linux-kernel - Re: [PATCH v2.6.38-rc7] Revert "libata: ahci_start

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Date:	Fri, 20 May 2011 17:43:41 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Valdis.Kletnieks@...edu
Cc:	Jian Peng <jipeng2005@...il.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Jeff Garzik <jgarzik@...ox.com>,
	Michael Leun <lkml20100708@...ton.leun.net>,
	linux-ide@...r.kernel.org,
	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2.6.38-rc7] Revert "libata: ahci_start_engine
 compliant to AHCI spec"

On Fri, May 20, 2011 at 11:40:20AM -0400, Valdis.Kletnieks@...edu wrote:
> On Wed, 18 May 2011 17:14:56 PDT, Jian Peng said:
> 
> > > @@ -1353,6 +1332,8 @@
> > >
> > >
> > >   ahci_start_engine(ap);
> > >
> > > + msleep(5);
> > > +
> > >   if (online)
> > >
> > >    *class = ahci_dev_classify(ap);
> > >
> 
> It may very well be that adding a magic msleep(5) here just Makes It Work, but
> I have a gut feeling that it's in the wrong place (for starters, 'online' can't change
> during the msleep() unless somebody *else* sets it - in which case the locking
> is screwed up as we're not forcing a re-read of the value).  The msleep() probably
> needs to be before something else further down in the code (but I have no idea
> exactly what).

At this point, I think it would be better to simply add a flag and
enable the check for the affected controller.

Thanks.

-- 
tejun
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