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Date: Tue, 11 May 2010 22:23:47 +0400
From: Anton Vorontsov <cbouatmailru@gmail.com>
To: Daniel Mack <daniel@caiaq.de>
Cc: linux-kernel@vger.kernel.org, David Woodhouse <dwmw2@infradead.org>,
       Alexey Starikovskiy <astarikovskiy@suse.de>,
       Len Brown <len.brown@intel.com>,
       Mark Brown <broonie@opensource.wolfsonmicro.com>,
       Matt Reimer <mreimer@vpop.net>, Evgeniy Polyakov <zbr@ioremap.net>,
       Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 1/3] pda_power: add support for writeable properties
Message-ID: <20100511182347.GA31831@oksana.dev.rtsoft.ru>
References: <1273595926-26249-1-git-send-email-daniel@caiaq.de>
 <20100511174708.GA26777@oksana.dev.rtsoft.ru>
 <20100511175812.GH30801@buzzloop.caiaq.de>
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On Tue, May 11, 2010 at 07:58:12PM +0200, Daniel Mack wrote:
[...]
> Hmm, no. The code defaults to (S_IRUSR | S_IRGRP | S_IROTH) which is
> 0444, just like it was before. So there shouldn't be any regression. The
> mode is only changed if the psy defines a property_is_writeable()
> callback which returns 1. Or do I miss your point?

Yes, power_supply_attrs is a global array, and you shouldn't change
it between power_supply_register() calls.

If you don't see why it's a bad idea in general, think about it
other way, a race:

...someone registers psy0 with attr X marked as read-only...
...code flow stops before device_create_file(psy0, global->mode)..
[preempt]
...someone registers psy1 with attr X marked as writable...
...you set up global->mode to 0644...
[preempt again]
...we end up calling device_create_file(psy0, 0644)...

-- 
Anton Vorontsov
email: cbouatmailru@gmail.com
irc://irc.freenode.net/bd2