Commit f4b7b53c authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: Detach workers directly in idle_cull_fn() 



The code to kick off the destruction of workers is now in a process
context (idle_cull_fn()), and the detaching of a worker is not required
to be inside the worker thread now, so just do the detaching directly
in idle_cull_fn().

wake_dying_workers() is renamed to detach_dying_workers() and the unneeded
wakeup in wake_dying_workers() is also removed.

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 f45b1c3c

kernel/workqueue.c

+19 −26
Original line number Diff line number Diff line
@@ -2695,6 +2695,16 @@ static void unbind_worker(struct worker *worker) 
		WARN_ON_ONCE(set_cpus_allowed_ptr(worker->task, cpu_possible_mask) < 0);

}





static void detach_worker(struct worker *worker)

{

	lockdep_assert_held(&wq_pool_attach_mutex);



	unbind_worker(worker);

	list_del(&worker->node);

	worker->pool = NULL;

}



/**

 * worker_detach_from_pool() - detach a worker from its pool

 * @worker: worker which is attached to its pool
@@ -2711,11 +2721,7 @@ static void worker_detach_from_pool(struct worker *worker) 
	WARN_ON_ONCE(pool->flags & POOL_BH);



	mutex_lock(&wq_pool_attach_mutex);



	unbind_worker(worker);

	list_del(&worker->node);

	worker->pool = NULL;



	detach_worker(worker);

	mutex_unlock(&wq_pool_attach_mutex);



	/* clear leftover flags without pool->lock after it is detached */
@@ -2807,24 +2813,12 @@ static struct worker *create_worker(struct worker_pool *pool) 
	return NULL;

}



static void wake_dying_workers(struct list_head *cull_list)

static void detach_dying_workers(struct list_head *cull_list)

{

	struct worker *worker;



	list_for_each_entry(worker, cull_list, entry) {

		unbind_worker(worker);

		/*

		 * If the worker was somehow already running, then it had to be

		 * in pool->idle_list when set_worker_dying() happened or we

		 * wouldn't have gotten here.

		 *

		 * Thus, the worker must either have observed the WORKER_DIE

		 * flag, or have set its state to TASK_IDLE. Either way, the

		 * below will be observed by the worker and is safe to do

		 * outside of pool->lock.

		 */

		wake_up_process(worker->task);

	}

	list_for_each_entry(worker, cull_list, entry)

		detach_worker(worker);

}



static void reap_dying_workers(struct list_head *cull_list)
@@ -2930,9 +2924,9 @@ static void idle_cull_fn(struct work_struct *work) 


	/*

	 * Grabbing wq_pool_attach_mutex here ensures an already-running worker

	 * cannot proceed beyong worker_detach_from_pool() in its self-destruct

	 * path. This is required as a previously-preempted worker could run after

	 * set_worker_dying() has happened but before wake_dying_workers() did.

	 * cannot proceed beyong set_pf_worker() in its self-destruct path.

	 * This is required as a previously-preempted worker could run after

	 * set_worker_dying() has happened but before detach_dying_workers() did.

	 */

	mutex_lock(&wq_pool_attach_mutex);

	raw_spin_lock_irq(&pool->lock);
@@ -2953,7 +2947,7 @@ static void idle_cull_fn(struct work_struct *work) 
	}



	raw_spin_unlock_irq(&pool->lock);

	wake_dying_workers(&cull_list);

	detach_dying_workers(&cull_list);

	mutex_unlock(&wq_pool_attach_mutex);



	reap_dying_workers(&cull_list);
@@ -3336,7 +3330,6 @@ static int worker_thread(void *__worker) 


		set_task_comm(worker->task, "kworker/dying");

		ida_free(&pool->worker_ida, worker->id);

		worker_detach_from_pool(worker);

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

		return 0;

	}
@@ -4921,7 +4914,7 @@ static void put_unbound_pool(struct worker_pool *pool) 
	WARN_ON(pool->nr_workers || pool->nr_idle);

	raw_spin_unlock_irq(&pool->lock);



	wake_dying_workers(&cull_list);

	detach_dying_workers(&cull_list);



	mutex_unlock(&wq_pool_attach_mutex);