Commit 63a8ca9b authored Feb 11, 2015 by Michal Hocko Committed by Linus Torvalds Feb 11, 2015

oom: thaw the OOM victim if it is frozen



oom_kill_process only sets TIF_MEMDIE flag and sends a signal to the
victim.  This is basically noop when the task is frozen though because the
task sleeps in the uninterruptible sleep.  The victim is eventually thawed
later when oom_scan_process_thread meets the task again in a later OOM
invocation so the OOM killer doesn't live lock.  But this is less than
optimal.

Let's add __thaw_task into mark_tsk_oom_victim after we set TIF_MEMDIE to
the victim.  We are not checking whether the task is frozen because that
would be racy and __thaw_task does that already.  oom_scan_process_thread
doesn't need to care about freezer anymore as TIF_MEMDIE and freezer are
excluded completely now.

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 49550b60

mm/oom_kill.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -266,8 +266,6 @@ enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
		* Don't allow any other task to have access to the reserves.
		*/
		if (test_tsk_thread_flag(task, TIF_MEMDIE)) {
		if (unlikely(frozen(task)))
		__thaw_task(task);
		if (!force_kill)
		return OOM_SCAN_ABORT;
		}
		@@ -423,6 +421,14 @@ void note_oom_kill(void)
		void mark_tsk_oom_victim(struct task_struct *tsk)
		{
		set_tsk_thread_flag(tsk, TIF_MEMDIE);

		/*
		* Make sure that the task is woken up from uninterruptible sleep
		* if it is frozen because OOM killer wouldn't be able to free
		* any memory and livelock. freezing_slow_path will tell the freezer
		* that TIF_MEMDIE tasks should be ignored.
		*/
		__thaw_task(tsk);
		}

		/**

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