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Date: Wed, 20 Mar 2013 03:28:13 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Tejun Heo <tj@...nel.org>, linux-kernel@...r.kernel.org
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Subject: [PATCH 13/21] workqueue: remove unused pwq_lock
all first_pwq() and for_each_pwq() are converted to be protected by
wq->mutex or RCU_SCHED, so freaky pwq_lock is unused.
simply remove it.
Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
---
kernel/workqueue.c | 31 +++++++++++--------------------
1 files changed, 11 insertions(+), 20 deletions(-)
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index a3460e7..e45f038 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -127,12 +127,9 @@ enum {
*
* PR: pools_mutex protected for writes. Sched-RCU protected for reads.
*
- * PW: pwq_lock protected.
- *
* Q: wq->mutex protected.
*
- * QR: wq->mutex and pwq_lock protected for writes. Sched-RCU
- * protected for reads.
+ * QR: wq->mutex protected for writes. Sched-RCU protected for reads.
*
* MD: wq_mayday_lock protected.
*/
@@ -206,7 +203,7 @@ 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 pwq_lock.
+ * determined without grabbing wq->mutex.
*/
struct work_struct unbound_release_work;
struct rcu_head rcu;
@@ -260,7 +257,6 @@ static struct kmem_cache *pwq_cache;
static DEFINE_MUTEX(wqs_mutex); /* protects workqueues */
static DEFINE_MUTEX(pools_mutex); /* protects pools */
-static DEFINE_SPINLOCK(pwq_lock); /* protects pool_workqueues */
static DEFINE_SPINLOCK(wq_mayday_lock); /* protects wq->maydays list */
static LIST_HEAD(workqueues); /* QS: list of all workqueues */
@@ -301,11 +297,10 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
lockdep_is_held(&pools_mutex), \
"sched RCU or pools_mutex should be held")
-#define assert_rcu_or_pwq_lock(wq) \
+#define assert_rcu_or_wq_mutex(wq) \
rcu_lockdep_assert(rcu_read_lock_sched_held() || \
- lockdep_is_held(&wq->mutex) || \
- lockdep_is_held(&pwq_lock), \
- "sched RCU or pwq_lock should be held")
+ lockdep_is_held(&wq->mutex), \
+ "sched RCU or wq->mutex should be held")
#ifdef CONFIG_LOCKDEP
#define assert_manager_or_pool_lock(pool) \
@@ -359,7 +354,7 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
* @pwq: iteration cursor
* @wq: the target workqueue
*
- * This must be called either with pwq_lock held or sched RCU read locked.
+ * This must be called either with wq->mutex 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.
*
@@ -368,7 +363,7 @@ static void copy_workqueue_attrs(struct workqueue_attrs *to,
*/
#define for_each_pwq(pwq, wq) \
list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node) \
- if (({ assert_rcu_or_pwq_lock(wq); false; })) { } \
+ if (({ assert_rcu_or_wq_mutex(wq); false; })) { } \
else
#ifdef CONFIG_DEBUG_OBJECTS_WORK
@@ -507,13 +502,13 @@ 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 pwq_lock held or sched RCU read locked.
+ * This must be called either with wq->mutex 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_pwq_lock(wq);
+ assert_rcu_or_wq_mutex(wq);
return list_first_or_null_rcu(&wq->pwqs, struct pool_workqueue,
pwqs_node);
}
@@ -3551,9 +3546,7 @@ static void pwq_unbound_release_workfn(struct work_struct *work)
* and consistent with the linking path.
*/
mutex_lock(&wq->mutex);
- spin_lock_irq(&pwq_lock);
list_del_rcu(&pwq->pwqs_node);
- spin_unlock_irq(&pwq_lock);
mutex_unlock(&wq->mutex);
put_unbound_pool(pool);
@@ -3639,9 +3632,7 @@ static void init_and_link_pwq(struct pool_workqueue *pwq,
pwq_adjust_max_active(pwq);
/* link in @pwq */
- spin_lock_irq(&pwq_lock);
list_add_rcu(&pwq->pwqs_node, &wq->pwqs);
- spin_unlock_irq(&pwq_lock);
mutex_unlock(&wq->mutex);
}
@@ -4290,7 +4281,7 @@ EXPORT_SYMBOL_GPL(work_on_cpu);
* pool->worklist.
*
* CONTEXT:
- * Grabs and releases wqs_mutex, pwq_lock and pool->lock's.
+ * Grabs and releases wqs_mutex, wq->mutex and pool->lock's.
*/
void freeze_workqueues_begin(void)
{
@@ -4377,7 +4368,7 @@ out_unlock:
* frozen works are transferred to their respective pool worklists.
*
* CONTEXT:
- * Grabs and releases wqs_mutex, pwq_lock and pool->lock's.
+ * Grabs and releases wqs_mutex, wq->mutex and pool->lock's.
*/
void thaw_workqueues(void)
{
--
1.7.7.6
--
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