linux-kernel - Re: Disk spin down issue on shut down/suspend to disk

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Date:	Wed, 08 Aug 2007 11:54:53 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Michael Sedkowski <sedmich@...il.com>
CC:	trenn@...e.de, Robert Hancock <hancockr@...w.ca>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: Disk spin down issue on shut down/suspend to disk

Michael Sedkowski wrote:
> I did some additional checking today...
> On kernels prior to 2.6.22 line, the bug exists and manifests itself
> exactly the same way. However, when I removed the "-h" flag
> from /etc/init.d/halt, the drive spins down only once on "Power down"
> message and there is no sign of the bug and the emergency unload count
> remains constant. I've verified this on kernels 2.6.21.6; 2.6.20.4;
> 2.6.18-4-686-Etch.
> The obvious conclusion is that something must have changed it the 2.6.22
> kernels, so that removing the "-h" has no effect.
> I dunno if my observations are of any value, but I thought You should
> know...

Yeah, till 2.6.22, libata didn't spindown disks on suspend or power off
which incremented emergency unload count on all normal systems, so only
the ACPI S5 routine is spinning down the disk on you system.  The
problem here is that now that libata is fixed there are two entities
trying to spin down the disk and the disk is dumb enough to spin back up
when FLUSH CACHE or STANDBYNOW is received while spun down.  :-(

Thanks.

-- 
tejun
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