destroy_worker() doesn't need to wait for worker's task exit.
There is no essential things to do after kthread_stop().
So we remove kthread_stop().
put_unbound_pool() needs to wait for workers' tasks exit.
we add a new completion to handle it.
The purpose of this patch is not making the slowpath destroy_worker()
faster, but:
1) allow destroy_worker() to be called in timeout handler in future patch.
2) reduce possible latency for create_worker()/cpu-hotplug.
Signed-off-by: Lai Jiangshan <la...@cn.fujitsu.com>
---
kernel/workqueue.c | 32 +++++++++++++++++---------------
1 files changed, 17 insertions(+), 15 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 743917d..6c38aed 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -170,6 +170,10 @@ struct worker_pool {
/*
* A worker is bound to the pool, it means:
* 1) the worker's cpumask is bound to the pool.
+ * 2) the worker gets a reference to the pool. The worker shouldn't
+ * access to the pool after the worker is unbound from the pool,
+ * except that the worker has another kinds of reference to
+ * the pool.
*
* bind_mutex is held in rescuer before processing works,
* so bind_mutex shouldn't have any directly nor indirecty dependency
@@ -177,6 +181,7 @@ struct worker_pool {
*/
struct mutex bind_mutex; /* workers binding */
struct list_head bind_list; /* B: bound workers*/
+ struct completion workers_leave; /* all workers exit */
struct workqueue_attrs *attrs; /* I: worker attributes */
struct hlist_node hash_node; /* PL: unbound_pool_hash node */
@@ -1668,9 +1673,15 @@ static void bind_worker(struct worker *worker, struct
worker_pool *pool)
static void unbind_worker(struct worker *worker, struct worker_pool *pool)
{
+ bool is_last;
+
mutex_lock(&pool->bind_mutex);
list_del(&worker->bind_entry);
+ is_last = list_empty(&worker->bind_entry);
mutex_unlock(&pool->bind_mutex);
+
+ if (is_last)
+ complete(&pool->workers_leave);
}
/**
@@ -1828,24 +1839,10 @@ static void destroy_worker(struct worker *worker)
if (worker->flags & WORKER_IDLE)
pool->nr_idle--;
- /*
- * Once WORKER_DIE is set, the kworker may destroy itself at any
- * point. Pin to ensure the task stays until we're done with it.
- */
- get_task_struct(worker->task);
-
list_del_init(&worker->entry);
worker->flags |= WORKER_DIE;
-
idr_remove(&pool->worker_idr, worker->id);
-
- spin_unlock_irq(&pool->lock);
-
- kthread_stop(worker->task);
- put_task_struct(worker->task);
- kfree(worker);
-
- spin_lock_irq(&pool->lock);
+ wake_up_process(worker->task);
}
static void idle_worker_timeout(unsigned long __pool)
@@ -2293,6 +2290,7 @@ woke_up:
worker->task->flags &= ~PF_WQ_WORKER;
unbind_worker(worker, pool);
+ kfree(worker);
return 0;
}
@@ -3529,6 +3527,7 @@ static int init_worker_pool(struct worker_pool *pool)
mutex_init(&pool->bind_mutex);
INIT_LIST_HEAD(&pool->bind_list);
+ init_completion(&pool->workers_leave);
INIT_HLIST_NODE(&pool->hash_node);
pool->refcnt = 1;
@@ -3588,6 +3587,7 @@ static void put_unbound_pool(struct worker_pool *pool)
mutex_lock(&pool->manager_mutex);
spin_lock_irq(&pool->lock);
+ WARN_ON(pool->nr_workers != pool->nr_idle);
while ((worker = first_worker(pool)))
destroy_worker(worker);
WARN_ON(pool->nr_workers || pool->nr_idle);
@@ -3596,6 +3596,8 @@ static void put_unbound_pool(struct worker_pool *pool)
mutex_unlock(&pool->manager_mutex);
mutex_unlock(&pool->manager_arb);
+ wait_for_completion(&pool->workers_leave);
+
/* shut down the timers */
del_timer_sync(&pool->idle_timer);
del_timer_sync(&pool->mayday_timer);
--
1.7.4.4
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