From: Rob Landley <rob@landley.net>
To: "Francesco Pretto" <ceztko@gmail.com>
Subject: Re: Weird hard disk noise on shutdown (bug #7674)
Date: Wed, 16 May 2007 19:47:35 -0400
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Cc: "Dave Jones" <davej@redhat.com>, "Tejun Heo" <htejun@gmail.com>,
       "Phillip Susi" <psusi@cfl.rr.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
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On Wednesday 16 May 2007 5:15 am, Francesco Pretto wrote:
> - everyone else:
> // continue to do nothing :-)
> reboot();

That would be cool, but the impression I got from 
http://linux-ata.org/shutdown.html was that shutdown commands were supposed 
to _add_ quiescing of drives in order to avoid emergency head parking on 
poweroff.

That article says:

> Distros should update their shutdown(8) to do the followings.
> Check whether /sys/modules/libata/parameters/spindown_compat exists. If it
> does, write 0 to it. For each libata harddisk
> Check whether /sys/class/scsi_disk/h:c:i:l/manage_start_stop exists. If it
> doesn't, synchronize cache and spin the disk down as before. If it does, do
> nothing and continue to the next disk. The file is also accessible as
> /sys/block/sdX/device/scsi_disk:*/manage_start_stop.

You're saying all this is to work around kernels _before_ 2.6.22, and instead 
of updating your shutdown you could just either update the kernel instead?

> If exists some, at this point, exotic shutdown(8) implementation that
> is trying to issue STANDBYBOW on libata/scsi devices, it will get a
> fat warning. The warning could also state that the only supported way
> is to leave complete responsibility of spinning down the hard disks to
> kernel, so eventually it could be cleaned of checks and compatibility
> options.

I'm all for leaving this to the kernel.  I play in the embedded space a lot, 
so the less I can get away with doing, the better. :)

Rob
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