
static int sysctl_panic_on_oom;
static int sysctl_oom_kill_allocating_task;
static int sysctl_oom_dump_tasks = 1;
/*
* Serializes oom killer invocations (out_of_memory()) from all contexts to
* prevent from over eager oom killing (e.g. when the oom killer is invoked
* from different domains).
*
* oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
* and mark_oom_victim
*/
DEFINE_MUTEX(oom_lock);
/* Serializes oom_score_adj and oom_score_adj_min updates */
DEFINE_MUTEX(oom_adj_mutex);
static inline bool is_memcg_oom(struct oom_control *oc)
{
return oc->memcg != NULL;
}
#ifdef CONFIG_NUMA
/**
* oom_cpuset_eligible() - check task eligibility for kill
* @start: task struct of which task to consider
* @oc: pointer to struct oom_control
*
* Task eligibility is determined by whether or not a candidate task, @tsk,
* shares the same mempolicy nodes as current if it is bound by such a policy
* and whether or not it has the same set of allowed cpuset nodes.
*
* This function is assuming oom-killer context and 'current' has triggered
* the oom-killer.
*/
static bool oom_cpuset_eligible(struct task_struct *start,
struct oom_control *oc)
{
struct task_struct *tsk;
bool ret = false;
const nodemask_t *mask = oc->nodemask;
rcu_read_lock();
for_each_thread(start, tsk) {
if (mask) {
/*
* If this is a mempolicy constrained oom, tsk's
* cpuset is irrelevant. Only return true if its
* mempolicy intersects current, otherwise it may be
* needlessly killed.
*/
ret = mempolicy_in_oom_domain(tsk, mask);
} else {
/*
* This is not a mempolicy constrained oom, so only
* check the mems of tsk's cpuset.
*/
ret = cpuset_mems_allowed_intersects(current, tsk);
}
if (ret)
break;
}
rcu_read_unlock();
return ret;
}
#else
static bool oom_cpuset_eligible(struct task_struct *tsk, struct oom_control *oc)
{
return true;
}
#endif /* CONFIG_NUMA */
/*
* The process p may have detached its own ->mm while exiting or through
* kthread_use_mm(), but one or more of its subthreads may still have a valid
* pointer. Return p, or any of its subthreads with a valid ->mm, with
* task_lock() held.
*/
struct task_struct *find_lock_task_mm(struct task_struct *p)
{
struct task_struct *t;
rcu_read_lock();
for_each_thread(p, t) {
task_lock(t);
if (likely(t->mm))
goto found;
task_unlock(t);
}
t = NULL;
found:
rcu_read_unlock();
return t;
}
/*
* order == -1 means the oom kill is required by sysrq, otherwise only
* for display purposes.
*/
static inline bool is_sysrq_oom(struct oom_control *oc)
{
return oc->order == -1;
}
/* return true if the task is not adequate as candidate victim task. */
static bool oom_unkillable_task(struct task_struct *p)
{
if (is_global_init(p))
return true;
if (p->flags & PF_KTHREAD)
return true;
return false;
}
/*
* Check whether unreclaimable slab amount is greater than
* all user memory(LRU pages).
* dump_unreclaimable_slab() could help in the case that
* oom due to too much unreclaimable slab used by kernel.
*/
static bool should_dump_unreclaim_slab(void)
{
unsigned long nr_lru;
nr_lru = global_node_page_state(NR_ACTIVE_ANON) +
global_node_page_state(NR_INACTIVE_ANON) +
global_node_page_state(NR_ACTIVE_FILE) +
global_node_page_state(NR_INACTIVE_FILE) +
global_node_page_state(NR_ISOLATED_ANON) +
global_node_page_state(NR_ISOLATED_FILE) +
global_node_page_state(NR_UNEVICTABLE);
return (global_node_page_state_pages(NR_SLAB_UNRECLAIMABLE_B) > nr_lru);
}
/**
* oom_badness - heuristic function to determine which candidate task to kill
* @p: task struct of which task we should calculate
* @totalpages: total present RAM allowed for page allocation
*
* The heuristic for determining which task to kill is made to be as simple and
* predictable as possible. The goal is to return the highest value for the
* task consuming the most memory to avoid subsequent oom failures.
