>From 0b36864d4100ecbdcaa2fc2d1927c9e270f1b629 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Date: Wed, 17 Feb 2016 16:37:59 +0900
Subject: [PATCH 6/6] mm,oom: wait for OOM victims when using oom_kill_allocating_task == 1
Currently, out_of_memory() does not wait for existing TIF_MEMDIE threads
if /proc/sys/vm/oom_kill_allocating_task is set to 1. This can result in
killing more OOM victims than needed. We can wait for the OOM reaper to
reap memory used by existing TIF_MEMDIE threads if possible. If the OOM
reaper is not available, the system will be kept OOM stalled until an
OOM-unkillable thread does a GFP_FS allocation request and calls
oom_kill_allocating_task == 0 path.
This patch changes oom_kill_allocating_task == 1 case to call
select_bad_process() in order to wait for existing TIF_MEMDIE threads.
Since "mm,oom: exclude TIF_MEMDIE processes from candidates.",
"mm,oom: don't abort on exiting processes when selecting a victim.",
"mm,oom: exclude oom_task_origin processes if they are OOM victims.",
"mm,oom: exclude oom_task_origin processes if they are OOM-unkillable."
and "mm,oom: Re-enable OOM killer using timers." made sure that we never
wait for TIF_MEMDIE threads forever, waiting for TIF_MEMDIE threads for
oom_kill_allocating_task == 1 does not cause OOM livelock problem.
After this patch, we can safely merge the OOM reaper in the simplest
form, without worrying about corner cases.
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 23 ++++++++++++-----------
1 file changed, 12 insertions(+), 11 deletions(-)
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index fba2c62..9cd1cd1 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -737,15 +737,6 @@ bool out_of_memory(struct oom_control *oc)
oc->nodemask = NULL;
check_panic_on_oom(oc, constraint, NULL);
- if (sysctl_oom_kill_allocating_task && current->mm &&
- !oom_unkillable_task(current, NULL, oc->nodemask) &&
- current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
- get_task_struct(current);
- oom_kill_process(oc, current, 0, totalpages, NULL,
- "Out of memory (oom_kill_allocating_task)");
- return true;
- }
-
p = select_bad_process(oc, &points, totalpages);
/* Found nothing?!?! Either we hang forever, or we panic. */
if (!p && !is_sysrq_oom(oc)) {
@@ -753,8 +744,18 @@ bool out_of_memory(struct oom_control *oc)
panic("Out of memory and no killable processes...\n");
}
if (p && p != (void *)-1UL) {
- oom_kill_process(oc, p, points, totalpages, NULL,
- "Out of memory");
+ const char *message = "Out of memory";
+
+ if (sysctl_oom_kill_allocating_task && current->mm &&
+ !oom_unkillable_task(current, NULL, oc->nodemask) &&
+ current->signal->oom_score_adj != OOM_SCORE_ADJ_MIN) {
+ put_task_struct(p);
+ p = current;
+ get_task_struct(p);
+ message = "Out of memory (oom_kill_allocating_task)";
+ points = 0;
+ }
+ oom_kill_process(oc, p, points, totalpages, NULL, message);
/*
* Give the killed process a good chance to exit before trying
* to allocate memory again.
--
1.8.3.1
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