From 862e3073b3eed13f17bd6be6ca6052db15c0b728 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Fri, 7 Oct 2016 16:58:57 -0700 Subject: [PATCH] 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 Cc: Tetsuo Handa Cc: Oleg Nesterov Cc: David Rientjes Cc: Vladimir Davydov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/oom.h | 5 +++++ include/linux/sched.h | 3 +-- kernel/fork.c | 1 + mm/oom_kill.c | 17 +++++++---------- 4 files changed, 14 insertions(+), 12 deletions(-) diff --git a/include/linux/oom.h b/include/linux/oom.h index 17946e5121b6..b61357d07170 100644 --- a/include/linux/oom.h +++ b/include/linux/oom.h @@ -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); diff --git a/include/linux/sched.h b/include/linux/sched.h index c4b588358296..af0721364788 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -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() */ diff --git a/kernel/fork.c b/kernel/fork.c index 5650e35dda43..9a8ec66cd4df 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -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); } diff --git a/mm/oom_kill.c b/mm/oom_kill.c index f16ec0840a0e..e2a2c35dd493 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -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); -- 2.20.1