This is a note to let you know that I've just added the patch titled
oom: task->mm == NULL doesn't mean the memory was freed
to the 2.6.39-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
oom-task-mm-null-doesn-t-mean-the-memory-was-freed.patch
and it can be found in the queue-2.6.39 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From c027a474a68065391c8773f6e83ed5412657e369 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <[email protected]>
Date: Sat, 30 Jul 2011 16:35:02 +0200
Subject: oom: task->mm == NULL doesn't mean the memory was freed
From: Oleg Nesterov <[email protected]>
commit c027a474a68065391c8773f6e83ed5412657e369 upstream.
exit_mm() sets ->mm == NULL then it does mmput()->exit_mmap() which
frees the memory.
However select_bad_process() checks ->mm != NULL before TIF_MEMDIE,
so it continues to kill other tasks even if we have the oom-killed
task freeing its memory.
Change select_bad_process() to check ->mm after TIF_MEMDIE, but skip
the tasks which have already passed exit_notify() to ensure a zombie
with TIF_MEMDIE set can't block oom-killer. Alternatively we could
probably clear TIF_MEMDIE after exit_mmap().
Signed-off-by: Oleg Nesterov <[email protected]>
Reviewed-by: KOSAKI Motohiro <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
mm/oom_kill.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -285,7 +285,7 @@ static struct task_struct *select_bad_pr
do_each_thread(g, p) {
unsigned int points;
- if (!p->mm)
+ if (p->exit_state)
continue;
if (oom_unkillable_task(p, mem, nodemask))
continue;
@@ -301,6 +301,8 @@ static struct task_struct *select_bad_pr
*/
if (test_tsk_thread_flag(p, TIF_MEMDIE))
return ERR_PTR(-1UL);
+ if (!p->mm)
+ continue;
if (p->flags & PF_EXITING) {
/*
Patches currently in stable-queue which might be from [email protected] are
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