linux-kernel - Re: 2.6.19-rc3-git7: scsi_device_unbusy: inconsistent lock state

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Date:	Mon, 30 Oct 2006 15:57:19 +0100
From:	Arjan van de Ven <arjan@...radead.org>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	Mark Lord <liml@....ca>,
	IDE/ATA development list <linux-ide@...r.kernel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>, mingo@...e.hu
Subject: Re: 2.6.19-rc3-git7: scsi_device_unbusy: inconsistent lock state


> which has always been considered safe, while not very pretty.


actually it's different I think (based on a brief inspection of the
code, I could well be wrong): 
get_request_wait() causes a get_request() call with a GFP_NOIO gfp_mask
which perculates upto cfq_set_request() as argument.
cfq_set_request() then calls the inline cfq_get_queue() (which isn't in
the backtrace due to inlining) which does
                } else if (gfp_mask & __GFP_WAIT) {
                        /* 
                         * Inform the allocator of the fact that we will
                         * just repeat this allocation if it fails, to allow
                         * the allocator to do whatever it needs to attempt to
                         * free memory.
                         */
                        spin_unlock_irq(cfqd->queue->queue_lock);

which enables interrupts right smack in the middle of holding a whole
bunch of locks.....

so to me it looks like lockdep at least has the appearance of moaning
about a reasonably fishy situation...



-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org


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