linux/mm/oom_kill.c
Linus Torvalds ba9f6f8954 Merge branch 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace
Pull siginfo updates from Eric Biederman:
 "I have been slowly sorting out siginfo and this is the culmination of
  that work.

  The primary result is in several ways the signal infrastructure has
  been made less error prone. The code has been updated so that manually
  specifying SEND_SIG_FORCED is never necessary. The conversion to the
  new siginfo sending functions is now complete, which makes it
  difficult to send a signal without filling in the proper siginfo
  fields.

  At the tail end of the patchset comes the optimization of decreasing
  the size of struct siginfo in the kernel from 128 bytes to about 48
  bytes on 64bit. The fundamental observation that enables this is by
  definition none of the known ways to use struct siginfo uses the extra
  bytes.

  This comes at the cost of a small user space observable difference.
  For the rare case of siginfo being injected into the kernel only what
  can be copied into kernel_siginfo is delivered to the destination, the
  rest of the bytes are set to 0. For cases where the signal and the
  si_code are known this is safe, because we know those bytes are not
  used. For cases where the signal and si_code combination is unknown
  the bits that won't fit into struct kernel_siginfo are tested to
  verify they are zero, and the send fails if they are not.

  I made an extensive search through userspace code and I could not find
  anything that would break because of the above change. If it turns out
  I did break something it will take just the revert of a single change
  to restore kernel_siginfo to the same size as userspace siginfo.

  Testing did reveal dependencies on preferring the signo passed to
  sigqueueinfo over si->signo, so bit the bullet and added the
  complexity necessary to handle that case.

  Testing also revealed bad things can happen if a negative signal
  number is passed into the system calls. Something no sane application
  will do but something a malicious program or a fuzzer might do. So I
  have fixed the code that performs the bounds checks to ensure negative
  signal numbers are handled"

* 'siginfo-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (80 commits)
  signal: Guard against negative signal numbers in copy_siginfo_from_user32
  signal: Guard against negative signal numbers in copy_siginfo_from_user
  signal: In sigqueueinfo prefer sig not si_signo
  signal: Use a smaller struct siginfo in the kernel
  signal: Distinguish between kernel_siginfo and siginfo
  signal: Introduce copy_siginfo_from_user and use it's return value
  signal: Remove the need for __ARCH_SI_PREABLE_SIZE and SI_PAD_SIZE
  signal: Fail sigqueueinfo if si_signo != sig
  signal/sparc: Move EMT_TAGOVF into the generic siginfo.h
  signal/unicore32: Use force_sig_fault where appropriate
  signal/unicore32: Generate siginfo in ucs32_notify_die
  signal/unicore32: Use send_sig_fault where appropriate
  signal/arc: Use force_sig_fault where appropriate
  signal/arc: Push siginfo generation into unhandled_exception
  signal/ia64: Use force_sig_fault where appropriate
  signal/ia64: Use the force_sig(SIGSEGV,...) in ia64_rt_sigreturn
  signal/ia64: Use the generic force_sigsegv in setup_frame
  signal/arm/kvm: Use send_sig_mceerr
  signal/arm: Use send_sig_fault where appropriate
  signal/arm: Use force_sig_fault where appropriate
  ...
2018-10-24 11:22:39 +01:00

