Commit 68f83057 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: Reap workers via kthread_stop() and remove detach_completion 



The code to kick off the destruction of workers is now in a process
context (idle_cull_fn()), so kthread_stop() can be used in the process
context to replace the work of pool->detach_completion.

The wakeup in wake_dying_workers() is unneeded after this change, but it
is harmless, jut keep it here until next patch renames wake_dying_workers()
rather than renaming it again and again.

Cc: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: default avatarLai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent b56c7207

kernel/workqueue.c

+19 −16
Original line number Diff line number Diff line
@@ -216,7 +216,6 @@ struct worker_pool { 
	struct worker		*manager;	/* L: purely informational */

	struct list_head	workers;	/* A: attached workers */

	struct list_head        dying_workers;  /* A: workers about to die */

	struct completion	*detach_completion; /* all workers detached */



	struct ida		worker_ida;	/* worker IDs for task name */
@@ -2696,7 +2695,6 @@ static void worker_attach_to_pool(struct worker *worker, 
static void worker_detach_from_pool(struct worker *worker)

{

	struct worker_pool *pool = worker->pool;

	struct completion *detach_completion = NULL;



	/* there is one permanent BH worker per CPU which should never detach */

	WARN_ON_ONCE(pool->flags & POOL_BH);
@@ -2707,15 +2705,10 @@ static void worker_detach_from_pool(struct worker *worker) 
	list_del(&worker->node);

	worker->pool = NULL;



	if (list_empty(&pool->workers) && list_empty(&pool->dying_workers))

		detach_completion = pool->detach_completion;

	mutex_unlock(&wq_pool_attach_mutex);



	/* clear leftover flags without pool->lock after it is detached */

	worker->flags &= ~(WORKER_UNBOUND | WORKER_REBOUND);



	if (detach_completion)

		complete(detach_completion);

}



/**
@@ -2816,10 +2809,9 @@ static void unbind_worker(struct worker *worker) 


static void wake_dying_workers(struct list_head *cull_list)

{

	struct worker *worker, *tmp;

	struct worker *worker;



	list_for_each_entry_safe(worker, tmp, cull_list, entry) {

		list_del_init(&worker->entry);

	list_for_each_entry(worker, cull_list, entry) {

		unbind_worker(worker);

		/*

		 * If the worker was somehow already running, then it had to be
@@ -2835,6 +2827,17 @@ static void wake_dying_workers(struct list_head *cull_list) 
	}

}



static void reap_dying_workers(struct list_head *cull_list)

{

	struct worker *worker, *tmp;



	list_for_each_entry_safe(worker, tmp, cull_list, entry) {

		list_del_init(&worker->entry);

		kthread_stop_put(worker->task);

		kfree(worker);

	}

}



/**

 * set_worker_dying - Tag a worker for destruction

 * @worker: worker to be destroyed
@@ -2866,6 +2869,9 @@ static void set_worker_dying(struct worker *worker, struct list_head *list) 


	list_move(&worker->entry, list);

	list_move(&worker->node, &pool->dying_workers);



	/* get an extra task struct reference for later kthread_stop_put() */

	get_task_struct(worker->task);

}



/**
@@ -2949,6 +2955,8 @@ static void idle_cull_fn(struct work_struct *work) 
	raw_spin_unlock_irq(&pool->lock);

	wake_dying_workers(&cull_list);

	mutex_unlock(&wq_pool_attach_mutex);



	reap_dying_workers(&cull_list);

}



static void send_mayday(struct work_struct *work)
@@ -3330,7 +3338,6 @@ static int worker_thread(void *__worker) 
		ida_free(&pool->worker_ida, worker->id);

		worker_detach_from_pool(worker);

		WARN_ON_ONCE(!list_empty(&worker->entry));

		kfree(worker);

		return 0;

	}
@@ -4863,7 +4870,6 @@ static void rcu_free_pool(struct rcu_head *rcu) 
 */

static void put_unbound_pool(struct worker_pool *pool)

{

	DECLARE_COMPLETION_ONSTACK(detach_completion);

	struct worker *worker;

	LIST_HEAD(cull_list);
@@ -4917,12 +4923,9 @@ static void put_unbound_pool(struct worker_pool *pool) 


	wake_dying_workers(&cull_list);



	if (!list_empty(&pool->workers) || !list_empty(&pool->dying_workers))

		pool->detach_completion = &detach_completion;

	mutex_unlock(&wq_pool_attach_mutex);



	if (pool->detach_completion)

		wait_for_completion(pool->detach_completion);

	reap_dying_workers(&cull_list);



	/* shut down the timers */

	del_timer_sync(&pool->idle_timer);