[RFC PATCH 4/6] oom, oom_reaper: consider mmget_not_zero as a failure
From: Michal Hocko <mhocko@kernel.org>
Date: 2016-07-01 09:26:59
Subsystem:
memory management, memory management - oom killer, the rest · Maintainers:
Andrew Morton, Michal Hocko, Linus Torvalds
From: Michal Hocko <mhocko@suse.com> mmget_not_zero failing means that we are racing with mmput->__mmput and we are currently interpreting this as a success because we believe that __mmput will release the address space. This is not guaranteed though because at least exit_aio might wait on IO and it is not entirely clear whether it will terminate in a bounded amount of time. It is hard to tell what else is lurking there. This patch makes this path more conservative and we report a failure which will lead to setting MMF_OOM_NOT_REAPABLE and MMF_OOM_REAPED if this state is permanent. Signed-off-by: Michal Hocko <mhocko@suse.com> --- mm/oom_kill.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 4ac089cba353..b2210b6c38ba 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c@@ -460,7 +460,7 @@ static bool __oom_reap_task(struct task_struct *tsk) struct mm_struct *mm = NULL; struct zap_details details = {.check_swap_entries = true, .ignore_dirty = true}; - bool ret = true; + bool ret = false; /* * We have to make sure to not race with the victim exit path
@@ -479,10 +479,8 @@ static bool __oom_reap_task(struct task_struct *tsk) mutex_lock(&oom_lock); mm = tsk->signal->oom_mm; - if (!down_read_trylock(&mm->mmap_sem)) { - ret = false; + if (!down_read_trylock(&mm->mmap_sem)) goto unlock_oom; - } /* * increase mm_users only after we know we will reap something so
@@ -494,6 +492,7 @@ static bool __oom_reap_task(struct task_struct *tsk) goto unlock_oom; } + ret = true; tlb_gather_mmu(&tlb, mm, 0, -1); for (vma = mm->mmap ; vma; vma = vma->vm_next) { if (is_vm_hugetlb_page(vma))
--
2.8.1
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>