kthread: Do not use TIMER_IRQSAFE

The TIMER_IRQSAFE usage was introduced in commit 22597dc3 ("kthread:
initial support for delayed kthread work") which modelled the delayed
kthread code after workqueue's code. The workqueue code requires the flag
TIMER_IRQSAFE for synchronisation purpose. This is not true for kthread's
delay timer since all operations occur under a lock.

Remove TIMER_IRQSAFE from the timer initialisation and use timer_setup()
for initialisation purpose which is the official function.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lkml.kernel.org/r/20190212162554.19779-2-bigeasy@linutronix.de

include/linux/kthread.h

@@ -164,9 +164,8 @@ extern void __kthread_init_worker(struct kthread_worker *worker,
 #define kthread_init_delayed_work(dwork, fn)				\
 	do {								\
 		kthread_init_work(&(dwork)->work, (fn));		\
-		__init_timer(&(dwork)->timer,				\
-			     kthread_delayed_work_timer_fn,		\
-			     TIMER_IRQSAFE);				\
+		timer_setup(&(dwork)->timer,				\
+			     kthread_delayed_work_timer_fn, 0);		\
 	} while (0)
 
 int kthread_worker_fn(void *worker_ptr);

kernel/kthread.c

@@ -835,6 +835,7 @@ void kthread_delayed_work_timer_fn(struct timer_list *t)
 	struct kthread_delayed_work *dwork = from_timer(dwork, t, timer);
 	struct kthread_work *work = &dwork->work;
 	struct kthread_worker *worker = work->worker;
+	unsigned long flags;
 
 	/*
 	 * This might happen when a pending work is reinitialized.
@@ -843,7 +844,7 @@ void kthread_delayed_work_timer_fn(struct timer_list *t)
 	if (WARN_ON_ONCE(!worker))
 		return;
 
-	raw_spin_lock(&worker->lock);
+	raw_spin_lock_irqsave(&worker->lock, flags);
 	/* Work must not be used with >1 worker, see kthread_queue_work(). */
 	WARN_ON_ONCE(work->worker != worker);
 
@@ -852,7 +853,7 @@ void kthread_delayed_work_timer_fn(struct timer_list *t)
 	list_del_init(&work->node);
 	kthread_insert_work(worker, work, &worker->work_list);
 
-	raw_spin_unlock(&worker->lock);
+	raw_spin_unlock_irqrestore(&worker->lock, flags);
 }
 EXPORT_SYMBOL(kthread_delayed_work_timer_fn);