linux-kernel - Re: [PATCH 2/2] cciss: Fix SCSI device reset handler

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Date:	Tue, 2 Jun 2009 19:58:14 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	scameron@...rdog.cca.cpqcorp.net, linux-kernel@...r.kernel.org,
	linux-scsi@...r.kernel.org, mikem@...rdog.cca.cpqcorp.net
Subject: Re: [PATCH 2/2] cciss: Fix SCSI device reset handler

On Tue, Jun 02 2009, Andrew Morton wrote:
> On Tue, 2 Jun 2009 14:50:11 +0200
> Jens Axboe <jens.axboe@...cle.com> wrote:
> 
> > On Fri, May 29 2009, Andrew Morton wrote:
> > > On Wed, 27 May 2009 15:30:07 -0500
> > > scameron@...rdog.cca.cpqcorp.net wrote:
> > > 
> > > > +static int wait_for_device_to_become_ready(ctlr_info_t *h,
> > > > +	unsigned char lunaddr[])
> > > > +{
> > > > +	int rc;
> > > > +	int count = 0;
> > > > +	int waittime = HZ;
> > > > +	CommandList_struct *c;
> > > > +
> > > > +	c = cmd_alloc(h, 1);
> > > > +	if (!c) {
> > > > +		printk(KERN_WARNING "cciss%d: out of memory in "
> > > > +			"wait_for_device_to_become_ready.\n", h->ctlr);
> > > > +		return IO_ERROR;
> > > > +	}
> > > > +
> > > > +	/* Send test unit ready until device ready, or give up. */
> > > > +	while (count < 20) {
> > > > +
> > > > +		/* Wait for a bit.  do this first, because if we send
> > > > +		 * the TUR right away, the reset will just abort it.
> > > > +		 */
> > > > +		set_current_state(TASK_INTERRUPTIBLE);
> > > > +		schedule_timeout(waittime);
> > > 
> > > That's schedule_timeout_interruptible().
> > > 
> > > The problem with interruptible sleeps of this nature is that they are
> > > no-ops if the calling process happens to have signal_pending().  I
> > > suspect that this condition will break your driver.
> > > 
> > > If so, switching to schedule_timeout_uninterruptible() will unbreak it.
> > 
> > I added Stephens patch and your fixup.
> 
> My cciss-fix-scsi-device-reset-handler-fix.patch was a simple cleanup -
> it uses schedule_timeout_interruptible().
> 
> I believe that this should be changed to
> schedule_timeout_uninterruptible() for the above reasons, but the cciss
> guys fell asleep on me.

It's an improvement, none the less. And I bet it should just be
uninterruptible sleep, unless it has a good reason to accept signals.
Mike? Stephen?

-- 
Jens Axboe

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