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Date: Tue, 29 May 2012 07:45:22 -0600
From: Tim Gardner <rtg.canonical@gmail.com>
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To: Asias He <asias@redhat.com>
CC: Jens Axboe <axboe@kernel.dk>, Tejun Heo <tj@kernel.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        tim.gardner@canonical.com
Subject: Re: [PATCH V3] block: Mitigate lock unbalance caused by lock switching
References: <20120528102214.GB15202@dhcp-172-17-108-109.mtv.corp.google.com> <1338255542-22247-1-git-send-email-asias@redhat.com>
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On 05/28/2012 07:39 PM, Asias He wrote:

<snip>

> @@ -440,6 +435,11 @@ void blk_cleanup_queue(struct request_queue *q)
>  	del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
>  	blk_sync_queue(q);
>  
> +	spin_lock_irq(lock);
> +	if (q->queue_lock != &q->__queue_lock)
> +		q->queue_lock = &q->__queue_lock;
> +	spin_unlock_irq(lock);
> +

Isn't the 'if' clause superfluous ? You could just do the assignment, e.g.,

+	spin_lock_irq(lock);
+	q->queue_lock = &q->__queue_lock;
+	spin_unlock_irq(lock);

rtg
-- 
Tim Gardner tim.gardner@canonical.com
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