From cd549687a7ee5e619a26f55af4059c4ae585811c Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 13 Mar 2013 19:47:39 -0700 Subject: [PATCH] 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: Tejun Heo --- kernel/workqueue.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index cac710646cbc..ce1ab069c5fe 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -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 */