linux-kernel - Re: [BUGFIX 2/2] gdth: bugfix for the Timer at exit crash

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Message-Id: <1202924035.3109.48.camel@localhost.localdomain>
Date:	Wed, 13 Feb 2008 11:33:55 -0600
From:	James Bottomley <James.Bottomley@...senPartnership.com>
To:	Boaz Harrosh <bharrosh@...asas.com>
Cc:	Sven Köhler <skoehler@....de>,
	Christoph Hellwig <hch@...radead.org>,
	Jeff Garzik <jeff@...zik.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-kernel@...r.kernel.org, Joerg Dorchain <joerg@...chain.net>,
	Jon Chelton <jchelton@...global.com>,
	Stefan Priebe - allied internet ag 
	<s.priebe@...ied-internet.ag>
Subject: Re: [BUGFIX 2/2] gdth: bugfix for the Timer at exit crash

On Wed, 2008-02-13 at 19:18 +0200, Boaz Harrosh wrote:
> On Wed, Feb 13 2008 at 19:03 +0200, James Bottomley <James.Bottomley@...senPartnership.com> wrote:
> > It needs to register a reboot notifier, which gdth does.
> > 
> > However, the notifier is only called on reboot, so it also needs to
> > clean up correctly on module exit as well.
> > 
> > The alternative for GDTH would be to process the SCSI SYNCHRONIZE CACHE
> 
> Why would we think that the controller does not support this command
> is it not in the mandatory section of the standard?

Um, because the controller isn't a SCSI device.  It's an emulated device
which means the SCSI comands are processed in the driver.  It does look
like the driver<->HBA communication is some sort of translated dialect
of SCSI.

> > command.  That's done by a shutdown notifier from sd, so the correct
> > thing would always get done; however it does mean the driver has to be
> > in a condition to process the last sync cache command.
> 
> Why would it not be ready? what do other drivers do?
> The drivers is ready until the very last module's .exit. Is that good
> enough?

shutdown is called as part of device removal and module unload ...
usually from scsi_remove_host().  So you can't tear down command
processing before that point.

> > 
> > For the quick fix, just keep the current infrastructure and put back the
> > gdth_flush() command where it can be effective.
> > 
> 
> Just did. But if needed I would prefer to emulate the SCSI SYNCHRONIZE CACHE
> command and not that boot notifier thing. Please advise.

I think such a change, though desirable, would be too large to count as
a bug fix.

James


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