1148 lines
31 KiB
C

/*
* 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/swap.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>
int sysctl_panic_on_oom;
int sysctl_oom_kill_allocating_task;
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);
#ifdef CONFIG_NUMA
/**
* has_intersects_mems_allowed() - check task eligiblity for kill
* @start: task struct of which task to consider
* @mask: nodemask passed to page allocator for mempolicy ooms
*
* 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.
*/
static bool has_intersects_mems_allowed(struct task_struct *start,
const nodemask_t *mask)
{
struct task_struct *tsk;
bool ret = false;
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_nodemask_intersects(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 has_intersects_mems_allowed(struct task_struct *tsk,
const nodemask_t *mask)
{
return true;
}
#endif /* CONFIG_NUMA */
/*
* The process p may have detached its own ->mm while exiting or through
* 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;
}
static inline bool is_memcg_oom(struct oom_control *oc)
{
return oc->memcg != NULL;
}
/* return true if the task is not adequate as candidate victim task. */
static bool oom_unkillable_task(struct task_struct *p,
struct mem_cgroup *memcg, const nodemask_t *nodemask)
{
if (is_global_init(p))
return true;
if (p->flags & PF_KTHREAD)
return true;
/* When mem_cgroup_out_of_memory() and p is not member of the group */
if (memcg && !task_in_mem_cgroup(p, memcg))
return true;
/* p may not have freeable memory in nodemask */
if (!has_intersects_mems_allowed(p, nodemask))
return true;
return false;
}
/*
* Print out unreclaimble slabs info when unreclaimable slabs amount is greater
* than all user memory (LRU pages)
*/
static bool is_dump_unreclaim_slabs(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(NR_SLAB_UNRECLAIMABLE) > 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
* @memcg: task's memory controller, if constrained
* @nodemask: nodemask passed to page allocator for mempolicy ooms
*
* 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.
*/
unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
const nodemask_t *nodemask, unsigned long totalpages)
{
long points;
long adj;
if (oom_unkillable_task(p, memcg, nodemask))
return 0;
p = find_lock_task_mm(p);
if (!p)
return 0;
/*
* 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 0;
}
/*
* 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;
/*
* Never return 0 for an eligible task regardless of the root bonus and
* oom_score_adj (oom_score_adj can't be OOM_SCORE_ADJ_MIN here).
*/
return points > 0 ? points : 1;
}
enum oom_constraint {
CONSTRAINT_NONE,
CONSTRAINT_CPUSET,
CONSTRAINT_MEMORY_POLICY,
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 high_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_spanned_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,
high_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_spanned_pages(nid);
return CONSTRAINT_CPUSET;
}
return CONSTRAINT_NONE;
}
static int oom_evaluate_task(struct task_struct *task, void *arg)
{
struct oom_control *oc = arg;
unsigned long points;
if (oom_unkillable_task(task, NULL, oc->nodemask))
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 = ULONG_MAX;
goto select;
}
points = oom_badness(task, NULL, oc->nodemask, oc->totalpages);
if (!points || points < oc->chosen_points)
goto next;
/* Prefer thread group leaders for display purposes */
if (points == oc->chosen_points && thread_group_leader(oc->chosen))
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)
{
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();
}
oc->chosen_points = oc->chosen_points * 1000 / oc->totalpages;
}
/**
* dump_tasks - dump current memory state of all system tasks
* @memcg: current's memory controller, if constrained
* @nodemask: nodemask passed to page allocator for mempolicy ooms
*
* 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 mem_cgroup *memcg, const nodemask_t *nodemask)
{
struct task_struct *p;
struct task_struct *task;
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");
rcu_read_lock();
for_each_process(p) {
if (oom_unkillable_task(p, memcg, nodemask))
continue;
task = find_lock_task_mm(p);
if (!task) {
/*
* This is a kthread or 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.
*/
continue;
}
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);
}
rcu_read_unlock();
}
static void dump_header(struct oom_control *oc, struct task_struct *p)
{
pr_warn("%s invoked oom-killer: gfp_mask=%#x(%pGg), nodemask=%*pbl, order=%d, oom_score_adj=%hd\n",
current->comm, oc->gfp_mask, &oc->gfp_mask,
nodemask_pr_args(oc->nodemask), oc->order,
current->signal->oom_score_adj);
if (!IS_ENABLED(CONFIG_COMPACTION) && oc->order)
pr_warn("COMPACTION is disabled!!!\n");
cpuset_print_current_mems_allowed();
dump_stack();
if (is_memcg_oom(oc))
mem_cgroup_print_oom_info(oc->memcg, p);
else {
show_mem(SHOW_MEM_FILTER_NODES, oc->nodemask);
if (is_dump_unreclaim_slabs())
dump_unreclaimable_slab();
}
if (sysctl_oom_dump_tasks)
dump_tasks(oc->memcg, oc->nodemask);
}
/*
* 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);
bool __oom_reap_task_mm(struct mm_struct *mm)
{
struct vm_area_struct *vma;
bool ret = true;
/*
* 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 (vma = mm->mmap ; vma; vma = vma->vm_next) {
if (!can_madv_dontneed_vma(vma))
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)) {
const unsigned long start = vma->vm_start;
const unsigned long end = vma->vm_end;
struct mmu_gather tlb;
tlb_gather_mmu(&tlb, mm, start, end);
if (mmu_notifier_invalidate_range_start_nonblock(mm, start, end)) {
tlb_finish_mmu(&tlb, start, end);
ret = false;
continue;
}
