We can revert commit e2fe14564d3316d1 ("oom_reaper: close race with
exiting task") because oom_has_pending_mm() which will return true until
exit_oom_mm() is called after OOM victim's mm is reclaimed by __mmput()
or oom_reap_task() can close that race.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 29 ++++-------------------------
1 file changed, 4 insertions(+), 25 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index fab0bec..232c1ce 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -476,28 +476,9 @@ static bool __oom_reap_task(struct task_struct *tsk, struct mm_struct *mm)
struct vm_area_struct *vma;
struct zap_details details = {.check_swap_entries = true,
.ignore_dirty = true};
- bool ret = true;
- /*
- * We have to make sure to not race with the victim exit path
- * and cause premature new oom victim selection:
- * __oom_reap_task exit_mm
- * mmget_not_zero
- * mmput
- * atomic_dec_and_test
- * exit_oom_victim
- * [...]
- * out_of_memory
- * select_bad_process
- * # no TIF_MEMDIE task selects new victim
- * unmap_page_range # frees some memory
- */
- mutex_lock(&oom_lock);
-
- if (!down_read_trylock(&mm->mmap_sem)) {
- ret = false;
- goto unlock_oom;
- }
+ if (!down_read_trylock(&mm->mmap_sem))
+ return false;
/*
* increase mm_users only after we know we will reap something so
@@ -506,7 +487,7 @@ static bool __oom_reap_task(struct task_struct *tsk, struct mm_struct *mm)
*/
if (!mmget_not_zero(mm)) {
up_read(&mm->mmap_sem);
- goto unlock_oom;
+ return true;
}
tlb_gather_mmu(&tlb, mm, 0, -1);
@@ -554,9 +535,7 @@ static bool __oom_reap_task(struct task_struct *tsk, struct mm_struct *mm)
* put the oom_reaper out of the way.
*/
mmput_async(mm);
-unlock_oom:
- mutex_unlock(&oom_lock);
- return ret;
+ return true;
}
#define MAX_OOM_REAP_RETRIES 10
--
1.8.3.1
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