linux-kernel - Re: [RFC][PATCH 14/16] writeback: move bdi threads exiting logic to the forker thread

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Date:	Tue, 20 Jul 2010 15:23:19 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 14/16] writeback: move bdi threads exiting logic
 to the forker thread

On Sun, 2010-07-18 at 03:02 -0400, Christoph Hellwig wrote:
> > +	if (wakeup_default) {
> >  		trace_writeback_nothread(bdi, work);
> >  		wake_up_process(default_backing_dev_info.wb.task);
> 
> Why not simply do the defaul thread wakeup under wb_lock, too?
> It keeps the code a lot simpler, and this is not a typical path anyway.

Will address.

> >  		if (dirty_writeback_interval) {
> > +			unsigned long wait_jiffies;
> > +
> >  			wait_jiffies = msecs_to_jiffies(dirty_writeback_interval * 10);
> >  			schedule_timeout(wait_jiffies);
> 
> No real need for a local variable here.

Will address.

> > @@ -364,7 +395,7 @@ static int bdi_forker_thread(void *ptr)
> >  		if (!list_empty(&me->bdi->work_list))
> >  			__set_current_state(TASK_RUNNING);
> >  
> > -		if (!fork) {
> > +		if (!fork && !kill) {
> 
> I think the code here would be a lot cleaner if you implement the
> suggestion I have for the forking restructuring.

As I replied earlier, to fork/kill the the thread from inside list walk
we'd need to drop the spinlock, which is not very nice. So I am keeping
this part intact so far.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)

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