oom: task->mm == NULL doesn't mean the memory was freed
authorOleg Nesterov <oleg@redhat.com>
Sat, 30 Jul 2011 14:35:02 +0000 (16:35 +0200)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 2 Aug 2011 01:24:12 +0000 (15:24 -1000)
commitc027a474a68065391c8773f6e83ed5412657e369
tree6d3c8caba5ebf736c3f9ef3cacb708cbdb9869c2
parentcfe22345ad5ef29e192e157fdc3e17d357e4bc24
oom: task->mm == NULL doesn't mean the memory was freed

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 <oleg@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/oom_kill.c