*/
long oom_badness(struct task_struct *p, unsigned long totalpages)
{
long points;
long adj;
if (oom_unkillable_task(p))
return LONG_MIN;
p = find_lock_task_mm(p);
if (!p)
return LONG_MIN;
/*
* Do not even consider tasks which are explicitly marked oom
* unkillable or have been already oom reaped or the are in
* the middle of vfork
*/
adj = (long)p->signal->oom_score_adj;
if (adj == OOM_SCORE_ADJ_MIN ||
test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
in_vfork(p)) {
task_unlock(p);
return LONG_MIN;
}
/*
* The baseline for the badness score is the proportion of RAM that each
* task's rss, pagetable and swap space use.
*/
points = get_mm_rss(p->mm) + get_mm_counter(p->mm, MM_SWAPENTS) +
mm_pgtables_bytes(p->mm) / PAGE_SIZE;
task_unlock(p);
/* Normalize to oom_score_adj units */
adj *= totalpages / 1000;
points += adj;
return points;
}
static const char * const oom_constraint_text[] = {
[CONSTRAINT_NONE] = "CONSTRAINT_NONE",
[CONSTRAINT_CPUSET] = "CONSTRAINT_CPUSET",
[CONSTRAINT_MEMORY_POLICY] = "CONSTRAINT_MEMORY_POLICY",
[CONSTRAINT_MEMCG] = "CONSTRAINT_MEMCG",
};
/*
* Determine the type of allocation constraint.
*/
static enum oom_constraint constrained_alloc(struct oom_control *oc)
{
struct zone *zone;
struct zoneref *z;
enum zone_type highest_zoneidx = gfp_zone(oc->gfp_mask);
bool cpuset_limited = false;
int nid;
if (is_memcg_oom(oc)) {
oc->totalpages = mem_cgroup_get_max(oc->memcg) ?: 1;
return CONSTRAINT_MEMCG;
}
/* Default to all available memory */
oc->totalpages = totalram_pages() + total_swap_pages;
if (!IS_ENABLED(CONFIG_NUMA))
return CONSTRAINT_NONE;
if (!oc->zonelist)
return CONSTRAINT_NONE;
/*
* Reach here only when __GFP_NOFAIL is used. So, we should avoid
* to kill current.We have to random task kill in this case.
* Hopefully, CONSTRAINT_THISNODE...but no way to handle it, now.
*/
if (oc->gfp_mask & __GFP_THISNODE)
return CONSTRAINT_NONE;
/*
* This is not a __GFP_THISNODE allocation, so a truncated nodemask in
* the page allocator means a mempolicy is in effect. Cpuset policy
* is enforced in get_page_from_freelist().
*/
if (oc->nodemask &&
!nodes_subset(node_states[N_MEMORY], *oc->nodemask)) {
oc->totalpages = total_swap_pages;
for_each_node_mask(nid, *oc->nodemask)
oc->totalpages += node_present_pages(nid);
return CONSTRAINT_MEMORY_POLICY;
}
/* Check this allocation failure is caused by cpuset's wall function */
for_each_zone_zonelist_nodemask(zone, z, oc->zonelist,
highest_zoneidx, oc->nodemask)
if (!cpuset_zone_allowed(zone, oc->gfp_mask))
cpuset_limited = true;
if (cpuset_limited) {
oc->totalpages = total_swap_pages;
for_each_node_mask(nid, cpuset_current_mems_allowed)
oc->totalpages += node_present_pages(nid);
return CONSTRAINT_CPUSET;
}
return CONSTRAINT_NONE;
}
static int oom_evaluate_task(struct task_struct *task, void *arg)
{
struct oom_control *oc = arg;
long points;
if (oom_unkillable_task(task))
goto next;
/* p may not have freeable memory in nodemask */
if (!is_memcg_oom(oc) && !oom_cpuset_eligible(task, oc))
goto next;
/*
* This task already has access to memory reserves and is being killed.
* Don't allow any other task to have access to the reserves unless
* the task has MMF_OOM_SKIP because chances that it would release
* any memory is quite low.
*/
if (!is_sysrq_oom(oc) && tsk_is_oom_victim(task)) {
if (test_bit(MMF_OOM_SKIP, &task->signal->oom_mm->flags))
goto next;
goto abort;
}
/*
* If task is allocating a lot of memory and has been marked to be
* killed first if it triggers an oom, then select it.
*/
if (oom_task_origin(task)) {
points = LONG_MAX;
goto select;
}
points = oom_badness(task, oc->totalpages);
if (points == LONG_MIN || points < oc->chosen_points)
goto next;
select:
if (oc->chosen)
put_task_struct(oc->chosen);
get_task_struct(task);
oc->chosen = task;
oc->chosen_points = points;
next:
return 0;
abort:
if (oc->chosen)
put_task_struct(oc->chosen);
oc->chosen = (void *)-1UL;
return 1;
}
/*
* Simple selection loop. We choose the process with the highest number of
* 'points'. In case scan was aborted, oc->chosen is set to -1.
