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Commit de5b55c1 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

stop_machine: Use raw spinlocks 



Use raw-locks in stop_machine() to allow locking in irq-off and
preempt-disabled regions on -RT. This also documents the possible locking
context in general.

[bigeasy: update patch description.]
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lkml.kernel.org/r/20180423191635.6014-1-bigeasy@linutronix.de
parent 02acc80d

kernel/stop_machine.c

+12 −12
Original line number Diff line number Diff line
@@ -36,7 +36,7 @@ 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 */
@@ -78,13 +78,13 @@ static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work) 
	unsigned long flags;

	bool enabled;



	spin_lock_irqsave(&stopper->lock, flags);

	raw_spin_lock_irqsave(&stopper->lock, flags);

	enabled = stopper->enabled;

	if (enabled)

		__cpu_stop_queue_work(stopper, work);

	else if (work->done)

		cpu_stop_signal_done(work->done);

	spin_unlock_irqrestore(&stopper->lock, flags);

	raw_spin_unlock_irqrestore(&stopper->lock, flags);



	return enabled;

}
@@ -231,8 +231,8 @@ static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, 
	struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2);

	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)
@@ -255,8 +255,8 @@ static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1, 
	__cpu_stop_queue_work(stopper1, work1);

	__cpu_stop_queue_work(stopper2, work2);

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)
@@ -448,9 +448,9 @@ static int cpu_stop_should_run(unsigned int cpu) 
	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;

}
@@ -461,13 +461,13 @@ static void cpu_stopper_thread(unsigned int cpu) 


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;
@@ -541,7 +541,7 @@ 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);

	}