From 11a410d516e89320fe0817606eeab58f36c22968 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 28 Jul 2016 15:44:58 -0700 Subject: [PATCH] mm, oom_reaper: do not attempt to reap a task more than twice oom_reaper relies on the mmap_sem for read to do its job. Many places which might block readers have been converted to use down_write_killable and that has reduced chances of the contention a lot. Some paths where the mmap_sem is held for write can take other locks and they might either be not prepared to fail due to fatal signal pending or too impractical to be changed. This patch introduces MMF_OOM_NOT_REAPABLE flag which gets set after the first attempt to reap a task's mm fails. If the flag is present after the failure then we set MMF_OOM_REAPED to hide this mm from the oom killer completely so it can go and chose another victim. As a result a risk of OOM deadlock when the oom victim would be blocked indefinetly and so the oom killer cannot make any progress should be mitigated considerably while we still try really hard to perform all reclaim attempts and stay predictable in the behavior. Link: http://lkml.kernel.org/r/1466426628-15074-10-git-send-email-mhocko@kernel.org Signed-off-by: Michal Hocko Acked-by: Oleg Nesterov Cc: Vladimir Davydov Cc: David Rientjes Cc: Tetsuo Handa Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/sched.h | 1 + mm/oom_kill.c | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index c0efd80ba40f..553af2923824 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -523,6 +523,7 @@ 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_NOT_REAPABLE 22 /* mm couldn't be reaped */ #define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK) diff --git a/mm/oom_kill.c b/mm/oom_kill.c index 36d5dd88d990..bfddc93ccd34 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -556,8 +556,27 @@ static void oom_reap_task(struct task_struct *tsk) schedule_timeout_idle(HZ/10); if (attempts > MAX_OOM_REAP_RETRIES) { + struct task_struct *p; + pr_info("oom_reaper: unable to reap pid:%d (%s)\n", task_pid_nr(tsk), tsk->comm); + + /* + * If we've already tried to reap this task in the past and + * failed it probably doesn't make much sense to try yet again + * so hide the mm from the oom killer so that it can move on + * to another task with a different mm struct. + */ + p = find_lock_task_mm(tsk); + if (p) { + if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &p->mm->flags)) { + pr_info("oom_reaper: giving up pid:%d (%s)\n", + task_pid_nr(tsk), tsk->comm); + set_bit(MMF_OOM_REAPED, &p->mm->flags); + } + task_unlock(p); + } + debug_show_all_locks(); } -- 2.30.2