From: Oleg Nesterov <oleg@redhat.com>
Date: Sat, 30 Jul 2011 14:35:02 +0000 (+0200)
Subject: oom: task->mm == NULL doesn't mean the memory was freed
X-Git-Tag: v3.1-rc1~88
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c027a474a68065391c8773f6e83ed5412657e369;p=pandora-kernel.git

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>
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