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Date:	Fri, 04 Jul 2008 10:34:33 +0800
From:	Zhang Rui <rui.zhang@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	linux-pm <linux-pm@...ts.linux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>, harbour@...nx.od.ua
Subject: Re: [linux-pm] [PATCH 1/2] introduce new interface schedule_work_on


On Thu, 2008-07-03 at 22:04 +0800, Alan Stern wrote:
> On Thu, 3 Jul 2008, Zhang Rui wrote:
> 
> > This interface allows adding a job on a specific cpu.
> >
> > Although a work struct on a cpu will be scheduled to other cpu if the cpu dies,
> > there is a recursion if a work task tries to offline the cpu it's
> running on.
> > we need to schedule the task to a specific cpu in this case.
> > http://bugzilla.kernel.org/show_bug.cgi?id=10897
> >
> > Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> > Tested-by: Rus <harbour@...nx.od.ua>
> > ---
> >  include/linux/workqueue.h |    1 +
> >  kernel/workqueue.c        |   38
> ++++++++++++++++++++++++++++++++++++++
> >  2 files changed, 39 insertions(+)
> >
> > Index: linux-2.6/include/linux/workqueue.h
> > ===================================================================
> > --- linux-2.6.orig/include/linux/workqueue.h  2008-07-03
> 11:13:23.000000000 +0800
> > +++ linux-2.6/include/linux/workqueue.h       2008-07-03
> 11:13:25.000000000 +0800
> > @@ -188,6 +188,7 @@
> >  extern void flush_scheduled_work(void);
> > 
> >  extern int schedule_work(struct work_struct *work);
> > +extern int schedule_work_on(int cpu, struct work_struct *work);
> >  extern int schedule_delayed_work(struct delayed_work *work,
> unsigned long delay);
> >  extern int schedule_delayed_work_on(int cpu, struct delayed_work
> *work,
> >                                       unsigned long delay);
> 
> Is there some reason you don't export queue_work_on?  After all,
> queue_delayed_work_on is exported.

Both are okay. I didn't export it just because no one would use it
currently.
Please review the patch below.

thanks,
rui

Subject: introduce new interface schedule_work_on
This interface allows adding a job on a specific cpu.

Although a work struct on a cpu will be scheduled to other cpu if the cpu dies,
there is a recursion if a work task tries to offline the cpu it's running on.
we need to schedule the task to a specific cpu in this case.
http://bugzilla.kernel.org/show_bug.cgi?id=10897

Signed-off-by: Zhang Rui <rui.zhang@...el.com>
Tested-by: Rus <harbour@...nx.od.ua>
---
 include/linux/workqueue.h |    3 +++
 kernel/workqueue.c        |   39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+)

Index: linux-2.6/include/linux/workqueue.h
===================================================================
--- linux-2.6.orig/include/linux/workqueue.h	2007-05-04 10:57:08.000000000 +0800
+++ linux-2.6/include/linux/workqueue.h	2008-07-04 10:03:21.000000000 +0800
@@ -179,6 +179,8 @@
 extern void destroy_workqueue(struct workqueue_struct *wq);
 
 extern int queue_work(struct workqueue_struct *wq, struct work_struct *work);
+extern int queue_work_on(int cpu, struct workqueue_struct *wq,
+			struct work_struct *work);
 extern int queue_delayed_work(struct workqueue_struct *wq,
 			struct delayed_work *work, unsigned long delay);
 extern int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
@@ -188,6 +190,7 @@
 extern void flush_scheduled_work(void);
 
 extern int schedule_work(struct work_struct *work);
+extern int schedule_work_on(int cpu, struct work_struct *work);
 extern int schedule_delayed_work(struct delayed_work *work, unsigned long delay);
 extern int schedule_delayed_work_on(int cpu, struct delayed_work *work,
 					unsigned long delay);
Index: linux-2.6/kernel/workqueue.c
===================================================================
--- linux-2.6.orig/kernel/workqueue.c	2007-05-04 10:57:08.000000000 +0800
+++ linux-2.6/kernel/workqueue.c	2008-07-04 10:05:01.000000000 +0800
@@ -175,6 +175,32 @@
 }
 EXPORT_SYMBOL_GPL(queue_work);
 
+/**
+ * queue_work_on - queue work on specific cpu
+ * @cpu: CPU number to execute work on
+ * @wq: workqueue to use
+ * @work: work to queue
+ *
+ * Returns 0 if @work was already on a queue, non-zero otherwise.
+ *
+ * We queue the work to a specific CPU
+ */
+int
+queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
+{
+	int ret = 0;
+
+	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
+		BUG_ON(!list_empty(&work->entry));
+		preempt_disable();
+		__queue_work(wq_per_cpu(wq, cpu), work);
+		preempt_enable();
+		ret = 1;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(queue_work_on);
+
 static void delayed_work_timer_fn(unsigned long __data)
 {
 	struct delayed_work *dwork = (struct delayed_work *)__data;
@@ -553,6 +579,19 @@
 }
 EXPORT_SYMBOL(schedule_work);
 
+/*
+ * schedule_work_on - put work task on a specific cpu
+ * @cpu: cpu to put the work task on
+ * @work: job to be done
+ *
+ * This puts a job on a specific cpu
+ */
+int schedule_work_on(int cpu, struct work_struct *work)
+{
+	return queue_work_on(cpu, keventd_wq, work);
+}
+EXPORT_SYMBOL(schedule_work_on);
+
 /**
  * schedule_delayed_work - put work task in global workqueue after delay
  * @dwork: job to be done


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