*/
static void select_bad_process(struct oom_control *oc)
{
oc->chosen_points = LONG_MIN;
if (is_memcg_oom(oc))
mem_cgroup_scan_tasks(oc->memcg, oom_evaluate_task, oc);
else {
struct task_struct *p;
rcu_read_lock();
for_each_process(p)
if (oom_evaluate_task(p, oc))
break;
rcu_read_unlock();
}
}
static int dump_task(struct task_struct *p, void *arg)
{
struct oom_control *oc = arg;
struct task_struct *task;
if (oom_unkillable_task(p))
return 0;
/* p may not have freeable memory in nodemask */
if (!is_memcg_oom(oc) && !oom_cpuset_eligible(p, oc))
return 0;
task = find_lock_task_mm(p);
if (!task) {
/*
* All of p's threads have already detached their mm's. There's
* no need to report them; they can't be oom killed anyway.
*/
return 0;
}
pr_info("[%7d] %5d %5d %8lu %8lu %8ld %8lu %5hd %s\n",
task->pid, from_kuid(&init_user_ns, task_uid(task)),
task->tgid, task->mm->total_vm, get_mm_rss(task->mm),
mm_pgtables_bytes(task->mm),
get_mm_counter(task->mm, MM_SWAPENTS),
task->signal->oom_score_adj, task->comm);
task_unlock(task);
return 0;
}
/**
* dump_tasks - dump current memory state of all system tasks
* @oc: pointer to struct oom_control
*
* Dumps the current memory state of all eligible tasks. Tasks not in the same
* memcg, not in the same cpuset, or bound to a disjoint set of mempolicy nodes
* are not shown.
* State information includes task's pid, uid, tgid, vm size, rss,
* pgtables_bytes, swapents, oom_score_adj value, and name.
*/
static void dump_tasks(struct oom_control *oc)
{
pr_info("Tasks state (memory values in pages):\n");
pr_info("[ pid ] uid tgid total_vm rss pgtables_bytes swapents oom_score_adj name\n");
if (is_memcg_oom(oc))
mem_cgroup_scan_tasks(oc->memcg, dump_task, oc);
else {
struct task_struct *p;
rcu_read_lock();
for_each_process(p)
dump_task(p, oc);
rcu_read_unlock();
}
}
static void dump_oom_summary(struct oom_control *oc, struct task_struct *victim)
{
/* one line summary of the oom killer context. */
pr_info("oom-kill:constraint=%s,nodemask=%*pbl",
oom_constraint_text[oc->constraint],
nodemask_pr_args(oc->nodemask));
cpuset_print_current_mems_allowed();
mem_cgroup_print_oom_context(oc->memcg, victim);
pr_cont(",task=%s,pid=%d,uid=%d\n", victim->comm, victim->pid,
from_kuid(&init_user_ns, task_uid(victim)));
}
static void dump_header(struct oom_control *oc, struct task_struct *p)
{
pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), order=%d, oom_score_adj=%hd\n",
current->comm, oc->gfp_mask, &oc->gfp_mask, oc->order,
current->signal->oom_score_adj);
if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
pr_warn("COMPACTION is disabled!!!\n");
dump_stack();
if (is_memcg_oom(oc))
mem_cgroup_print_oom_meminfo(oc->memcg);
else {
__show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask, gfp_zone(oc->gfp_mask));
if (should_dump_unreclaim_slab())
dump_unreclaimable_slab();
}
if (sysctl_oom_dump_tasks)
dump_tasks(oc);
if (p)
dump_oom_summary(oc, p);
}
/*
* Number of OOM victims in flight
*/
static atomic_t oom_victims = ATOMIC_INIT(0);
static DECLARE_WAIT_QUEUE_HEAD(oom_victims_wait);
static bool oom_killer_disabled __read_mostly;
#define K(x) ((x) << (PAGE_SHIFT-10))
/*
* task->mm can be NULL if the task is the exited group leader. So to
* determine whether the task is using a particular mm, we examine all the
* task's threads: if one of those is using this mm then this task was also
* using it.
