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/*
* 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/swap.h>
#include <linux/timex.h>
#include <linux/jiffies.h>
#include <linux/cpuset.h>
#include <linux/module.h>
#include <linux/notifier.h>
#include <linux/memcontrol.h>
#include <linux/mempolicy.h>
#include <linux/security.h>
#include <linux/ptrace.h>
int sysctl_panic_on_oom;
int sysctl_oom_kill_allocating_task;
int sysctl_oom_dump_tasks = 1;
static DEFINE_SPINLOCK(zone_scan_lock);
#ifdef CONFIG_NUMA
/**
* has_intersects_mems_allowed() - check task eligiblity for kill
* @tsk: 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 *tsk,
const nodemask_t *mask)
{
struct task_struct *start = tsk;
do {
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.
*/
if (mempolicy_nodemask_intersects(tsk, mask))
return true;
} else {
/*
* This is not a mempolicy constrained oom, so only
* check the mems of tsk's cpuset.
*/
if (cpuset_mems_allowed_intersects(current, tsk))
return true;
}
} while_each_thread(start, tsk);
return false;
}
#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 = p;
do {
task_lock(t);
if (likely(t->mm))
return t;
task_unlock(t);
} while_each_thread(p, t);
return NULL;
}
/* return true if the task is not adequate as candidate victim task. */
static bool oom_unkillable_task(struct task_struct *p,
const struct mem_cgroup *mem, 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 (mem && !task_in_mem_cgroup(p, mem))
return true;
/* p may not have freeable memory in nodemask */
if (!has_intersects_mems_allowed(p, nodemask))
return true;
return false;
}
/**
* 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.
*/
unsigned int oom_badness(struct task_struct *p, struct mem_cgroup *mem,
const nodemask_t *nodemask, unsigned long totalpages)
{
int points;
if (oom_unkillable_task(p, mem, nodemask))
return 0;
p = find_lock_task_mm(p);
if (!p)
return 0;
/*
* Shortcut check for a thread sharing p->mm that is OOM_SCORE_ADJ_MIN
* so the entire heuristic doesn't need to be executed for something
* that cannot be killed.
*/
if (atomic_read(&p->mm->oom_disable_count)) {
task_unlock(p);
return 0;
}
/*
* When the PF_OOM_ORIGIN bit is set, it indicates the task should have
* priority for oom killing.
*/
if (p->flags & PF_OOM_ORIGIN) {
task_unlock(p);
return 1000;
}
/*
* The memory controller may have a limit of 0 bytes, so avoid a divide
* by zero, if necessary.
*/
if (!totalpages)
totalpages = 1;
/*
* 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) + p->mm->nr_ptes;
points += get_mm_counter(p->mm, MM_SWAPENTS);
points *= 1000;
points /= totalpages;
task_unlock(p);
/*
* Root processes get 3% bonus, just like the __vm_enough_memory()
* implementation used by LSMs.
*/
if (has_capability_noaudit(p, CAP_SYS_ADMIN))
points -= 30;
/*
* /proc/pid/oom_score_adj ranges from -1000 to +1000 such that it may
* either completely disable oom killing or always prefer a certain
* task.
*/
points += p->signal->oom_score_adj;
/*
* Never return 0 for an eligible task that may be killed since it's
* possible that no single user task uses more than 0.1% of memory and
* no single admin tasks uses more than 3.0%.
*/
if (points <= 0)
return 1;
return (points < 1000) ? points : 1000;
}
/*
* Determine the type of allocation constraint.
*/
#ifdef CONFIG_NUMA
static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
gfp_t gfp_mask, nodemask_t *nodemask,
unsigned long *totalpages)
{
struct zone *zone;
struct zoneref *z;
enum zone_type high_zoneidx = gfp_zone(gfp_mask);
bool cpuset_limited = false;
int nid;
/* Default to all available memory */
*totalpages = totalram_pages + total_swap_pages;
if (!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 (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 (nodemask && !nodes_subset(node_states[N_HIGH_MEMORY], *nodemask)) {
*totalpages = total_swap_pages;
for_each_node_mask(nid, *nodemask)
*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, zonelist,
high_zoneidx, nodemask)
if (!cpuset_zone_allowed_softwall(zone, gfp_mask))
cpuset_limited = true;
if (cpuset_limited) {
*totalpages = total_swap_pages;
for_each_node_mask(nid, cpuset_current_mems_allowed)
*totalpages += node_spanned_pages(nid);
return CONSTRAINT_CPUSET;
}
return CONSTRAINT_NONE;
}
#else
static enum oom_constraint constrained_alloc(struct zonelist *zonelist,
gfp_t gfp_mask, nodemask_t *nodemask,
unsigned long *totalpages)
{
*totalpages = totalram_pages + total_swap_pages;
return CONSTRAINT_NONE;
}
#endif
/*
* Simple selection loop. We chose the process with the highest
* number of 'points'. We expect the caller will lock the tasklist.
