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Date: Wed, 13 Mar 2013 16:58:14 -0700
From: Tejun Heo <tj@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: laijs@...fujitsu.com, Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/6] workqueue: implement and use pwq_adjust_max_active()
Rename pwq_set_max_active() to pwq_adjust_max_active() and move
pool_workqueue->max_active synchronization and max_active
determination logic into it.
The new function should be called with workqueue_lock held for stable
workqueue->saved_max_active, determines the current max_active value
the target pool_workqueue should be using from @wq->saved_max_active
and the state of the associated pool, and applies it with proper
synchronization.
The current two users - workqueue_set_max_active() and
thaw_workqueues() - are updated accordingly. In addition, the manual
freezing handling in __alloc_workqueue_key() and
freeze_workqueues_begin() are replaced with calls to
pwq_adjust_max_active().
This centralizes max_active handling so that it's less error-prone.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/workqueue.c | 83 +++++++++++++++++++++++++-----------------------------
1 file changed, 38 insertions(+), 45 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index d519289..9e2ec4c 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -3726,23 +3726,38 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
}
/**
- * pwq_set_max_active - adjust max_active of a pwq
+ * pwq_adjust_max_active - update a pwq's max_active to the current setting
* @pwq: target pool_workqueue
- * @max_active: new max_active value.
- *
- * Set @pwq->max_active to @max_active and activate delayed works if
- * increased.
*
- * CONTEXT:
- * spin_lock_irq(pool->lock).
+ * If @pwq isn't freezing, set @pwq->max_active to the associated
+ * workqueue's saved_max_active and activate delayed work items
+ * accordingly. If @pwq is freezing, clear @pwq->max_active to zero.
*/
-static void pwq_set_max_active(struct pool_workqueue *pwq, int max_active)
+static void pwq_adjust_max_active(struct pool_workqueue *pwq)
{
- pwq->max_active = max_active;
+ struct workqueue_struct *wq = pwq->wq;
+ bool freezable = wq->flags & WQ_FREEZABLE;
+
+ /* for @wq->saved_max_active */
+ lockdep_assert_held(&workqueue_lock);
+
+ /* fast exit for non-freezable wqs */
+ if (!freezable && pwq->max_active == wq->saved_max_active)
+ return;
+
+ spin_lock(&pwq->pool->lock);
+
+ if (!freezable || !(pwq->pool->flags & POOL_FREEZING)) {
+ pwq->max_active = wq->saved_max_active;
- while (!list_empty(&pwq->delayed_works) &&
- pwq->nr_active < pwq->max_active)
- pwq_activate_first_delayed(pwq);
+ while (!list_empty(&pwq->delayed_works) &&
+ pwq->nr_active < pwq->max_active)
+ pwq_activate_first_delayed(pwq);
+ } else {
+ pwq->max_active = 0;
+ }
+
+ spin_unlock(&pwq->pool->lock);
}
static void init_and_link_pwq(struct pool_workqueue *pwq,
@@ -3932,15 +3947,14 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
goto err_destroy;
/*
- * workqueue_lock protects global freeze state and workqueues
- * list. Grab it, set max_active accordingly and add the new
- * workqueue to workqueues list.
+ * workqueue_lock protects global freeze state and workqueues list.
+ * Grab it, adjust max_active and add the new workqueue to
+ * workqueues list.
*/
spin_lock_irq(&workqueue_lock);
- if (workqueue_freezing && wq->flags & WQ_FREEZABLE)
- for_each_pwq(pwq, wq)
- pwq->max_active = 0;
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
list_add(&wq->list, &workqueues);
@@ -4055,17 +4069,8 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
wq->saved_max_active = max_active;
- for_each_pwq(pwq, wq) {
- struct worker_pool *pool = pwq->pool;
-
- spin_lock(&pool->lock);
-
- if (!(wq->flags & WQ_FREEZABLE) ||
- !(pool->flags & POOL_FREEZING))
- pwq_set_max_active(pwq, max_active);
-
- spin_unlock(&pool->lock);
- }
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
spin_unlock_irq(&workqueue_lock);
}
@@ -4358,14 +4363,8 @@ void freeze_workqueues_begin(void)
/* suppress further executions by setting max_active to zero */
list_for_each_entry(wq, &workqueues, list) {
- if (!(wq->flags & WQ_FREEZABLE))
- continue;
-
- for_each_pwq(pwq, wq) {
- spin_lock(&pwq->pool->lock);
- pwq->max_active = 0;
- spin_unlock(&pwq->pool->lock);
- }
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
}
spin_unlock_irq(&workqueue_lock);
@@ -4445,14 +4444,8 @@ void thaw_workqueues(void)
/* restore max_active and repopulate worklist */
list_for_each_entry(wq, &workqueues, list) {
- if (!(wq->flags & WQ_FREEZABLE))
- continue;
-
- for_each_pwq(pwq, wq) {
- spin_lock(&pwq->pool->lock);
- pwq_set_max_active(pwq, wq->saved_max_active);
- spin_unlock(&pwq->pool->lock);
- }
+ for_each_pwq(pwq, wq)
+ pwq_adjust_max_active(pwq);
}
/* kick workers */
--
1.8.1.4
--
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