*/
bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
{
struct task_struct *t;
for_each_thread(p, t) {
struct mm_struct *t_mm = READ_ONCE(t->mm);
if (t_mm)
return t_mm == mm;
}
return false;
}
#ifdef CONFIG_MMU
/*
* OOM Reaper kernel thread which tries to reap the memory used by the OOM
* victim (if that is possible) to help the OOM killer to move on.
*/
static struct task_struct *oom_reaper_th;
static DECLARE_WAIT_QUEUE_HEAD(oom_reaper_wait);
static struct task_struct *oom_reaper_list;
static DEFINE_SPINLOCK(oom_reaper_lock);
static bool __oom_reap_task_mm(struct mm_struct *mm)
{
struct vm_area_struct *vma;
bool ret = true;
VMA_ITERATOR(vmi, mm, 0);
/*
* Tell all users of get_user/copy_from_user etc... that the content
* is no longer stable. No barriers really needed because unmapping
* should imply barriers already and the reader would hit a page fault
* if it stumbled over a reaped memory.
*/
set_bit(MMF_UNSTABLE, &mm->flags);
for_each_vma(vmi, vma) {
if (vma->vm_flags & (VM_HUGETLB|VM_PFNMAP))
continue;
/*
* Only anonymous pages have a good chance to be dropped
* without additional steps which we cannot afford as we
* are OOM already.
*
* We do not even care about fs backed pages because all
* which are reclaimable have already been reclaimed and
* we do not want to block exit_mmap by keeping mm ref
* count elevated without a good reason.
*/
if (vma_is_anonymous(vma) || !(vma->vm_flags & VM_SHARED)) {
struct mmu_notifier_range range;
struct mmu_gather tlb;
mmu_notifier_range_init(&range, MMU_NOTIFY_UNMAP, 0,
vma, mm, vma->vm_start,
vma->vm_end);
tlb_gather_mmu(&tlb, mm);
if (mmu_notifier_invalidate_range_start_nonblock(&range)) {
tlb_finish_mmu(&tlb);
ret = false;
continue;
}
unmap_page_range(&tlb, vma, range.start, range.end, NULL);
mmu_notifier_invalidate_range_end(&range);
tlb_finish_mmu(&tlb);
}
}
return ret;
}
/*
* Reaps the address space of the give task.
*
* Returns true on success and false if none or part of the address space
* has been reclaimed and the caller should retry later.
*/
static bool oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
{
bool ret = true;
if (!mmap_read_trylock(mm)) {
trace_skip_task_reaping(tsk->pid);
return false;
}
/*
* MMF_OOM_SKIP is set by exit_mmap when the OOM reaper can't
* work on the mm anymore. The check for MMF_OOM_SKIP must run
* under mmap_lock for reading because it serializes against the
* mmap_write_lock();mmap_write_unlock() cycle in exit_mmap().
*/
if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
trace_skip_task_reaping(tsk->pid);
goto out_unlock;
}
trace_start_task_reaping(tsk->pid);
/* failed to reap part of the address space. Try again later */
ret = __oom_reap_task_mm(mm);
if (!ret)
goto out_finish;
pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
task_pid_nr(tsk), tsk->comm,
K(get_mm_counter(mm, MM_ANONPAGES)),
K(get_mm_counter(mm, MM_FILEPAGES)),
K(get_mm_counter(mm, MM_SHMEMPAGES)));
out_finish:
trace_finish_task_reaping(tsk->pid);
out_unlock:
mmap_read_unlock(mm);
return ret;
}
#define MAX_OOM_REAP_RETRIES 10
static void oom_reap_task(struct task_struct *tsk)
{
int attempts = 0;
struct mm_struct *mm = tsk->signal->oom_mm;
/* Retry the mmap_read_trylock(mm) a few times */
while (attempts++ < MAX_OOM_REAP_RETRIES && !oom_reap_task_mm(tsk, mm))
schedule_timeout_idle(HZ/10);
if (attempts <= MAX_OOM_REAP_RETRIES ||
test_bit(MMF_OOM_SKIP, &mm->flags))
goto done;
pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
task_pid_nr(tsk), tsk->comm);
sched_show_task(tsk);
debug_show_all_locks();
done:
tsk->oom_reaper_list = NULL;
/*
* Hide this mm from OOM killer because it has been either reaped or
* somebody can't call mmap_write_unlock(mm).
