Commit 9e8cd2f5 authored by Tejun Heo's avatar Tejun Heo

workqueue: implement apply_workqueue_attrs()

Implement apply_workqueue_attrs() which applies workqueue_attrs to the
specified unbound workqueue by creating a new pwq (pool_workqueue)
linked to worker_pool with the specified attributes.

A new pwq is linked at the head of wq->pwqs instead of tail and
__queue_work() verifies that the first unbound pwq has positive refcnt
before choosing it for the actual queueing.  This is to cover the case
where creation of a new pwq races with queueing.  As base ref on a pwq
won't be dropped without making another pwq the first one,
__queue_work() is guaranteed to make progress and not add work item to
a dead pwq.

init_and_link_pwq() is updated to return the last first pwq the new
pwq replaced, which is put by apply_workqueue_attrs().

Note that apply_workqueue_attrs() is almost identical to unbound pwq
part of alloc_and_link_pwqs().  The only difference is that there is
no previous first pwq.  apply_workqueue_attrs() is implemented to
handle such cases and replaces unbound pwq handling in
alloc_and_link_pwqs().
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
parent c9178087
......@@ -410,6 +410,8 @@ extern void destroy_workqueue(struct workqueue_struct *wq);
struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask);
void free_workqueue_attrs(struct workqueue_attrs *attrs);
int apply_workqueue_attrs(struct workqueue_struct *wq,
const struct workqueue_attrs *attrs);
extern bool queue_work_on(int cpu, struct workqueue_struct *wq,
struct work_struct *work);
......
......@@ -1228,7 +1228,7 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
if (unlikely(wq->flags & WQ_DRAINING) &&
WARN_ON_ONCE(!is_chained_work(wq)))
return;
retry:
/* pwq which will be used unless @work is executing elsewhere */
if (!(wq->flags & WQ_UNBOUND)) {
if (cpu == WORK_CPU_UNBOUND)
......@@ -1262,6 +1262,25 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
spin_lock(&pwq->pool->lock);
}
/*
* pwq is determined and locked. For unbound pools, we could have
* raced with pwq release and it could already be dead. If its
* refcnt is zero, repeat pwq selection. Note that pwqs never die
* without another pwq replacing it as the first pwq or while a
* work item is executing on it, so the retying is guaranteed to
* make forward-progress.
*/
if (unlikely(!pwq->refcnt)) {
if (wq->flags & WQ_UNBOUND) {
spin_unlock(&pwq->pool->lock);
cpu_relax();
goto retry;
}
/* oops */
WARN_ONCE(true, "workqueue: per-cpu pwq for %s on cpu%d has 0 refcnt",
wq->name, cpu);
}
/* pwq determined, queue */
trace_workqueue_queue_work(req_cpu, pwq, work);
......@@ -3425,7 +3444,8 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
static void init_and_link_pwq(struct pool_workqueue *pwq,
struct workqueue_struct *wq,
struct worker_pool *pool)
struct worker_pool *pool,
struct pool_workqueue **p_last_pwq)
{
BUG_ON((unsigned long)pwq & WORK_STRUCT_FLAG_MASK);
......@@ -3445,13 +3465,58 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
mutex_lock(&wq->flush_mutex);
spin_lock_irq(&workqueue_lock);
if (p_last_pwq)
*p_last_pwq = first_pwq(wq);
pwq->work_color = wq->work_color;
list_add_tail_rcu(&pwq->pwqs_node, &wq->pwqs);
list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
spin_unlock_irq(&workqueue_lock);
mutex_unlock(&wq->flush_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. If @attrs doesn't match the
* current attributes, a new pwq is created and made the first pwq which
* will serve all new work items. 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. Returns 0 on success and -errno on
* failure.
*/
int apply_workqueue_attrs(struct workqueue_struct *wq,
const struct workqueue_attrs *attrs)
{
struct pool_workqueue *pwq, *last_pwq;
struct worker_pool *pool;
if (WARN_ON(!(wq->flags & WQ_UNBOUND)))
return -EINVAL;
pwq = kmem_cache_zalloc(pwq_cache, GFP_KERNEL);
if (!pwq)
return -ENOMEM;
pool = get_unbound_pool(attrs);
if (!pool) {
kmem_cache_free(pwq_cache, pwq);
return -ENOMEM;
}
init_and_link_pwq(pwq, wq, pool, &last_pwq);
if (last_pwq) {
spin_lock_irq(&last_pwq->pool->lock);
put_pwq(last_pwq);
spin_unlock_irq(&last_pwq->pool->lock);
}
return 0;
}
static int alloc_and_link_pwqs(struct workqueue_struct *wq)
{
bool highpri = wq->flags & WQ_HIGHPRI;
......@@ -3468,26 +3533,12 @@ static int alloc_and_link_pwqs(struct workqueue_struct *wq)
struct worker_pool *cpu_pools =
per_cpu(cpu_worker_pools, cpu);
init_and_link_pwq(pwq, wq, &cpu_pools[highpri]);
init_and_link_pwq(pwq, wq, &cpu_pools[highpri], NULL);
}
return 0;
} else {
struct pool_workqueue *pwq;
struct worker_pool *pool;
pwq = kmem_cache_zalloc(pwq_cache, GFP_KERNEL);
if (!pwq)
return -ENOMEM;
pool = get_unbound_pool(unbound_std_wq_attrs[highpri]);
if (!pool) {
kmem_cache_free(pwq_cache, pwq);
return -ENOMEM;
}
init_and_link_pwq(pwq, wq, pool);
return apply_workqueue_attrs(wq, unbound_std_wq_attrs[highpri]);
}
return 0;
}
static int wq_clamp_max_active(int max_active, unsigned int flags,
......
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