linux-kernel - Re: Linux 3.0 oopses when pulling a USB CDROM

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Date:	Mon, 4 Jul 2011 13:27:27 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	axboe@...nel.dk,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Andi Kleen <andi@...stfloor.org>,
	Dave Jones <davej@...hat.com>,
	SCSI development list <linux-scsi@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	USB list <linux-usb@...r.kernel.org>
Subject: Re: Linux 3.0 oopses when pulling a USB CDROM

On Sat, Jul 02, 2011 at 01:37:59PM -0400, Alan Stern wrote:
> The second bug, which hit me but apparently not any of you, is that the 
> request_queue's elevator gets deallocated while it is still in use.  
> That's because __scsi_remove_device() calls scsi_free_queue(), which 
> does blk_cleanup_queue(), which calls elevator_exit(), even though the 
> device file is still open and more requests will be submitted when the 
> file is closed.
> 
> I'm not sure of the right fix for this.  One possibility is to move the 
> scsi_free_queue() call to scsi_device_dev_release_usercontext().  Or 
> maybe the elevator_exit() call should be moved to blk_release_queue().
> 
> Also, I have no idea why this shows up with USB drives but not other 
> SCSI transports.  A fluke of timing?

FWIW, I reported a bug where the request_queue's elevator got deallocated
while it was still in use (fc transport with device hotplug):

http://www.spinics.net/lists/linux-scsi/msg52879.html
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