*/
set_bit(MMF_OOM_SKIP, &mm->flags);
/* Drop a reference taken by queue_oom_reaper */
put_task_struct(tsk);
}
static int oom_reaper(void *unused)
{
set_freezable();
while (true) {
struct task_struct *tsk = NULL;
wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
spin_lock_irq(&oom_reaper_lock);
if (oom_reaper_list != NULL) {
tsk = oom_reaper_list;
oom_reaper_list = tsk->oom_reaper_list;
}
spin_unlock_irq(&oom_reaper_lock);
if (tsk)
oom_reap_task(tsk);
}
return 0;
}
static void wake_oom_reaper(struct timer_list *timer)
{
struct task_struct *tsk = container_of(timer, struct task_struct,
oom_reaper_timer);
struct mm_struct *mm = tsk->signal->oom_mm;
unsigned long flags;
/* The victim managed to terminate on its own - see exit_mmap */
if (test_bit(MMF_OOM_SKIP, &mm->flags)) {
put_task_struct(tsk);
return;
}
spin_lock_irqsave(&oom_reaper_lock, flags);
tsk->oom_reaper_list = oom_reaper_list;
oom_reaper_list = tsk;
spin_unlock_irqrestore(&oom_reaper_lock, flags);
trace_wake_reaper(tsk->pid);
wake_up(&oom_reaper_wait);
}
/*
* Give the OOM victim time to exit naturally before invoking the oom_reaping.
* The timers timeout is arbitrary... the longer it is, the longer the worst
* case scenario for the OOM can take. If it is too small, the oom_reaper can
* get in the way and release resources needed by the process exit path.
* e.g. The futex robust list can sit in Anon|Private memory that gets reaped
* before the exit path is able to wake the futex waiters.
*/
#define OOM_REAPER_DELAY (2*HZ)
static void queue_oom_reaper(struct task_struct *tsk)
{
/* mm is already queued? */
if (test_and_set_bit(MMF_OOM_REAP_QUEUED, &tsk->signal->oom_mm->flags))
return;
get_task_struct(tsk);
timer_setup(&tsk->oom_reaper_timer, wake_oom_reaper, 0);
tsk->oom_reaper_timer.expires = jiffies + OOM_REAPER_DELAY;
add_timer(&tsk->oom_reaper_timer);
}
#ifdef CONFIG_SYSCTL
static struct ctl_table vm_oom_kill_table[] = {
{
.procname = "panic_on_oom",
.data = &sysctl_panic_on_oom,
.maxlen = sizeof(sysctl_panic_on_oom),
.mode = 0644,
.proc_handler = proc_dointvec_minmax,
.extra1 = SYSCTL_ZERO,
.extra2 = SYSCTL_TWO,
},
{
.procname = "oom_kill_allocating_task",
.data = &sysctl_oom_kill_allocating_task,
.maxlen = sizeof(sysctl_oom_kill_allocating_task),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{
.procname = "oom_dump_tasks",
.data = &sysctl_oom_dump_tasks,
.maxlen = sizeof(sysctl_oom_dump_tasks),
.mode = 0644,
.proc_handler = proc_dointvec,
},
{}
};
#endif
static int __init oom_init(void)
{
oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
#ifdef CONFIG_SYSCTL
register_sysctl_init("vm", vm_oom_kill_table);
#endif
return 0;
}
subsys_initcall(oom_init)
#else
static inline void queue_oom_reaper(struct task_struct *tsk)
{
}
#endif /* CONFIG_MMU */
/**
* mark_oom_victim - mark the given task as OOM victim
* @tsk: task to mark
*
* Has to be called with oom_lock held and never after
* oom has been disabled already.
*
* tsk->mm has to be non NULL and caller has to guarantee it is stable (either
* under task_lock or operate on the current).
*/
static void mark_oom_victim(struct task_struct *tsk)
{
struct mm_struct *mm = tsk->mm;
WARN_ON(oom_killer_disabled);
/* OOM killer might race with memcg OOM */
if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
return;
/* oom_mm is bound to the signal struct life time. */
if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
mmgrab(tsk->signal->oom_mm);
/*
* Make sure that the task is woken up from uninterruptible sleep
* if it is frozen because OOM killer wouldn't be able to free
* any memory and livelock. freezing_slow_path will tell the freezer
* that TIF_MEMDIE tasks should be ignored.
