Commit c027a474 authored Jul 30, 2011 by Oleg Nesterov Committed by Linus Torvalds Aug 01, 2011

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>

parent cfe22345

mm/oom_kill.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -303,7 +303,7 @@ static struct task_struct select_bad_process(unsigned int ppoints,
		do_each_thread(g, p) {
		unsigned int points;

		if (!p->mm)
		if (p->exit_state)
		continue;
		if (oom_unkillable_task(p, mem, nodemask))
		continue;
		@@ -319,6 +319,8 @@ static struct task_struct select_bad_process(unsigned int ppoints,
		*/
		if (test_tsk_thread_flag(p, TIF_MEMDIE))
		return ERR_PTR(-1UL);
		if (!p->mm)
		continue;

		if (p->flags & PF_EXITING) {
		/*