"mm, oom_reaper: do not attempt to reap a task twice" tried to give the
OOM reaper one more chance to retry using MMF_OOM_NOT_REAPABLE flag. But
the usefulness of the flag is rather limited and actually never shown
in practice. If the flag is set, it means that the holder of mm->mmap_sem
cannot call up_write() due to presumably being blocked at unkillable wait
waiting for other thread's memory allocation. But since one of threads
sharing that mm will queue that mm immediately via task_will_free_mem()
shortcut (otherwise, oom_badness() will select the same mm again due to
oom_score_adj value unchanged), retrying MMF_OOM_NOT_REAPABLE mm is
unlikely helpful.
Let's always set MMF_OOM_REAPED.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
include/linux/sched.h | 1 -
mm/oom_kill.c | 15 +++------------
2 files changed, 3 insertions(+), 13 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 553af29..c0efd80 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -523,7 +523,6 @@ 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 951eb1b..9f0022e 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -567,20 +567,11 @@ static void oom_reap_task(struct task_struct *tsk)
if (attempts <= MAX_OOM_REAP_RETRIES)
goto done;
+ /* Ignore this mm because somebody can't call up_write(mmap_sem). */
+ set_bit(MMF_OOM_REAPED, &mm->flags);
+
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.
- */
- if (test_and_set_bit(MMF_OOM_NOT_REAPABLE, &mm->flags)) {
- pr_info("oom_reaper: giving up pid:%d (%s)\n",
- task_pid_nr(tsk), tsk->comm);
- set_bit(MMF_OOM_REAPED, &mm->flags);
- }
debug_show_all_locks();
done:
--
1.8.3.1
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