linux-kernel - [PATCH] kthread_worker: Initialize dynamically allocated spinlock properly for lockdep

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Date:	Sun, 19 Dec 2010 07:49:35 -0500
From:	Andy Walls <awalls@...metrocast.net>
To:	linux-kernel@...r.kernel.org
Cc:	nicolas.mailhot@...oste.net, Tejun Heo <tj@...nel.org>,
	Jarod Wilson <jarod@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Hans Verkuil <hverkuil@...all.nl>
Subject: [PATCH] kthread_worker: Initialize dynamically allocated spinlock
 properly for lockdep

init_kthread_worker(), via KTHREAD_WORKER_INIT(), used an
initializer for static spin_lock objects, SPIN_LOCK_UNLOCKED, on
a dynamically allocated kthread_worker object's internal spinlock_t.
This causes lockdep to gripe:

	INFO: trying to register non-static key.
	the code is fine but needs lockdep annotation.
	turning off the locking correctness validator.

To keep lockdep happy, use spin_lock_init() for dynamically
allocated kthread_worker objects' internal spinlock_t.

Reported-by: Nicolas <nicolas.mailhot@...oste.net>
Signed-off-by: Andy Walls <awalls@...metrocast.net>

Cc: Tejun Heo <tj@...nel.org>
Cc: Jarod Wilson <jarod@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Mauro Carvalho Chehab <mchehab@...hat.com>
Cc: Hans Verkuil <hverkuil@...all.nl>

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index 685ea65..e65d0b1 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -83,7 +83,13 @@ struct kthread_work {
 
 static inline void init_kthread_worker(struct kthread_worker *worker)
 {
-	*worker = (struct kthread_worker)KTHREAD_WORKER_INIT(*worker);
+	/*
+	 * Lockdep complains if a dynamically allocated worker's spinlock_t
+	 * is initialzed using SPIN_LOCK_UNLOCKED.
+	 */
+	spin_lock_init(&worker->lock);
+	INIT_LIST_HEAD(&worker->work_list);
+	worker->task = NULL;
 }
 
 static inline void init_kthread_work(struct kthread_work *work,


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