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workqueue: separate out and refactor the locking of applying attrs

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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: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Lai Jiangshan 2015-05-19 18:03:47 +08:00 committed by Tejun Heo
parent f7142ed483
commit a0111cf671
1 changed files with 46 additions and 34 deletions
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80
kernel/workqueue.c
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@ -3621,6 +3621,46 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
mutex_unlock(&ctx->wq->mutex);
}
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;
int ret = -ENOMEM;
/* only unbound workqueues can change attributes */
if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
return -EINVAL;
/* creating multiple pwqs breaks ordering guarantee */
if (WARN_ON((wq->flags & __WQ_ORDERED) && !list_empty(&wq->pwqs)))
return -EINVAL;
ctx = apply_wqattrs_prepare(wq, attrs);
/* the ctx has been prepared successfully, let's commit it */
if (ctx) {
apply_wqattrs_commit(ctx);
ret = 0;
}
apply_wqattrs_cleanup(ctx);
return ret;
}
/**
* apply_workqueue_attrs - apply new workqueue_attrs to an unbound workqueue
* @wq: the target workqueue
@ -3640,37 +3680,11 @@ static void apply_wqattrs_commit(struct apply_wqattrs_ctx *ctx)
int apply_workqueue_attrs(struct workqueue_struct *wq,
const struct workqueue_attrs *attrs)
{
struct apply_wqattrs_ctx *ctx;
int ret = -ENOMEM;
int ret;
/* only unbound workqueues can change attributes */
if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
return -EINVAL;
/* creating multiple pwqs breaks ordering guarantee */
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 */
if (ctx) {
apply_wqattrs_commit(ctx);
ret = 0;
}
mutex_unlock(&wq_pool_mutex);
put_online_cpus();
apply_wqattrs_cleanup(ctx);
apply_wqattrs_lock();
ret = apply_workqueue_attrs_locked(wq, attrs);
apply_wqattrs_unlock();
return ret;
}
@ -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;