linux-kernel - Re: [Bug #32982] Kernel locks up a few minutes after boot

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Date:	Tue, 19 Apr 2011 19:06:18 +0200
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Christoph Hellwig <hch@...radead.org>
CC:	Bart Van Assche <bvanassche@....org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Florian Mickler <florian@...kler.org>,
	Neil Brown <neilb@...e.de>
Subject: Re: [Bug #32982] Kernel locks up a few minutes after boot

On 2011-04-19 18:48, Christoph Hellwig wrote:
>> +		blk_run_queue_async(sdev->request_queue);
> 
> This doesn't even have to be async except when scsi drivers call
> cmd->scsi_done directly.  It seems like if this always went through the
> softirq (or kblockd) we could still run it in context for the others.

Exactly. I'll pass an 'optimize' patch past James.

>> +	/*
>> +	 * This get/put dance makes no sense
>> +	 */
>>  	get_device(&rport->dev);
>> -
>> -	spin_lock_irqsave(rport->rqst_q->queue_lock, flags);
>> -	flagset = test_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags) &&
>> -		  !test_bit(QUEUE_FLAG_REENTER, &rport->rqst_q->queue_flags);
>> -	if (flagset)
>> -		queue_flag_set(QUEUE_FLAG_REENTER, rport->rqst_q);
>> -	__blk_run_queue(rport->rqst_q);
>> -	if (flagset)
>> -		queue_flag_clear(QUEUE_FLAG_REENTER, rport->rqst_q);
>> -	spin_unlock_irqrestore(rport->rqst_q->queue_lock, flags);
>> -
>> +	blk_run_queue_async(rport->rqst_q);
> 
> And the QUEUE_FLAG_REENTER mess here never made sense either as it
> tested for a bit beeing set and not set at the same time.  So this one
> actually should be able to be replaced by a plain blk_run_queue.

Yep, it's completely broken as-is.

-- 
Jens Axboe

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