*/
__thaw_task(tsk);
atomic_inc(&oom_victims);
trace_mark_victim(tsk->pid);
}
/**
* exit_oom_victim - note the exit of an OOM victim
*/
void exit_oom_victim(void)
{
clear_thread_flag(TIF_MEMDIE);
if (!atomic_dec_return(&oom_victims))
wake_up_all(&oom_victims_wait);
}
/**
* oom_killer_enable - enable OOM killer
*/
void oom_killer_enable(void)
{
oom_killer_disabled = false;
pr_info("OOM killer enabled.\n");
}
/**
* oom_killer_disable - disable OOM killer
* @timeout: maximum timeout to wait for oom victims in jiffies
*
* Forces all page allocations to fail rather than trigger OOM killer.
* Will block and wait until all OOM victims are killed or the given
* timeout expires.
*
* The function cannot be called when there are runnable user tasks because
* the userspace would see unexpected allocation failures as a result. Any
* new usage of this function should be consulted with MM people.
*
* Returns true if successful and false if the OOM killer cannot be
* disabled.
*/
bool oom_killer_disable(signed long timeout)
{
signed long ret;
/*
* Make sure to not race with an ongoing OOM killer. Check that the
* current is not killed (possibly due to sharing the victim's memory).
*/
if (mutex_lock_killable(&oom_lock))
return false;
oom_killer_disabled = true;
mutex_unlock(&oom_lock);
ret = wait_event_interruptible_timeout(oom_victims_wait,
!atomic_read(&oom_victims), timeout);
if (ret <= 0) {
oom_killer_enable();
return false;
}
pr_info("OOM killer disabled.\n");
return true;
}
static inline bool __task_will_free_mem(struct task_struct *task)
{
struct signal_struct *sig = task->signal;
/*
* A coredumping process may sleep for an extended period in
* coredump_task_exit(), so the oom killer cannot assume that
* the process will promptly exit and release memory.
*/
if (sig->core_state)
return false;
if (sig->flags & SIGNAL_GROUP_EXIT)
return true;
if (thread_group_empty(task) && (task->flags & PF_EXITING))
return true;
return false;
}
/*
* Checks whether the given task is dying or exiting and likely to
* release its address space. This means that all threads and processes
* sharing the same mm have to be killed or exiting.
* Caller has to make sure that task->mm is stable (hold task_lock or
* it operates on the current).
*/
static bool task_will_free_mem(struct task_struct *task)
{
struct mm_struct *mm = task->mm;
struct task_struct *p;
bool ret = true;
/*
* Skip tasks without mm because it might have passed its exit_mm and
* exit_oom_victim. oom_reaper could have rescued that but do not rely
* on that for now. We can consider find_lock_task_mm in future.
*/
if (!mm)
return false;
if (!__task_will_free_mem(task))
return false;
/*
* This task has already been drained by the oom reaper so there are
* only small chances it will free some more
*/
if (test_bit(MMF_OOM_SKIP, &mm->flags))
return false;
if (atomic_read(&mm->mm_users) <= 1)
return true;
/*
* Make sure that all tasks which share the mm with the given tasks
* are dying as well to make sure that a) nobody pins its mm and
* b) the task is also reapable by the oom reaper.
*/
rcu_read_lock();
for_each_process(p) {
if (!process_shares_mm(p, mm))
continue;
if (same_thread_group(task, p))
continue;
ret = __task_will_free_mem(p);
if (!ret)
break;
}
rcu_read_unlock();
return ret;
}
static void __oom_kill_process(struct task_struct *victim, const char *message)
{
struct task_struct *p;
struct mm_struct *mm;
bool can_oom_reap = true;
p = find_lock_task_mm(victim);
if (!p) {
pr_info("%s: OOM victim %d (%s) is already exiting. Skip killing the task\n",
message, task_pid_nr(victim), victim->comm);
put_task_struct(victim);
return;
} else if (victim != p) {
get_task_struct(p);
put_task_struct(victim);
victim = p;
}
/* Get a reference to safely compare mm after task_unlock(victim) */
mm = victim->mm;
mmgrab(mm);
/* Raise event before sending signal: task reaper must see this */
count_vm_event(OOM_KILL);
memcg_memory_event_mm(mm, MEMCG_OOM_KILL);
/*
* We should send SIGKILL before granting access to memory reserves
* in order to prevent the OOM victim from depleting the memory
* reserves from the user space under its control.
