[v3.13][v3.14][Regression] kthread: make kthread_create() killable

[Tetsuo Handa]

Hello.

Although the process who is sending SIGKILL to systemd-udevd is not
identified yet, adding wait_for_completion_timeout() can solve this
regression. Therefore, I'd like to propose this patch for 3.14-final
and 3.13-stable.

Regards.
----------
>From c6562e5d774dd1f36724197dbcb8976cccfaab53 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
Date: Sun, 16 Mar 2014 22:44:23 +0900
Subject: [PATCH] kthread: Do not leave kthread_create() immediately upon SIGKILL.

Commit 786235ee "kthread: make kthread_create() killable" changed to
leave kthread_create() as soon as receiving SIGKILL. But this change
caused boot failures if systemd-udevd received SIGKILL (probably due
to timeout) while loading SCSI controller drivers using
finit_module() [1].

Therefore, this patch changes kthread_create() to wait for 10 more
seconds after receiving SIGKILL, unless chosen by the OOM killer,
in order to give the kthreadd a chance to complete the request.

  [1] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1276705

Signed-off-by: Tetsuo Handa <penguin-kernel at I-love.SAKURA.ne.jp>
Cc: <stable at vger.kernel.org> [3.13+]
---
 kernel/kthread.c |   12 ++++++++++++
 1 files changed, 12 insertions(+), 0 deletions(-)

diff --git a/kernel/kthread.c b/kernel/kthread.c
index b5ae3ee..52ae7dc 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -292,6 +292,17 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
 	 * new kernel thread.
 	 */
 	if (unlikely(wait_for_completion_killable(&done))) {
+		int i = 0;
+
+		/*
+		 * I got SIGKILL, but wait for 10 more seconds for completion
+		 * unless chosen by the OOM killer. This delay is there as a
+		 * workaround for boot failure caused by SIGKILL upon device
+		 * driver initialization timeout.
+		 */
+		while (i++ < 10 && !test_tsk_thread_flag(current, TIF_MEMDIE))
+			if (wait_for_completion_timeout(&done, HZ))
+				goto ready;
 		/*
 		 * If I was SIGKILLed before kthreadd (or new kernel thread)
 		 * calls complete(), leave the cleanup of this structure to
@@ -305,6 +316,7 @@ struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
 		 */
 		wait_for_completion(&done);
 	}
+ready:
 	task = create->result;
 	if (!IS_ERR(task)) {
 		static const struct sched_param param = { .sched_priority = 0 };
-- 
1.7.1