From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 29 Jun 2011 11:01:51 +0200
Subject: stop_machine: Use raw spinlocks
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git
Git-commit: 8012e0486008757412b17cdc90de10d317fbf06d
Patch-mainline: Queued in subsystem maintainer repository
References: SLE Realtime Extension

Use raw-locks in stomp_machine() to allow locking in irq-off regions.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Mike Galbraith <mgalbraith@suse.de>
---
 kernel/stop_machine.c |   34 +++++++++++++---------------------
 1 file changed, 13 insertions(+), 21 deletions(-)

--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -37,7 +37,7 @@ struct cpu_stop_done {
 struct cpu_stopper {
 	struct task_struct	*thread;
 
-	spinlock_t		lock;
+	raw_spinlock_t		lock;
 	bool			enabled;	/* is this stopper enabled? */
 	struct list_head	works;		/* list of pending works */
 
@@ -82,13 +82,13 @@ static bool cpu_stop_queue_work(unsigned
 	bool enabled;
 
 	preempt_disable();
-	spin_lock_irqsave(&stopper->lock, flags);
+	raw_spin_lock_irqsave(&stopper->lock, flags);
 	enabled = stopper->enabled;
 	if (enabled)
 		__cpu_stop_queue_work(stopper, work, &wakeq);
 	else if (work->done)
 		cpu_stop_signal_done(work->done);
-	spin_unlock_irqrestore(&stopper->lock, flags);
+	raw_spin_unlock_irqrestore(&stopper->lock, flags);
 
 	wake_up_q(&wakeq);
 	preempt_enable();
@@ -239,8 +239,8 @@ static int cpu_stop_queue_two_works(int
 	DEFINE_WAKE_Q(wakeq);
 	int err;
 retry:
-	spin_lock_irq(&stopper1->lock);
-	spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING);
+	raw_spin_lock_irq(&stopper1->lock);
+	raw_spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING);
 
 	err = -ENOENT;
 	if (!stopper1->enabled || !stopper2->enabled)
@@ -272,8 +272,8 @@ retry:
 	 */
 	preempt_disable();
 unlock:
-	spin_unlock(&stopper2->lock);
-	spin_unlock_irq(&stopper1->lock);
+	raw_spin_unlock(&stopper2->lock);
+	raw_spin_unlock_irq(&stopper1->lock);
 
 	if (unlikely(err == -EDEADLK)) {
 		while (stop_cpus_in_progress)
@@ -471,9 +471,9 @@ static int cpu_stop_should_run(unsigned
 	unsigned long flags;
 	int run;
 
-	spin_lock_irqsave(&stopper->lock, flags);
+	raw_spin_lock_irqsave(&stopper->lock, flags);
 	run = !list_empty(&stopper->works);
-	spin_unlock_irqrestore(&stopper->lock, flags);
+	raw_spin_unlock_irqrestore(&stopper->lock, flags);
 	return run;
 }
 
@@ -484,13 +484,13 @@ static void cpu_stopper_thread(unsigned
 
 repeat:
 	work = NULL;
-	spin_lock_irq(&stopper->lock);
+	raw_spin_lock_irq(&stopper->lock);
 	if (!list_empty(&stopper->works)) {
 		work = list_first_entry(&stopper->works,
 					struct cpu_stop_work, list);
 		list_del_init(&work->list);
 	}
-	spin_unlock_irq(&stopper->lock);
+	raw_spin_unlock_irq(&stopper->lock);
 
 	if (work) {
 		cpu_stop_fn_t fn = work->fn;
@@ -498,15 +498,7 @@ repeat:
 		struct cpu_stop_done *done = work->done;
 		int ret;
 
-		/*
-		 * Wait until the stopper finished scheduling on all
-		 * cpus
-		 */
-		lg_global_lock(&stop_cpus_lock);
-		/*
-		 * Let other cpu threads continue as well
-		 */
-		lg_global_unlock(&stop_cpus_lock);
+		/* XXX */
 
 		/* cpu stop callbacks must not sleep, make in_atomic() == T */
 		preempt_count_inc();
@@ -574,7 +566,7 @@ static int __init cpu_stop_init(void)
 	for_each_possible_cpu(cpu) {
 		struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
 
-		spin_lock_init(&stopper->lock);
+		raw_spin_lock_init(&stopper->lock);
 		INIT_LIST_HEAD(&stopper->works);
 	}