*/
do_send_sig_info(SIGKILL, SEND_SIG_PRIV, victim, PIDTYPE_TGID);
mark_oom_victim(victim);
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",
message, task_pid_nr(victim), victim->comm, K(mm->total_vm),
K(get_mm_counter(mm, MM_ANONPAGES)),
K(get_mm_counter(mm, MM_FILEPAGES)),
K(get_mm_counter(mm, MM_SHMEMPAGES)),
from_kuid(&init_user_ns, task_uid(victim)),
mm_pgtables_bytes(mm) >> 10, victim->signal->oom_score_adj);
task_unlock(victim);
/*
* Kill all user processes sharing victim->mm in other thread groups, if
* any. They don't get access to memory reserves, though, to avoid
* depletion of all memory. This prevents mm->mmap_lock livelock when an
* oom killed thread cannot exit because it requires the semaphore and
* its contended by another thread trying to allocate memory itself.
* That thread will now get access to memory reserves since it has a
* pending fatal signal.
*/
rcu_read_lock();
for_each_process(p) {
if (!process_shares_mm(p, mm))
continue;
if (same_thread_group(p, victim))
continue;
if (is_global_init(p)) {
can_oom_reap = false;
set_bit(MMF_OOM_SKIP, &mm->flags);
pr_info("oom killer %d (%s) has mm pinned by %d (%s)\n",
task_pid_nr(victim), victim->comm,
task_pid_nr(p), p->comm);
continue;
}
/*
* No kthread_use_mm() user needs to read from the userspace so
* we are ok to reap it.
*/
if (unlikely(p->flags & PF_KTHREAD))
continue;
do_send_sig_info(SIGKILL, SEND_SIG_PRIV, p, PIDTYPE_TGID);
}
rcu_read_unlock();
if (can_oom_reap)
queue_oom_reaper(victim);
mmdrop(mm);
put_task_struct(victim);
}
#undef K
/*
* Kill provided task unless it's secured by setting
* oom_score_adj to OOM_SCORE_ADJ_MIN.
*/
static int oom_kill_memcg_member(struct task_struct *task, void *message)
{
if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN &&
!is_global_init(task)) {
get_task_struct(task);
__oom_kill_process(task, message);
}
return 0;
}
static void oom_kill_process(struct oom_control *oc, const char *message)
{
struct task_struct *victim = oc->chosen;
struct mem_cgroup *oom_group;
static DEFINE_RATELIMIT_STATE(oom_rs, DEFAULT_RATELIMIT_INTERVAL,
DEFAULT_RATELIMIT_BURST);
/*
* If the task is already exiting, don't alarm the sysadmin or kill
* its children or threads, just give it access to memory reserves
* so it can die quickly
*/
task_lock(victim);
if (task_will_free_mem(victim)) {
mark_oom_victim(victim);
queue_oom_reaper(victim);
task_unlock(victim);
put_task_struct(victim);
return;
}
task_unlock(victim);
if (__ratelimit(&oom_rs))
dump_header(oc, victim);
/*
* Do we need to kill the entire memory cgroup?
* Or even one of the ancestor memory cgroups?
* Check this out before killing the victim task.
*/
oom_group = mem_cgroup_get_oom_group(victim, oc->memcg);
__oom_kill_process(victim, message);
/*
* If necessary, kill all tasks in the selected memory cgroup.
*/
if (oom_group) {
memcg_memory_event(oom_group, MEMCG_OOM_GROUP_KILL);
mem_cgroup_print_oom_group(oom_group);
mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member,
(void *)message);
mem_cgroup_put(oom_group);
}
}
/*
* Determines whether the kernel must panic because of the panic_on_oom sysctl.
*/
static void check_panic_on_oom(struct oom_control *oc)
{
if (likely(!sysctl_panic_on_oom))
return;
if (sysctl_panic_on_oom != 2) {
/*
* panic_on_oom == 1 only affects CONSTRAINT_NONE, the kernel
* does not panic for cpuset, mempolicy, or memcg allocation
* failures.
*/
if (oc->constraint != CONSTRAINT_NONE)
return;
}
/* Do not panic for oom kills triggered by sysrq */
if (is_sysrq_oom(oc))
return;
dump_header(oc, NULL);
panic("Out of memory: %s panic_on_oom is enabled\n",
sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
}
static BLOCKING_NOTIFIER_HEAD(oom_notify_list);
int register_oom_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_register(&oom_notify_list, nb);
}
EXPORT_SYMBOL_GPL(register_oom_notifier);
int unregister_oom_notifier(struct notifier_block *nb)
{
return blocking_notifier_chain_unregister(&oom_notify_list, nb);
}
EXPORT_SYMBOL_GPL(unregister_oom_notifier);
/**
* out_of_memory - kill the "best" process when we run out of memory
* @oc: pointer to struct oom_control
*
* If we run out of memory, we have the choice between either
* killing a random task (bad), letting the system crash (worse)
* OR try to be smart about which process to kill. Note that we
* don't have to be perfect here, we just have to be good.
