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From: Lai Jiangshan <laijs@cn.fujitsu.com>
To: Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Subject: [PATCH 04/12] workqueue: simplify is_chained_work()
Date: Thu, 27 Sep 2012 01:20:35 +0800	[thread overview]
Message-ID: <1348680043-5077-5-git-send-email-laijs@cn.fujitsu.com> (raw)
In-Reply-To: <1348680043-5077-1-git-send-email-laijs@cn.fujitsu.com>

is_chained_work() is too complicated. we can simply found out
whether current task is worker by PF_WQ_WORKER or wq->rescuer.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
 kernel/workqueue.c |   36 ++++++++++++------------------------
 1 files changed, 12 insertions(+), 24 deletions(-)

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index e41c562..c718b94 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -1182,34 +1182,22 @@ static void insert_work(struct cpu_workqueue_struct *cwq,
 
 /*
  * Test whether @work is being queued from another work executing on the
- * same workqueue.  This is rather expensive and should only be used from
- * cold paths.
+ * same workqueue.
  */
 static bool is_chained_work(struct workqueue_struct *wq)
 {
-	unsigned long flags;
-	unsigned int cpu;
+	struct worker *worker = NULL;
 
-	for_each_gcwq_cpu(cpu) {
-		struct global_cwq *gcwq = get_gcwq(cpu);
-		struct worker *worker;
-		struct hlist_node *pos;
-		int i;
+	if (wq->rescuer && current == wq->rescuer->task) /* rescuer_thread() */
+		worker = wq->rescuer;
+	else if (current->flags & PF_WQ_WORKER) /* worker_thread() */
+		worker = kthread_data(current);
 
-		spin_lock_irqsave(&gcwq->lock, flags);
-		for_each_busy_worker(worker, i, pos, gcwq) {
-			if (worker->task != current)
-				continue;
-			spin_unlock_irqrestore(&gcwq->lock, flags);
-			/*
-			 * I'm @worker, no locking necessary.  See if @work
-			 * is headed to the same workqueue.
-			 */
-			return worker->current_cwq->wq == wq;
-		}
-		spin_unlock_irqrestore(&gcwq->lock, flags);
-	}
-	return false;
+	/*
+	 * I'm @worker, no locking necessary.  See if @work
+	 * is headed to the same workqueue.
+	 */
+	return worker && worker->current_cwq->wq == wq;
 }
 
 static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
@@ -1231,7 +1219,7 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 
 	debug_work_activate(work);
 
-	/* if dying, only works from the same workqueue are allowed */
+	/* if draining, only works from the same workqueue are allowed */
 	if (unlikely(wq->flags & WQ_DRAINING) &&
 	    WARN_ON_ONCE(!is_chained_work(wq)))
 		return;
-- 
1.7.7.6


  parent reply	other threads:[~2012-09-26 17:21 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-09-26 17:20 [PATCH 00/12] workqueue: simple cleanups Lai Jiangshan
2012-09-26 17:20 ` [PATCH 01/12] workqueue: add WORKER_RESCUER Lai Jiangshan
2012-09-26 18:07   ` Tejun Heo
2012-09-28 10:11     ` Lai Jiangshan
2012-09-26 17:20 ` [PATCH 02/12] workqueue: disallow set_cpus_allowed_ptr() from work item Lai Jiangshan
2012-09-26 18:12   ` Tejun Heo
2012-09-26 17:20 ` [PATCH 03/12] workqueue: remove WORKER_PREP from rescuer Lai Jiangshan
2012-09-26 18:24   ` Tejun Heo
2012-09-28 10:04     ` Lai Jiangshan
2012-09-30  7:39       ` Tejun Heo
2012-09-26 17:20 ` Lai Jiangshan [this message]
2012-09-26 18:28   ` [PATCH 04/12] workqueue: simplify is_chained_work() Tejun Heo
2012-09-28  9:52     ` Lai Jiangshan
2012-09-30  7:32       ` Tejun Heo
2012-09-26 17:20 ` [PATCH 05/12] workqueue: don't wake up other workers in rescuer Lai Jiangshan
2012-09-26 18:34   ` Tejun Heo
2012-09-28 10:18     ` Lai Jiangshan
2012-09-26 17:20 ` [PATCH 06/12] workqueue: destroy_worker() can only destory idle worker not just created worker Lai Jiangshan
2012-09-26 18:35   ` Tejun Heo
2012-09-26 17:20 ` [PATCH 07/12] workqueue: remove WORKER_STARTED Lai Jiangshan
2012-09-26 18:36   ` Tejun Heo
2012-09-28  9:52     ` Lai Jiangshan
2012-09-26 17:20 ` [PATCH 08/12] workqueue: fix comments of insert_work() Lai Jiangshan
2012-09-26 17:20 ` [PATCH 09/12] workqueue: declare system_highpri_wq Lai Jiangshan
2012-09-26 17:20 ` [PATCH 10/12] cpu-hotplug.txt: fix comments of work_on_cpu() Lai Jiangshan
2012-09-26 17:20 ` [RFC PATCH 11/12] workqueue: add WQ_CPU_INTENSIVE to system_long_wq Lai Jiangshan
2012-09-26 18:38   ` Tejun Heo
2012-09-28  8:06     ` Lai Jiangshan
2012-09-30  7:22       ` Tejun Heo
2012-09-26 17:20 ` [PATCH 12/12] workqueue: avoid work_on_cpu() to interfere system_wq Lai Jiangshan

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