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-rw-r--r--kernel/workqueue.c37
1 files changed, 15 insertions, 22 deletions
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 160fdc6e839a..1070b21ba4aa 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -68,6 +68,7 @@ enum {
* attach_mutex to avoid changing binding state while
* worker_attach_to_pool() is in progress.
*/
+ POOL_MANAGER_ACTIVE = 1 << 0, /* being managed */
POOL_DISASSOCIATED = 1 << 2, /* cpu can't serve workers */
/* worker flags */
@@ -165,7 +166,6 @@ struct worker_pool {
/* L: hash of busy workers */
/* see manage_workers() for details on the two manager mutexes */
- struct mutex manager_arb; /* manager arbitration */
struct worker *manager; /* L: purely informational */
struct mutex attach_mutex; /* attach/detach exclusion */
struct list_head workers; /* A: attached workers */
@@ -299,6 +299,7 @@ static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
static DEFINE_MUTEX(wq_pool_mutex); /* protects pools and workqueues list */
static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
+static DECLARE_WAIT_QUEUE_HEAD(wq_manager_wait); /* wait for manager to go away */
static LIST_HEAD(workqueues); /* PR: list of all workqueues */
static bool workqueue_freezing; /* PL: have wqs started freezing? */
@@ -801,7 +802,7 @@ static bool need_to_create_worker(struct worker_pool *pool)
/* Do we have too many workers and should some go away? */
static bool too_many_workers(struct worker_pool *pool)
{
- bool managing = mutex_is_locked(&pool->manager_arb);
+ bool managing = pool->flags & POOL_MANAGER_ACTIVE;
int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
int nr_busy = pool->nr_workers - nr_idle;
@@ -1980,24 +1981,17 @@ static bool manage_workers(struct worker *worker)
{
struct worker_pool *pool = worker->pool;
- /*
- * Anyone who successfully grabs manager_arb wins the arbitration
- * and becomes the manager. mutex_trylock() on pool->manager_arb
- * failure while holding pool->lock reliably indicates that someone
- * else is managing the pool and the worker which failed trylock
- * can proceed to executing work items. This means that anyone
- * grabbing manager_arb is responsible for actually performing
- * manager duties. If manager_arb is grabbed and released without
- * actual management, the pool may stall indefinitely.
- */
- if (!mutex_trylock(&pool->manager_arb))
+ if (pool->flags & POOL_MANAGER_ACTIVE)
return false;
+
+ pool->flags |= POOL_MANAGER_ACTIVE;
pool->manager = worker;
maybe_create_worker(pool);
pool->manager = NULL;
- mutex_unlock(&pool->manager_arb);
+ pool->flags &= ~POOL_MANAGER_ACTIVE;
+ wake_up(&wq_manager_wait);
return true;
}
@@ -3235,7 +3229,6 @@ static int init_worker_pool(struct worker_pool *pool)
setup_timer(&pool->mayday_timer, pool_mayday_timeout,
(unsigned long)pool);
- mutex_init(&pool->manager_arb);
mutex_init(&pool->attach_mutex);
INIT_LIST_HEAD(&pool->workers);
@@ -3305,13 +3298,15 @@ static void put_unbound_pool(struct worker_pool *pool)
hash_del(&pool->hash_node);
/*
- * Become the manager and destroy all workers. Grabbing
- * manager_arb prevents @pool's workers from blocking on
- * attach_mutex.
+ * Become the manager and destroy all workers. This prevents
+ * @pool's workers from blocking on attach_mutex. We're the last
+ * manager and @pool gets freed with the flag set.
*/
- mutex_lock(&pool->manager_arb);
-
spin_lock_irq(&pool->lock);
+ wait_event_lock_irq(wq_manager_wait,
+ !(pool->flags & POOL_MANAGER_ACTIVE), pool->lock);
+ pool->flags |= POOL_MANAGER_ACTIVE;
+
while ((worker = first_idle_worker(pool)))
destroy_worker(worker);
WARN_ON(pool->nr_workers || pool->nr_idle);
@@ -3325,8 +3320,6 @@ static void put_unbound_pool(struct worker_pool *pool)
if (pool->detach_completion)
wait_for_completion(pool->detach_completion);
- mutex_unlock(&pool->manager_arb);
-
/* shut down the timers */
del_timer_sync(&pool->idle_timer);
del_timer_sync(&pool->mayday_timer);