[PATCH] mm/oom_kill.c: don't kill TASK_UNINTERRUPTIBLE tasks

[Kyle Walker]

Currently, the oom killer will attempt to kill a process that is in
TASK_UNINTERRUPTIBLE state. For tasks in this state for an exceptional
period of time, such as processes writing to a frozen filesystem during
a lengthy backup operation, this can result in a deadlock condition as
related processes memory access will stall within the page fault
handler.

Within oom_unkillable_task(), check for processes in
TASK_UNINTERRUPTIBLE (TASK_KILLABLE omitted). The oom killer will
move on to another task.

Signed-off-by: Kyle Walker <kwalker@xxxxxxxxxx>
---
 mm/oom_kill.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 1ecc0bc..66f03f8 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -131,6 +131,10 @@ static bool oom_unkillable_task(struct task_struct *p,
 	if (memcg && !task_in_mem_cgroup(p, memcg))
 		return true;
 
+	/* Uninterruptible tasks should not be killed unless in TASK_WAKEKILL */
+	if (p->state == TASK_UNINTERRUPTIBLE)
+		return true;
+
 	/* p may not have freeable memory in nodemask */
 	if (!has_intersects_mems_allowed(p, nodemask))
 		return true;
-- 
2.4.3

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