linux-kernel - Re: Bug in SCSI async probing

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Date:	Tue, 26 May 2009 10:34:23 -0500
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	SCSI development list <linux-scsi@...r.kernel.org>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Bug in SCSI async probing

On Tue, 2009-05-26 at 11:22 -0400, Alan Stern wrote:
> James & Arjan:
> 
> Am I missing something here?  It looks like
> 
> 	fastboot: make scsi probes asynchronous
> 
> has introduced a bug in the sd probing code.  AFAICT, there is now
> nothing to prevent do_scan_async() from returning before
> sd_probe_async() has run.

True, but this isn't really a problem.

> Doesn't this mean that there's nothing to prevent sd_remove() from 
> being called and trying to unregister the disk _before_ 
> sd_probe_async() has managed to register it?

Yes, we've been discussing this ... most of the removal functions now
need async_synchronize calls to mitigate this type of race.

James


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