Commit cd549687 authored by Tejun Heo's avatar Tejun Heo
Browse files

workqueue: better define locking rules around worker creation / destruction 



When a manager creates or destroys workers, the operations are always
done with the manager_mutex held; however, initial worker creation or
worker destruction during pool release don't grab the mutex.  They are
still correct as initial worker creation doesn't require
synchronization and grabbing manager_arb provides enough exclusion for
pool release path.

Still, let's make everyone follow the same rules for consistency and
such that lockdep annotations can be added.

Update create_and_start_worker() and put_unbound_pool() to grab
manager_mutex around thread creation and destruction respectively and
add lockdep assertions to create_worker() and destroy_worker().

This patch doesn't introduce any visible behavior changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent ebf44d16

kernel/workqueue.c

+12 −1
Original line number Diff line number Diff line
@@ -1715,6 +1715,8 @@ static struct worker *create_worker(struct worker_pool *pool) 
	struct worker *worker = NULL;

	int id = -1;



	lockdep_assert_held(&pool->manager_mutex);



	spin_lock_irq(&pool->lock);

	while (ida_get_new(&pool->worker_ida, &id)) {

		spin_unlock_irq(&pool->lock);
@@ -1796,12 +1798,14 @@ static void start_worker(struct worker *worker) 
 * create_and_start_worker - create and start a worker for a pool

 * @pool: the target pool

 *

 * Create and start a new worker for @pool.

 * Grab the managership of @pool and create and start a new worker for it.

 */

static int create_and_start_worker(struct worker_pool *pool)

{

	struct worker *worker;



	mutex_lock(&pool->manager_mutex);



	worker = create_worker(pool);

	if (worker) {

		spin_lock_irq(&pool->lock);
@@ -1809,6 +1813,8 @@ static int create_and_start_worker(struct worker_pool *pool) 
		spin_unlock_irq(&pool->lock);

	}



	mutex_unlock(&pool->manager_mutex);



	return worker ? 0 : -ENOMEM;

}
@@ -1826,6 +1832,9 @@ static void destroy_worker(struct worker *worker) 
	struct worker_pool *pool = worker->pool;

	int id = worker->id;



	lockdep_assert_held(&pool->manager_mutex);

	lockdep_assert_held(&pool->lock);



	/* sanity check frenzy */

	if (WARN_ON(worker->current_work) ||

	    WARN_ON(!list_empty(&worker->scheduled)))
@@ -3531,6 +3540,7 @@ static void put_unbound_pool(struct worker_pool *pool) 
	 * manager_mutex.

	 */

	mutex_lock(&pool->manager_arb);

	mutex_lock(&pool->manager_mutex);

	spin_lock_irq(&pool->lock);



	while ((worker = first_worker(pool)))
@@ -3538,6 +3548,7 @@ static void put_unbound_pool(struct worker_pool *pool) 
	WARN_ON(pool->nr_workers || pool->nr_idle);



	spin_unlock_irq(&pool->lock);

	mutex_unlock(&pool->manager_mutex);

	mutex_unlock(&pool->manager_arb);



	/* shut down the timers */

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