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Date: Wed, 13 Mar 2013 19:57:24 -0700
From: Tejun Heo <tj@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: laijs@...fujitsu.com, Tejun Heo <tj@...nel.org>
Subject: [PATCH 6/7] workqueue: separate out pool_workqueue locking into pwq_lock
This patch continues locking cleanup from the previous patch. It
breaks out pool_workqueue synchronization from workqueue_lock into a
new spinlock - pwq_lock. The followings are protected by pwq_lock.
* workqueue->pwqs
* workqueue->saved_max_active
The conversion is straight-forward. workqueue_lock usages which cover
the above two are converted to pwq_lock. New locking label PW added
for things protected by pwq_lock and FR is updated to mean flush_mutex
+ pwq_lock + sched-RCU.
This patch shouldn't introduce any visible behavior changes.
Signed-off-by: Tejun Heo <tj@...nel.org>
---
kernel/workqueue.c | 69 ++++++++++++++++++++++++++++--------------------------
1 file changed, 36 insertions(+), 33 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index c3b59ff..63856df 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -123,9 +123,11 @@ enum {
*
* WR: wq_mutex protected for writes. Sched-RCU protected for reads.
*
+ * PW: pwq_lock protected.
+ *
* W: workqueue_lock protected.
*
- * FR: wq->flush_mutex and workqueue_lock protected for writes. Sched-RCU
+ * FR: wq->flush_mutex and pwq_lock protected for writes. Sched-RCU
* protected for reads.
*/
@@ -198,7 +200,7 @@ struct pool_workqueue {
* Release of unbound pwq is punted to system_wq. See put_pwq()
* and pwq_unbound_release_workfn() for details. pool_workqueue
* itself is also sched-RCU protected so that the first pwq can be
- * determined without grabbing workqueue_lock.
+ * determined without grabbing pwq_lock.
*/
struct work_struct unbound_release_work;
struct rcu_head rcu;
@@ -237,7 +239,7 @@ struct workqueue_struct {
struct worker *rescuer; /* I: rescue worker */
int nr_drainers; /* WQ: drain in progress */
- int saved_max_active; /* W: saved pwq max_active */
+ int saved_max_active; /* PW: saved pwq max_active */
#ifdef CONFIG_SYSFS
struct wq_device *wq_dev; /* I: for sysfs interface */
@@ -251,6 +253,7 @@ struct workqueue_struct {
static struct kmem_cache *pwq_cache;
static DEFINE_MUTEX(wq_mutex); /* protects workqueues and pools */
+static DEFINE_SPINLOCK(pwq_lock); /* protects pool_workqueues */
static DEFINE_SPINLOCK(workqueue_lock);
static LIST_HEAD(workqueues); /* WQ: list of all workqueues */
@@ -291,10 +294,10 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
lockdep_is_held(&wq_mutex), \
"sched RCU or wq_mutex should be held")
-#define assert_rcu_or_wq_lock() \
+#define assert_rcu_or_pwq_lock() \
rcu_lockdep_assert(rcu_read_lock_sched_held() || \
- lockdep_is_held(&workqueue_lock), \
- "sched RCU or workqueue lock should be held")
+ lockdep_is_held(&pwq_lock), \
+ "sched RCU or pwq_lock should be held")
#define for_each_cpu_worker_pool(pool, cpu) \
for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0]; \
@@ -326,16 +329,16 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
* @pwq: iteration cursor
* @wq: the target workqueue
*
- * This must be called either with workqueue_lock held or sched RCU read
- * locked. If the pwq needs to be used beyond the locking in effect, the
- * caller is responsible for guaranteeing that the pwq stays online.
+ * This must be called either with pwq_lock held or sched RCU read locked.
+ * If the pwq needs to be used beyond the locking in effect, the caller is
+ * responsible for guaranteeing that the pwq stays online.
*
* The if/else clause exists only for the lockdep assertion and can be
* ignored.
*/
#define for_each_pwq(pwq, wq) \
list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
- if (({ assert_rcu_or_wq_lock(); false; })) { } \
+ if (({ assert_rcu_or_pwq_lock(); false; })) { } \
else
#ifdef CONFIG_DEBUG_OBJECTS_WORK
@@ -474,13 +477,13 @@ static int worker_pool_assign_id(struct worker_pool *pool)
* first_pwq - return the first pool_workqueue of the specified workqueue
* @wq: the target workqueue
*
- * This must be called either with workqueue_lock held or sched RCU read
- * locked. If the pwq needs to be used beyond the locking in effect, the
- * caller is responsible for guaranteeing that the pwq stays online.
+ * This must be called either with pwq_lock held or sched RCU read locked.
+ * If the pwq needs to be used beyond the locking in effect, the caller is
+ * responsible for guaranteeing that the pwq stays online.
