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mm, oom: get rid of signal_struct::oom_victims 

After "oom: keep mm of the killed task available" we can safely detect
an oom victim by checking task->signal->oom_mm so we do not need the
signal_struct counter anymore so let's get rid of it.

This alone wouldn't be sufficient for nommu archs because
exit_oom_victim doesn't hide the process from the oom killer anymore.
We can, however, mark the mm with a MMF flag in __mmput.  We can reuse
MMF_OOM_REAPED and rename it to a more generic MMF_OOM_SKIP.

Link: http://lkml.kernel.org/r/1472119394-11342-6-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Michal Hocko 2016-10-07 16:58:57 -07:00 committed by Linus Torvalds
parent 7283094ec3
commit 862e3073b3
4 changed files with 14 additions and 12 deletions
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5
include/linux/oom.h
View File

@ -58,6 +58,11 @@ static inline bool oom_task_origin(const struct task_struct *p)
return p->signal->oom_flag_origin;
}
static inline bool tsk_is_oom_victim(struct task_struct * tsk)
{
return tsk->signal->oom_mm;
}
extern unsigned long oom_badness(struct task_struct *p,
struct mem_cgroup *memcg, const nodemask_t *nodemask,
unsigned long totalpages);

3
include/linux/sched.h
View File

@ -524,7 +524,7 @@ static inline int get_dumpable(struct mm_struct *mm)
#define MMF_HAS_UPROBES 19 /* has uprobes */
#define MMF_RECALC_UPROBES 20 /* MMF_HAS_UPROBES can be wrong */
#define MMF_OOM_REAPED 21 /* mm has been already reaped */
#define MMF_OOM_SKIP 21 /* mm is of no interest for the OOM killer */
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK)
@ -672,7 +672,6 @@ struct signal_struct {
atomic_t sigcnt;
atomic_t live;
int nr_threads;
atomic_t oom_victims; /* # of TIF_MEDIE threads in this thread group */
struct list_head thread_head;
wait_queue_head_t wait_chldexit; /* for wait4() */

1
kernel/fork.c
View File

@ -862,6 +862,7 @@ static inline void __mmput(struct mm_struct *mm)
}
if (mm->binfmt)
module_put(mm->binfmt->module);
set_bit(MMF_OOM_SKIP, &mm->flags);
mmdrop(mm);
}

17
mm/oom_kill.c
View File

@ -186,7 +186,7 @@ unsigned long oom_badness(struct task_struct *p, struct mem_cgroup *memcg,
*/
adj = (long)p->signal->oom_score_adj;
if (adj == OOM_SCORE_ADJ_MIN ||
test_bit(MMF_OOM_REAPED, &p->mm->flags) ||
test_bit(MMF_OOM_SKIP, &p->mm->flags) ||
in_vfork(p)) {
task_unlock(p);
return 0;
@ -296,11 +296,11 @@ static int oom_evaluate_task(struct task_struct *task, void *arg)
/*
* 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_REAPED because chances that it would release
* the task has MMF_OOM_SKIP because chances that it would release
* any memory is quite low.
*/
if (!is_sysrq_oom(oc) && atomic_read(&task->signal->oom_victims)) {
if (test_bit(MMF_OOM_REAPED, &task->signal->oom_mm->flags))
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;
}
@ -572,7 +572,7 @@ done:
* 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_REAPED, &mm->flags);
set_bit(MMF_OOM_SKIP, &mm->flags);
/* Drop a reference taken by wake_oom_reaper */
put_task_struct(tsk);
@ -654,8 +654,6 @@ static void mark_oom_victim(struct task_struct *tsk)
if (test_and_set_tsk_thread_flag(tsk, TIF_MEMDIE))
return;
atomic_inc(&tsk->signal->oom_victims);
/* oom_mm is bound to the signal struct life time. */
if (!cmpxchg(&tsk->signal->oom_mm, NULL, mm))
atomic_inc(&tsk->signal->oom_mm->mm_count);
@ -677,7 +675,6 @@ void exit_oom_victim(struct task_struct *tsk)
{
if (!test_and_clear_tsk_thread_flag(tsk, TIF_MEMDIE))
return;
atomic_dec(&tsk->signal->oom_victims);
if (!atomic_dec_return(&oom_victims))
wake_up_all(&oom_victims_wait);
@ -769,7 +766,7 @@ static bool task_will_free_mem(struct task_struct *task)
* 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_REAPED, &mm->flags))
if (test_bit(MMF_OOM_SKIP, &mm->flags))
return false;
if (atomic_read(&mm->mm_users) <= 1)
@ -906,7 +903,7 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
* killer to guarantee OOM forward progress.
*/
can_oom_reap = false;
set_bit(MMF_OOM_REAPED, &mm->flags);
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);