Messages in this thread Patch in this message | | | Subject | Re: [RFC PATCH -v2] mm, oom: introduce oom reaper | From | Tetsuo Handa <> | Date | Sun, 29 Nov 2015 01:10:10 +0900 |
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Tetsuo Handa wrote: > > Users of mmap_sem which need it for write should be carefully reviewed > > to use _killable waiting as much as possible and reduce allocations > > requests done with the lock held to absolute minimum to reduce the risk > > even further. > > It will be nice if we can have down_write_killable()/down_read_killable().
It will be nice if we can also have __GFP_KILLABLE. Although currently it can't be perfect because reclaim functions called from __alloc_pages_slowpath() use unkillable waits, starting from just bail out as with __GFP_NORETRY when fatal_signal_pending(current) is true will be helpful.
So far I'm hitting no problem with testers except the one using mmap()/munmap().
I think that cmpxchg() was not needed.
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index c2ab7f9..1a65739 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -483,8 +483,6 @@ static int oom_reaper(void *unused) static void wake_oom_reaper(struct mm_struct *mm) { - struct mm_struct *old_mm; - if (!oom_reaper_th) return; @@ -492,14 +490,15 @@ static void wake_oom_reaper(struct mm_struct *mm) * Make sure that only a single mm is ever queued for the reaper * because multiple are not necessary and the operation might be * disruptive so better reduce it to the bare minimum. + * Caller is serialized by oom_lock mutex. */ - old_mm = cmpxchg(&mm_to_reap, NULL, mm); - if (!old_mm) { + if (!mm_to_reap) { /* * Pin the given mm. Use mm_count instead of mm_users because * we do not want to delay the address space tear down. */ atomic_inc(&mm->mm_count); + mm_to_reap = mm; wake_up(&oom_reaper_wait); } }
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