*
* (not docbooked, we don't want this one cluttering up the manual)
*/
static struct task_struct *select_bad_process(unsigned int *ppoints,
unsigned long totalpages, struct mem_cgroup *mem,
const nodemask_t *nodemask)
{
struct task_struct *g, *p;
struct task_struct *chosen = NULL;
*ppoints = 0;
do_each_thread(g, p) {
unsigned int points;
if (p->exit_state)
continue;
if (oom_unkillable_task(p, mem, nodemask))
continue;
/*
* This task already has access to memory reserves and is
* being killed. Don't allow any other task access to the
* memory reserve.
*
* Note: this may have a chance of deadlock if it gets
* blocked waiting for another task which itself is waiting
* for memory. Is there a better alternative?
*/
if (test_tsk_thread_flag(p, TIF_MEMDIE))
return ERR_PTR(-1UL);
if (!p->mm)
continue;
if (p->flags & PF_EXITING) {
/*
* If p is the current task and is in the process of
* releasing memory, we allow the "kill" to set
* TIF_MEMDIE, which will allow it to gain access to
* memory reserves. Otherwise, it may stall forever.
*
* The loop isn't broken here, however, in case other
* threads are found to have already been oom killed.
*/
if (p == current) {
chosen = p;
*ppoints = 1000;
} else {
/*
* If this task is not being ptraced on exit,
* then wait for it to finish before killing
* some other task unnecessarily.
*/
if (!(task_ptrace(p->group_leader) &
PT_TRACE_EXIT))
return ERR_PTR(-1UL);
}
}
points = oom_badness(p, mem, nodemask, totalpages);
if (points > *ppoints) {
chosen = p;
*ppoints = points;
}
} while_each_thread(g, p);
return chosen;
}
/**
* dump_tasks - dump current memory state of all system tasks
* @mem: 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, cpu, oom_adj
* value, oom_score_adj value, and name.
*
* Call with tasklist_lock read-locked.
*/
static void dump_tasks(const struct mem_cgroup *mem, const nodemask_t *nodemask)
{
struct task_struct *p;
struct task_struct *task;
pr_info("[ pid ] uid tgid total_vm rss cpu oom_adj oom_score_adj name\n");
for_each_process(p) {
if (oom_unkillable_task(p, mem, 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("[%5d] %5d %5d %8lu %8lu %3u %3d %5d %s\n",
task->pid, task_uid(task), task->tgid,
task->mm->total_vm, get_mm_rss(task->mm),
task_cpu(task), task->signal->oom_adj,
task->signal->oom_score_adj, task->comm);
task_unlock(task);
}
}
static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
struct mem_cgroup *mem, const nodemask_t *nodemask)
{
task_lock(current);
pr_warning("%s invoked oom-killer: gfp_mask=0x%x, order=%d, "
"oom_adj=%d, oom_score_adj=%d\n",
current->comm, gfp_mask, order, current->signal->oom_adj,
current->signal->oom_score_adj);
cpuset_print_task_mems_allowed(current);
task_unlock(current);
dump_stack();
mem_cgroup_print_oom_info(mem, p);
show_mem(SHOW_MEM_FILTER_NODES);
if (sysctl_oom_dump_tasks)
dump_tasks(mem, nodemask);
}
#define K(x) ((x) << (PAGE_SHIFT-10))
static int oom_kill_task(struct task_struct *p, struct mem_cgroup *mem)
{
struct task_struct *q;
struct mm_struct *mm;
p = find_lock_task_mm(p);
if (!p)
return 1;
/* mm cannot be safely dereferenced after task_unlock(p) */
mm = p->mm;
pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB\n",
task_pid_nr(p), p->comm, K(p->mm->total_vm),
K(get_mm_counter(p->mm, MM_ANONPAGES)),
K(get_mm_counter(p->mm, MM_FILEPAGES)));
task_unlock(p);
/*
* Kill all processes sharing p->mm in other thread groups, if any.
