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Commit 4736cbf7 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: separate pool-attaching code out from create_worker() 



Currently, the code to attach a new worker to its pool is embedded in
create_worker().  Separating this code out will make the codes clearer
and will allow rescuers to share the code path later.

tj: Description and comment updates.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 92f9c5c4

kernel/workqueue.c

+38 −23
Original line number Diff line number Diff line
@@ -66,7 +66,7 @@ enum { 
	 *

	 * Note that DISASSOCIATED should be flipped only while holding

	 * attach_mutex to avoid changing binding state while

	 * create_worker() is in progress.

	 * worker_attach_to_pool() is in progress.

	 */

	POOL_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */

	POOL_FREEZING		= 1 << 3,	/* freeze in progress */
@@ -1682,14 +1682,47 @@ static struct worker *alloc_worker(void) 
	return worker;

}



/**

 * worker_attach_to_pool() - attach a worker to a pool

 * @worker: worker to be attached

 * @pool: the target pool

 *

 * Attach @worker to @pool.  Once attached, the %WORKER_UNBOUND flag and

 * cpu-binding of @worker are kept coordinated with the pool across

 * cpu-[un]hotplugs.

 */

static void worker_attach_to_pool(struct worker *worker,

				   struct worker_pool *pool)

{

	mutex_lock(&pool->attach_mutex);



	/*

	 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any

	 * online CPUs.  It'll be re-applied when any of the CPUs come up.

	 */

	set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);



	/*

	 * The pool->attach_mutex ensures %POOL_DISASSOCIATED remains

	 * stable across this function.  See the comments above the

	 * flag definition for details.

	 */

	if (pool->flags & POOL_DISASSOCIATED)

		worker->flags |= WORKER_UNBOUND;



	list_add_tail(&worker->node, &pool->workers);



	mutex_unlock(&pool->attach_mutex);

}



/**

 * worker_detach_from_pool() - detach a worker from its pool

 * @worker: worker which is attached to its pool

 * @pool: the pool @worker is attached to

 *

 * Undo the attaching which had been done in create_worker().  The caller

 * worker shouldn't access to the pool after detached except it has other

 * reference to the pool.

 * Undo the attaching which had been done in worker_attach_to_pool().  The

 * caller worker shouldn't access to the pool after detached except it has

 * other reference to the pool.

 */

static void worker_detach_from_pool(struct worker *worker,

				    struct worker_pool *pool)
@@ -1753,26 +1786,8 @@ static struct worker *create_worker(struct worker_pool *pool) 
	/* prevent userland from meddling with cpumask of workqueue workers */

	worker->task->flags |= PF_NO_SETAFFINITY;



	mutex_lock(&pool->attach_mutex);



	/*

	 * set_cpus_allowed_ptr() will fail if the cpumask doesn't have any

	 * online CPUs.  It'll be re-applied when any of the CPUs come up.

	 */

	set_cpus_allowed_ptr(worker->task, pool->attrs->cpumask);



	/*

	 * The pool->attach_mutex ensures %POOL_DISASSOCIATED

	 * remains stable across this function.  See the comments above the

	 * flag definition for details.

	 */

	if (pool->flags & POOL_DISASSOCIATED)

		worker->flags |= WORKER_UNBOUND;



	/* successful, attach the worker to the pool */

	list_add_tail(&worker->node, &pool->workers);



	mutex_unlock(&pool->attach_mutex);

	worker_attach_to_pool(worker, pool);



	return worker;