unmap_page_range(&tlb, vma, start, end, NULL);
mmu_notifier_invalidate_range_end(mm, start, end);
tlb_finish_mmu(&tlb, start, end);
}
}
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 (!down_read_trylock(&mm->mmap_sem)) {
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_sem for reading because it serializes against the
* down_write();up_write() 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:
up_read(&mm->mmap_sem);
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 down_read_trylock(mmap_sem) 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);
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 up_write(mmap_sem).
*/
set_bit(MMF_OOM_SKIP, &mm->flags);
/* Drop a reference taken by wake_oom_reaper */
put_task_struct(tsk);
}
static int oom_reaper(void *unused)
{
while (true) {
struct task_struct *tsk = NULL;
wait_event_freezable(oom_reaper_wait, oom_reaper_list != NULL);
spin_lock(&oom_reaper_lock);
if (oom_reaper_list != NULL) {
tsk = oom_reaper_list;
oom_reaper_list = tsk->oom_reaper_list;
}
spin_unlock(&oom_reaper_lock);
if (tsk)
oom_reap_task(tsk);
}
return 0;
}
static void wake_oom_reaper(struct task_struct *tsk)
{
/* tsk is already queued? */
if (tsk == oom_reaper_list || tsk->oom_reaper_list)
return;
get_task_struct(tsk);
spin_lock(&oom_reaper_lock);
tsk->oom_reaper_list = oom_reaper_list;
oom_reaper_list = tsk;
spin_unlock(&oom_reaper_lock);
trace_wake_reaper(tsk->pid);
wake_up(&oom_reaper_wait);
}
static int __init oom_init(void)
{
oom_reaper_th = kthread_run(oom_reaper, NULL, "oom_reaper");
return 0;
}
subsys_initcall(oom_init)
#else
static inline void wake_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);
set_bit(MMF_OOM_VICTIM, &mm->flags);
}
/*
* 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 exit_mm(),
* so the oom killer cannot assume that the process will promptly exit
* and release memory.
*/
if (sig->flags & SIGNAL_GROUP_COREDUMP)
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)
{
struct task_struct *p;
struct mm_struct *mm;
bool can_oom_reap = true;
p = find_lock_task_mm(victim);
if (!p) {
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("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
K(get_mm_counter(victim->mm, MM_ANONPAGES)),
K(get_mm_counter(victim->mm, MM_FILEPAGES)),
K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
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_sem 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 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)
wake_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 *unused)
{
if (task->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
get_task_struct(task);
__oom_kill_process(task);
}
return 0;
}
static void oom_kill_process(struct oom_control *oc, const char *message)
{
struct task_struct *p = oc->chosen;
unsigned int points = oc->chosen_points;
struct task_struct *victim = p;
struct task_struct *child;
struct task_struct *t;
struct mem_cgroup *oom_group;
unsigned int victim_points = 0;
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(p);
if (task_will_free_mem(p)) {
mark_oom_victim(p);
wake_oom_reaper(p);
task_unlock(p);
put_task_struct(p);
return;
}
task_unlock(p);
if (__ratelimit(&oom_rs))
dump_header(oc, p);
pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
message, task_pid_nr(p), p->comm, points);
/*
* If any of p's children has a different mm and is eligible for kill,
* the one with the highest oom_badness() score is sacrificed for its
* parent. This attempts to lose the minimal amount of work done while
* still freeing memory.
*/
read_lock(&tasklist_lock);
for_each_thread(p, t) {
list_for_each_entry(child, &t->children, sibling) {
unsigned int child_points;
if (process_shares_mm(child, p->mm))
continue;
/*
* oom_badness() returns 0 if the thread is unkillable
*/
child_points = oom_badness(child,
oc->memcg, oc->nodemask, oc->totalpages);
if (child_points > victim_points) {
put_task_struct(victim);
victim = child;
victim_points = child_points;
get_task_struct(victim);
}
}
}
read_unlock(&tasklist_lock);
/*
* 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);
/*
* If necessary, kill all tasks in the selected memory cgroup.
*/
if (oom_group) {
mem_cgroup_print_oom_group(oom_group);
mem_cgroup_scan_tasks(oom_group, oom_kill_memcg_member, NULL);
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,
enum oom_constraint constraint)
{
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 (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;
enum oom_constraint constraint = CONSTRAINT_NONE;
if (oom_killer_disabled)
return false;
if (!is_memcg_oom(oc)) {
blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
if (freed > 0)
/* 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);
wake_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.
*/
if (oc->gfp_mask && !(oc->gfp_mask & __GFP_FS))
return true;
/*
* Check if there were limitations on the allocation (only relevant for
* NUMA and memcg) that may require different handling.
*/
constraint = constrained_alloc(oc);
if (constraint != CONSTRAINT_MEMORY_POLICY)
oc->nodemask = NULL;
check_panic_on_oom(oc, constraint);
if (!is_memcg_oom(oc) && sysctl_oom_kill_allocating_task &&
current->mm && !oom_unkillable_task(current, NULL, oc->nodemask) &&
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 it is out of memory, so kill a
* memory-hogging task. If oom_lock is held by somebody else, a parallel oom
* killing is already in progress so do nothing.
*/
void pagefault_out_of_memory(void)
{
struct oom_control oc = {
.zonelist = NULL,
.nodemask = NULL,
.memcg = NULL,
.gfp_mask = 0,
.order = 0,
};
if (mem_cgroup_oom_synchronize(true))
return;
if (!mutex_trylock(&oom_lock))
return;
out_of_memory(&oc);
mutex_unlock(&oom_lock);
}