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Commit a0111cf6 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Tejun Heo
Browse files

workqueue: separate out and refactor the locking of applying attrs 



Applying attrs requires two locks: get_online_cpus() and wq_pool_mutex,
and this code is duplicated at two places (apply_workqueue_attrs() and
workqueue_set_unbound_cpumask()).  So we separate out this locking
code into apply_wqattrs_[un]lock() and do a minor refactor on
apply_workqueue_attrs().

The apply_wqattrs_[un]lock() will be also used on later patch for
ensuring attrs changes are properly synchronized.

tj: minor updates to comments

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent f7142ed4

kernel/workqueue.c

+45 −33
Original line number Diff line number Diff line
@@ -3621,23 +3621,20 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx) 
	mutex_unlock(&ctx->wq->mutex);

}



/**

 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue

 * @wq: the target workqueue

 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()

 *

 * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA

 * machines, this function maps a separate pwq to each NUMA node with

 * possibles CPUs in @attrs->cpumask so that work items are affine to the

 * NUMA node it was issued on.  Older pwqs are released as in-flight work

 * items finish.  Note that a work item which repeatedly requeues itself

 * back-to-back will stay on its current pwq.

 *

 * Performs GFP_KERNEL allocations.

 *

 * Return: 0 on success and -errno on failure.

 */

int apply_workqueue_attrs(struct workqueue_struct *wq,

static void apply_wqattrs_lock(void)

{

	/* CPUs should stay stable across pwq creations and installations */

	get_online_cpus();

	mutex_lock(&wq_pool_mutex);

}



static void apply_wqattrs_unlock(void)

{

	mutex_unlock(&wq_pool_mutex);

	put_online_cpus();

}



static int apply_workqueue_attrs_locked(struct workqueue_struct *wq,

					const struct workqueue_attrs *attrs)

{

	struct apply_wqattrs_ctx *ctx;
@@ -3651,14 +3648,6 @@ int apply_workqueue_attrs(struct workqueue_struct *wq, 
	if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))

		return -EINVAL;



	/*

	 * CPUs should stay stable across pwq creations and installations.

	 * Pin CPUs, determine the target cpumask for each node and create

	 * pwqs accordingly.

	 */

	get_online_cpus();

	mutex_lock(&wq_pool_mutex);



	ctx = apply_wqattrs_prepare(wq, attrs);



	/* the ctx has been prepared successfully, let's commit it */
@@ -3667,14 +3656,39 @@ int apply_workqueue_attrs(struct workqueue_struct *wq, 
		ret = 0;

	}



	mutex_unlock(&wq_pool_mutex);

	put_online_cpus();



	apply_wqattrs_cleanup(ctx);



	return ret;

}



/**

 * apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue

 * @wq: the target workqueue

 * @attrs: the workqueue_attrs to apply, allocated with alloc_workqueue_attrs()

 *

 * Apply @attrs to an unbound workqueue @wq.  Unless disabled, on NUMA

 * machines, this function maps a separate pwq to each NUMA node with

 * possibles CPUs in @attrs->cpumask so that work items are affine to the

 * NUMA node it was issued on.  Older pwqs are released as in-flight work

 * items finish.  Note that a work item which repeatedly requeues itself

 * back-to-back will stay on its current pwq.

 *

 * Performs GFP_KERNEL allocations.

 *

 * Return: 0 on success and -errno on failure.

 */

int apply_workqueue_attrs(struct workqueue_struct *wq,

			  const struct workqueue_attrs *attrs)

{

	int ret;



	apply_wqattrs_lock();

	ret = apply_workqueue_attrs_locked(wq, attrs);

	apply_wqattrs_unlock();



	return ret;

}



/**

 * wq_update_unbound_numa - update NUMA affinity of a wq for CPU hot[un]plug

 * @wq: the target workqueue
@@ -4799,10 +4813,9 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) 
	if (!zalloc_cpumask_var(&saved_cpumask, GFP_KERNEL))

		return -ENOMEM;



	get_online_cpus();

	cpumask_and(cpumask, cpumask, cpu_possible_mask);

	if (!cpumask_empty(cpumask)) {

		mutex_lock(&wq_pool_mutex);

		apply_wqattrs_lock();



		/* save the old wq_unbound_cpumask. */

		cpumask_copy(saved_cpumask, wq_unbound_cpumask);
@@ -4815,9 +4828,8 @@ int workqueue_set_unbound_cpumask(cpumask_var_t cpumask) 
		if (ret < 0)

			cpumask_copy(wq_unbound_cpumask, saved_cpumask);



		mutex_unlock(&wq_pool_mutex);

		apply_wqattrs_unlock();

	}

	put_online_cpus();



	free_cpumask_var(saved_cpumask);

	return ret;