*/
static struct pool_workqueue *first_pwq(struct workqueue_struct *wq)
{
- assert_rcu_or_wq_lock();
+ assert_rcu_or_pwq_lock();
return list_first_or_null_rcu(&wq->pwqs, struct pool_workqueue,
pwqs_node);
}
@@ -3639,9 +3642,9 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
* and consistent with the linking path.
*/
mutex_lock(&wq->flush_mutex);
- spin_lock_irq(&workqueue_lock);
+ spin_lock_irq(&pwq_lock);
list_del_rcu(&pwq->pwqs_node);
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
mutex_unlock(&wq->flush_mutex);
put_unbound_pool(pool);
@@ -3669,7 +3672,7 @@ static void pwq_adjust_max_active(struct pool_workqueue *pwq)
bool freezable = wq->flags & WQ_FREEZABLE;
/* for @wq->saved_max_active */
- lockdep_assert_held(&workqueue_lock);
+ lockdep_assert_held(&pwq_lock);
/* fast exit for non-freezable wqs */
if (!freezable && pwq->max_active == wq->saved_max_active)
@@ -3706,7 +3709,7 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
INIT_WORK(&pwq->unbound_release_work, pwq_unbound_release_workfn);
mutex_lock(&wq->flush_mutex);
- spin_lock_irq(&workqueue_lock);
+ spin_lock_irq(&pwq_lock);
/*
* Set the matching work_color. This is synchronized with
@@ -3722,7 +3725,7 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
/* link in @pwq */
list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
mutex_unlock(&wq->flush_mutex);
}
@@ -3886,10 +3889,10 @@ struct workqueue_struct *__alloc_workqueue_key(const char *fmt,
*/
mutex_lock(&wq_mutex);
- spin_lock_irq(&workqueue_lock);
+ spin_lock_irq(&pwq_lock);
for_each_pwq(pwq, wq)
pwq_adjust_max_active(pwq);
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
list_add(&wq->list, &workqueues);
@@ -3920,13 +3923,13 @@ void destroy_workqueue(struct workqueue_struct *wq)
drain_workqueue(wq);
/* sanity checks */
- spin_lock_irq(&workqueue_lock);
+ spin_lock_irq(&pwq_lock);
for_each_pwq(pwq, wq) {
int i;
for (i = 0; i < WORK_NR_COLORS; i++) {
if (WARN_ON(pwq->nr_in_flight[i])) {
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
return;
}
}
@@ -3934,11 +3937,11 @@ void destroy_workqueue(struct workqueue_struct *wq)
if (WARN_ON(pwq->refcnt > 1) ||
WARN_ON(pwq->nr_active) ||
WARN_ON(!list_empty(&pwq->delayed_works))) {
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
return;
}
}
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
/*
* wq list is used to freeze wq, remove from list after
@@ -4000,14 +4003,14 @@ void workqueue_set_max_active(struct workqueue_struct *wq, int max_active)
max_active = wq_clamp_max_active(max_active, wq->flags, wq->name);
- spin_lock_irq(&workqueue_lock);
+ spin_lock_irq(&pwq_lock);
wq->saved_max_active = max_active;
for_each_pwq(pwq, wq)
pwq_adjust_max_active(pwq);
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
}
EXPORT_SYMBOL_GPL(workqueue_set_max_active);
@@ -4266,7 +4269,7 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
* pool->worklist.
*
* CONTEXT:
- * Grabs and releases wq_mutex, workqueue_lock and pool->lock's.
+ * Grabs and releases wq_mutex, pwq_lock and pool->lock's.
*/
void freeze_workqueues_begin(void)
{
@@ -4289,12 +4292,12 @@ void freeze_workqueues_begin(void)
}
/* suppress further executions by setting max_active to zero */
- spin_lock_irq(&workqueue_lock);
+ spin_lock_irq(&pwq_lock);
list_for_each_entry(wq, &workqueues, list) {
for_each_pwq(pwq, wq)
pwq_adjust_max_active(pwq);
}
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
mutex_unlock(&wq_mutex);
}
@@ -4352,7 +4355,7 @@ out_unlock:
* frozen works are transferred to their respective pool worklists.
*
* CONTEXT:
- * Grabs and releases wq_mutex, workqueue_lock and pool->lock's.
+ * Grabs and releases wq_mutex, pwq_lock and pool->lock's.
*/
void thaw_workqueues(void)
{
@@ -4375,12 +4378,12 @@ void thaw_workqueues(void)
}
/* restore max_active and repopulate worklist */
- spin_lock_irq(&workqueue_lock);
+ spin_lock_irq(&pwq_lock);
list_for_each_entry(wq, &workqueues, list) {
for_each_pwq(pwq, wq)
pwq_adjust_max_active(pwq);
}
- spin_unlock_irq(&workqueue_lock);
+ spin_unlock_irq(&pwq_lock);
/* kick workers */
for_each_pool(pool, pi) {
--
1.8.1.4
--
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