*/
bool out_of_memory(struct oom_control *oc)
{
unsigned long freed = 0;
if (oom_killer_disabled)
return false;
if (!is_memcg_oom(oc)) {
blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
if (freed > 0 && !is_sysrq_oom(oc))
/* Got some memory back in the last second. */
return true;
}
/*
* If current has a pending SIGKILL or is exiting, then automatically
* select it. The goal is to allow it to allocate so that it may
* quickly exit and free its memory.
*/
if (task_will_free_mem(current)) {
mark_oom_victim(current);
queue_oom_reaper(current);
return true;
}
/*
* The OOM killer does not compensate for IO-less reclaim.
* pagefault_out_of_memory lost its gfp context so we have to
* make sure exclude 0 mask - all other users should have at least
* ___GFP_DIRECT_RECLAIM to get here. But mem_cgroup_oom() has to
* invoke the OOM killer even if it is a GFP_NOFS allocation.
*/
if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS) && !is_memcg_oom(oc))
return true;
/*
* Check if there were limitations on the allocation (only relevant for
* NUMA and memcg) that may require different handling.
*/
oc->constraint = constrained_alloc(oc);
if (oc->constraint != CONSTRAINT_MEMORY_POLICY)
oc->nodemask = NULL;
check_panic_on_oom(oc);
if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
current->mm && !oom_unkillable_task(current) &&
oom_cpuset_eligible(current, oc) &&
current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
get_task_struct(current);
oc->chosen = current;
oom_kill_process(oc, "Out of memory (oom_kill_allocating_task)");
return true;
}
select_bad_process(oc);
/* Found nothing?!?! */
if (!oc->chosen) {
dump_header(oc, NULL);
pr_warn("Out of memory and no killable processes...\n");
/*
* If we got here due to an actual allocation at the
* system level, we cannot survive this and will enter
* an endless loop in the allocator. Bail out now.
*/
if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
panic("System is deadlocked on memory\n");
}
if (oc->chosen && oc->chosen != (void *)-1UL)
oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
"Memory cgroup out of memory");
return !!oc->chosen;
}
/*
* The pagefault handler calls here because some allocation has failed. We have
* to take care of the memcg OOM here because this is the only safe context without
* any locks held but let the oom killer triggered from the allocation context care
* about the global OOM.
*/
void pagefault_out_of_memory(void)
{
static DEFINE_RATELIMIT_STATE(pfoom_rs, DEFAULT_RATELIMIT_INTERVAL,
DEFAULT_RATELIMIT_BURST);
if (mem_cgroup_oom_synchronize(true))
return;
if (fatal_signal_pending(current))
return;
if (__ratelimit(&pfoom_rs))
pr_warn("Huh VM_FAULT_OOM leaked out to the #PF handler. Retrying PF\n");
}
SYSCALL_DEFINE2(process_mrelease, int, pidfd, unsigned int, flags)
{
#ifdef CONFIG_MMU
struct mm_struct *mm = NULL;
struct task_struct *task;
struct task_struct *p;
unsigned int f_flags;
bool reap = false;
long ret = 0;
if (flags)
return -EINVAL;
task = pidfd_get_task(pidfd, &f_flags);
if (IS_ERR(task))
return PTR_ERR(task);
/*
* Make sure to choose a thread which still has a reference to mm
* during the group exit
*/
p = find_lock_task_mm(task);
if (!p) {
ret = -ESRCH;
goto put_task;
}
mm = p->mm;
mmgrab(mm);
if (task_will_free_mem(p))
reap = true;
else {
/* Error only if the work has not been done already */
if (!test_bit(MMF_OOM_SKIP, &mm->flags))
ret = -EINVAL;
}
task_unlock(p);
if (!reap)
goto drop_mm;
if (mmap_read_lock_killable(mm)) {
ret = -EINTR;
goto drop_mm;
}
/*
* Check MMF_OOM_SKIP again under mmap_read_lock protection to ensure
* possible change in exit_mmap is seen
*/
if (!test_bit(MMF_OOM_SKIP, &mm->flags) && !__oom_reap_task_mm(mm))
ret = -EAGAIN;
mmap_read_unlock(mm);
drop_mm:
mmdrop(mm);
put_task:
put_task_struct(task);
return ret;
#else
return -ENOSYS;
#endif /* CONFIG_MMU */
}