* They don't get access to memory reserves or a higher scheduler
* priority, though, to avoid depletion of all memory or task
* starvation. This prevents mm->mmap_sem livelock when an oom killed
* task 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.
*/
for_each_process(q)
if (q->mm == mm && !same_thread_group(q, p)) {
task_lock(q); /* Protect ->comm from prctl() */
pr_err("Kill process %d (%s) sharing same memory\n",
task_pid_nr(q), q->comm);
task_unlock(q);
force_sig(SIGKILL, q);
}
set_tsk_thread_flag(p, TIF_MEMDIE);
force_sig(SIGKILL, p);
return 0;
}
#undef K
static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
unsigned int points, unsigned long totalpages,
struct mem_cgroup *mem, nodemask_t *nodemask,
const char *message)
{
struct task_struct *victim = p;
struct task_struct *child;
struct task_struct *t = p;
unsigned int victim_points = 0;
if (printk_ratelimit())
dump_header(p, gfp_mask, order, mem, nodemask);
/*
* If the task is already exiting, don't alarm the sysadmin or kill
* its children or threads, just set TIF_MEMDIE so it can die quickly
*/
if (p->flags & PF_EXITING) {
set_tsk_thread_flag(p, TIF_MEMDIE);
return 0;
}
task_lock(p);
pr_err("%s: Kill process %d (%s) score %d or sacrifice child\n",
message, task_pid_nr(p), p->comm, points);
task_unlock(p);
/*
* If any of p's children has a different mm and is eligible for kill,
* the one with the highest badness() score is sacrificed for its
* parent. This attempts to lose the minimal amount of work done while
* still freeing memory.
*/
do {
list_for_each_entry(child, &t->children, sibling) {
unsigned int child_points;
if (child->mm == p->mm)
continue;
/*
* oom_badness() returns 0 if the thread is unkillable
*/
child_points = oom_badness(child, mem, nodemask,
totalpages);
if (child_points > victim_points) {
victim = child;
victim_points = child_points;
}
}
} while_each_thread(p, t);
return oom_kill_task(victim, mem);
}
/*
* Determines whether the kernel must panic because of the panic_on_oom sysctl.
*/
static void check_panic_on_oom(enum oom_constraint constraint, gfp_t gfp_mask,
int order, const nodemask_t *nodemask)
{
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;
}
read_lock(&tasklist_lock);
dump_header(NULL, gfp_mask, order, NULL, nodemask);
read_unlock(&tasklist_lock);
panic("Out of memory: %s panic_on_oom is enabled\n",
sysctl_panic_on_oom == 2 ? "compulsory" : "system-wide");
}
#ifdef CONFIG_CGROUP_MEM_RES_CTLR
void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
{
unsigned long limit;
unsigned int points = 0;
struct task_struct *p;
/*
* If current has a pending SIGKILL, then automatically select it. The
* goal is to allow it to allocate so that it may quickly exit and free
* its memory.
*/
if (fatal_signal_pending(current)) {
set_thread_flag(TIF_MEMDIE);
return;
}
check_panic_on_oom(CONSTRAINT_MEMCG, gfp_mask, 0, NULL);
limit = mem_cgroup_get_limit(mem) >> PAGE_SHIFT;
read_lock(&tasklist_lock);
retry:
p = select_bad_process(&points, limit, mem, NULL);
if (!p || PTR_ERR(p) == -1UL)
goto out;
if (oom_kill_process(p, gfp_mask, 0, points, limit, mem, NULL,
"Memory cgroup out of memory"))
goto retry;
out:
read_unlock(&tasklist_lock);
}
#endif
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);
/*
* Try to acquire the OOM killer lock for the zones in zonelist. Returns zero
* if a parallel OOM killing is already taking place that includes a zone in
* the zonelist. Otherwise, locks all zones in the zonelist and returns 1.
*/
int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
{
struct zoneref *z;
struct zone *zone;
int ret = 1;
spin_lock(&zone_scan_lock);
for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
if (zone_is_oom_locked(zone)) {
ret = 0;
goto out;
}
}
for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
/*
* Lock each zone in the zonelist under zone_scan_lock so a
* parallel invocation of try_set_zonelist_oom() doesn't succeed
* when it shouldn't.
