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

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Date:	Wed, 08 Aug 2007 13:04:50 -0400
From:	Mark Lord <liml@....ca>
To:	Tejun Heo <htejun@...il.com>
Cc:	Michael Sedkowski <sedmich@...il.com>, 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

Tejun Heo wrote:
> Mark Lord wrote:
>> Further to this, if I have an active-writer running at the time of suspend,
>> then even my scripted "sleep 1" is not good enough, as additional writes
>> are still happening before/after the flush.
>>
>> Now I'll reboot and try it with the "sleep 1" hardcoded inside
>> sd_suspend().
> 
> Hmmm... queue quiescing might be broken.  Can you verify there's no
> command issued between STANDBYNOW1 and suspending?

Yeah, I verified that already.  Nothing happens other than
the FLUSH_CACHE_EXT and STANDBY commands.

I've now tried adding various sleeps into the sd_suspend() routine.
The sleeps actually do sleep, but they don't seem to solve the problem there.
The "hdparm -F /dev/sda ; sleep 1" inside my script actually works better,
though even it fails if there's a ton of writes happening.

I put a 4-second sleep in front of the sd_start_stop_device() call,
and here is what I observed:

the disk light flickers briefly,
then the system does absolutely nothing for the 4-seconds,
and then it flickers again,
and then the light comes on solid for a second or two,
and then it suspends.

I am ssssoooooooo confused now.  :)

We need Eric (from Seagate) to enlighten us.

Cheers

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