From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCHv2 11/11] writeback: prevent unnecessary bdi threads
 wakeups
Date: Thu, 22 Jul 2010 05:00:23 -0400
Message-ID: <20100722090023.GA7692@infradead.org>
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Cc: Artem Bityutskiy <dedekind1@gmail.com>,
	Dave Chinner <dchinner@redhat.com>,
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
	Jens Axboe <axboe@kernel.dk>
To: Dave Chinner <david@fromorbit.com>
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On Thu, Jul 22, 2010 at 10:41:55AM +1000, Dave Chinner wrote:
> 	if (wakeup_bdi) {
> 		trace_writeback_wakeup(bdi)
> 		spin_lock(&bdi->wb_lock);
> 		if (!bdi->wb.task) {{
> 			trace_writeback_wakeup_nothread(bdi);
> 			wake_up_process(default_backing_dev_info.wb.task);
> 		} else
> 			wake_up_process(bdi->wb.task);
> 		spin_unlock(&bdi->wb_lock);

That gives us duplicate traces for the first case, what about:

	 if (wakeup_bdi) {
	 	spin_lock(&bdi->wb_lock);
		if (bdi->wb.task) {
			trace_writeback_wake_thread(bdi);
			wake_up_process(bdi->wb.task);
		} else {
			trace_writeback_wake_forker_thread(bdi);
			wake_up_process(default_backing_dev_info.wb.task);
		}
		spin_unlock(&bdi->wb_lock);
	}