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Commit e1099a69 authored by David Rientjes's avatar David Rientjes Committed by Greg Kroah-Hartman
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android, lmk: avoid setting TIF_MEMDIE if process has already exited 



TIF_MEMDIE should not be set on a process if it does not have a valid
->mm, and this is protected by task_lock().

If TIF_MEMDIE gets set after the mm has detached, and the process fails to
exit, then the oom killer will defer forever waiting for it to exit.

Make sure that the mm is still valid before setting TIF_MEMDIE by way of
mark_tsk_oom_victim().

Cc: "Arve Hjønnevåg" <arve@android.com>
Cc: Riley Andrews <riandrews@android.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 56f40e52

drivers/staging/android/lowmemorykiller.c

+12 −5
Original line number Diff line number Diff line
@@ -156,20 +156,27 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc) 
			     p->pid, p->comm, oom_score_adj, tasksize);

	}

	if (selected) {

		lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",

			     selected->pid, selected->comm,

			     selected_oom_score_adj, selected_tasksize);

		lowmem_deathpending_timeout = jiffies + HZ;

		task_lock(selected);

		if (!selected->mm) {

			/* Already exited, cannot do mark_tsk_oom_victim() */

			task_unlock(selected);

			goto out;

		}

		/*

		 * FIXME: lowmemorykiller shouldn't abuse global OOM killer

		 * infrastructure. There is no real reason why the selected

		 * task should have access to the memory reserves.

		 */

		mark_tsk_oom_victim(selected);

		task_unlock(selected);

		lowmem_print(1, "send sigkill to %d (%s), adj %hd, size %d\n",

			     selected->pid, selected->comm,

			     selected_oom_score_adj, selected_tasksize);

		lowmem_deathpending_timeout = jiffies + HZ;

		send_sig(SIGKILL, selected, 0);

		rem += selected_tasksize;

	}



out:

	lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",

		     sc->nr_to_scan, sc->gfp_mask, rem);

	rcu_read_unlock();