*/
zone_set_flag(zone, ZONE_OOM_LOCKED);
}
out:
spin_unlock(&zone_scan_lock);
return ret;
}
/*
* Clears the ZONE_OOM_LOCKED flag for all zones in the zonelist so that failed
* allocation attempts with zonelists containing them may now recall the OOM
* killer, if necessary.
*/
void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
{
struct zoneref *z;
struct zone *zone;
spin_lock(&zone_scan_lock);
for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
zone_clear_flag(zone, ZONE_OOM_LOCKED);
}
spin_unlock(&zone_scan_lock);
}
/*
* Try to acquire the oom killer lock for all system zones. Returns zero if a
* parallel oom killing is taking place, otherwise locks all zones and returns
* non-zero.
*/
static int try_set_system_oom(void)
{
struct zone *zone;
int ret = 1;
spin_lock(&zone_scan_lock);
for_each_populated_zone(zone)
if (zone_is_oom_locked(zone)) {
ret = 0;
goto out;
}
for_each_populated_zone(zone)
zone_set_flag(zone, ZONE_OOM_LOCKED);
out:
spin_unlock(&zone_scan_lock);
return ret;
}
/*
* Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
* attempts or page faults may now recall the oom killer, if necessary.
*/
static void clear_system_oom(void)
{
struct zone *zone;
spin_lock(&zone_scan_lock);
for_each_populated_zone(zone)
zone_clear_flag(zone, ZONE_OOM_LOCKED);
spin_unlock(&zone_scan_lock);
}
/**
* out_of_memory - kill the "best" process when we run out of memory
* @zonelist: zonelist pointer
* @gfp_mask: memory allocation flags
* @order: amount of memory being requested as a power of 2
* @nodemask: nodemask passed to page allocator
*
* 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.
*/
void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
int order, nodemask_t *nodemask)
{
const nodemask_t *mpol_mask;
struct task_struct *p;
unsigned long totalpages;
unsigned long freed = 0;
unsigned int points;
enum oom_constraint constraint = CONSTRAINT_NONE;
int killed = 0;
blocking_notifier_call_chain(&oom_notify_list, 0, &freed);
if (freed > 0)
/* Got some memory back in the last second. */
return;
/*
* If current has a pending SIGKILL, then automatically select it. The
* goal is to allow it to allocate so that it may quickly exit and free
* its memory.
*/
if (fatal_signal_pending(current)) {
set_thread_flag(TIF_MEMDIE);
return;
}
/*
* Check if there were limitations on the allocation (only relevant for
* NUMA) that may require different handling.
*/
constraint = constrained_alloc(zonelist, gfp_mask, nodemask,
&totalpages);
mpol_mask = (constraint == CONSTRAINT_MEMORY_POLICY) ? nodemask : NULL;
check_panic_on_oom(constraint, gfp_mask, order, mpol_mask);
read_lock(&tasklist_lock);
if (sysctl_oom_kill_allocating_task &&
!oom_unkillable_task(current, NULL, nodemask) &&
current->mm && !atomic_read(&current->mm->oom_disable_count)) {
/*
* oom_kill_process() needs tasklist_lock held. If it returns
* non-zero, current could not be killed so we must fallback to
* the tasklist scan.
*/
if (!oom_kill_process(current, gfp_mask, order, 0, totalpages,
NULL, nodemask,
"Out of memory (oom_kill_allocating_task)"))
goto out;
}
retry:
p = select_bad_process(&points, totalpages, NULL, mpol_mask);
if (PTR_ERR(p) == -1UL)
goto out;
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!p) {
dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
read_unlock(&tasklist_lock);
panic("Out of memory and no killable processes...\n");
}
if (oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
nodemask, "Out of memory"))
goto retry;
killed = 1;
out:
read_unlock(&tasklist_lock);
/*
* Give "p" a good chance of killing itself before we
* retry to allocate memory unless "p" is current
*/
if (killed && !test_thread_flag(TIF_MEMDIE))
schedule_timeout_uninterruptible(1);
}
/*
* The pagefault handler calls here because it is out of memory, so kill a
* memory-hogging task. If a populated zone has ZONE_OOM_LOCKED set, a parallel
* oom killing is already in progress so do nothing. If a task is found with
* TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
*/
void pagefault_out_of_memory(void)
{
if (try_set_system_oom()) {
out_of_memory(NULL, 0, 0, NULL);
clear_system_oom();
}
if (!test_thread_flag(TIF_MEMDIE))
schedule_timeout_uninterruptible(1);
}
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