linux-kernel - Re: [PATCH] block: Avoid missed wakeup in request waitqueue

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Message-ID: <4FC42370.600@redhat.com>
Date:	Tue, 29 May 2012 09:16:32 +0800
From:	Asias He <asias@...hat.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: Avoid missed wakeup in request waitqueue

On 05/28/2012 06:26 PM, Tejun Heo wrote:
> On Mon, May 28, 2012 at 12:19:03PM +0800, Asias He wrote:
>> diff --git a/block/blk-core.c b/block/blk-core.c
>> index 1f61b74..1a45877 100644
>> --- a/block/blk-core.c
>> +++ b/block/blk-core.c
>> @@ -359,9 +359,10 @@ EXPORT_SYMBOL(blk_put_queue);
>>    */
>>   void blk_drain_queue(struct request_queue *q, bool drain_all)
>>   {
>> +	int i;
>> +
>>   	while (true) {
>>   		bool drain = false;
>> -		int i;
>>
>>   		spin_lock_irq(q->queue_lock);
>>
>> @@ -400,6 +401,14 @@ void blk_drain_queue(struct request_queue *q, bool drain_all)
>>   			break;
>>   		msleep(10);
>>   	}
>> +
>> +	/* Wake up threads which are sleeping on get_request() */
>> +	spin_lock_irq(q->queue_lock);
>> +	for (i = 0; i<  ARRAY_SIZE(q->rq.wait); i++) {
>> +		if (waitqueue_active(&q->rq.wait[i]))
>> +			wake_up_all(&q->rq.wait[i]);
>> +	}
>> +	spin_unlock_irq(q->queue_lock);
>
> I don't think we need waitqueue_active() optimization here.  Let's
> just do,
>
> 	/* please explain why this is necessary */
> 	for (i = 0; i<  ARRAY_SIZE(q->rq.wait); i++)
> 		wake_up_all(&q->rq.wait[i]);

OK. V2 is on its way.


-- 
Asias
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