linux-kernel - Re: [PATCH] firewire: reread config ROM when device reset the bus

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Date:	Mon, 03 Mar 2008 19:35:07 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Greg Kroah-Hartman <gregkh@...e.de>,
	Kristian Høgsberg 
	<krh@...planet.net>
CC:	linux1394-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] firewire: reread config ROM when device reset the bus

I wrote:
>> On Mon, Mar 3, 2008 at 11:51 AM, Stefan Richter
>> <stefanr@...6.in-berlin.de> wrote:
[...rewriting data of a device with children devices whose driver probe 
accesses these data...]
>>>  Maybe I should rather use fw-device.c::idr_rwsem instead of device.sem,
>>>  to have better control over who takes the mutex when.  Could also be a
>>>  new dedicated mutex but we don't want to end up with too many of 
>>>  them...
[...]
> Ah, wait, there is a 3rd reader: sbp2_probe's sbp2_scan_unit_dir.  So, 
> using dev->sem is actually the nicest way for now.

Or not.  The necessary protection for this and other driver->probe()s 
would be the device->parent.sem, not the device->sem itself.  There seem 
to be several ways how a driver probe may be entered (adding a device 
when the driver is already there; attaching a driver when the device is 
already there...) and I am not sure whether all these paths take the 
device->parent.sem around the probe.  It doesn't seem to be always the case.

Greg, can you comment on this?
-- 
Stefan Richter
-=====-==--- --== ---==
http://arcgraph.de/sr/
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