tree e1c654ed7e27649b7d0152d8ad02115175b92554
parent 95df2d8860b2fd0759722fe691c244f0769829c6
author Oleg Nesterov <oleg@redhat.com> 1312036502 +0200
committer Greg Kroah-Hartman <gregkh@suse.de> 1312400571 -0700

oom: task->mm == NULL doesn't mean the memory was freed

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 <oleg@redhat.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>