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Message-ID: <d120d500050321064028e255fe@mail.gmail.com>
Date: Mon, 21 Mar 2005 09:40:04 -0500
From: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Reply-To: dtor_core@ameritech.net
To: Tejun Heo <htejun@gmail.com>
Subject: Re: [PATCH] driver model/scsi: synchronize pm calls with probe/remove
Cc: mochel@digitalimplant.org, James.Bottomley@steeleye.com,
       linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
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On Mon, 21 Mar 2005 18:18:46 +0900, Tejun Heo <htejun@gmail.com> wrote:
> Hello, Dmitry, Mochel and James.
> 
> I've been looking at sd code and found seemingly bogus 'if (!sdkp)'
> tests with /* this can happen */ comment.  I've digged changelog and
> found out that this was to prevent oops which occurs if some driver
> gets stuck inside ->probe and the machine goes down and calls back
> ->remove.  IMHO, we should avoid this problem by fixing driver ->probe
> or ->remove callbacks instead of detecting and bypassing
> half-initialized/destroyed devices in pm callbacks.
> 
> This patch read-locks a device's bus using device_pm_down_read_bus()
> before invoking any pm callback.

Hi Tejun,

There are talks about getting rid of bus's rwsem and replacing it with
a per-device semaphore to serialize probe, remove, suspend and resume.
This should resolve entire host of problems including this one, if I
unrerstand it correctly.

Please take a look here:
http://seclists.org/lists/linux-kernel/2005/Mar/5847.html

-- 
Dmitry