linux-kernel - Re: [PATCH] [PATCH] drm/i915: Fix race condition in accessing GMBUS

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Message-ID: <20120213090440.GA11414@seagal.ffwll.local>
Date:	Mon, 13 Feb 2012 10:04:41 +0100
From:	Ben Widawsky <ben@...dawsk.net>
To:	Yufeng Shen <miletus@...omium.org>
Cc:	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	Eugeni Dodonov <eugeni.dodonov@...el.com>
Subject: Re: [PATCH] [PATCH] drm/i915: Fix race condition in accessing GMBUS

On Fri, Feb 10, 2012 at 12:50:01PM -0500, Yufeng Shen wrote:
> GMBUS has several ports and each has it's own corresponding
> I2C adpater. When multiple I2C adapters call gmbus_xfer() at
> the same time there is a race condition in using the underlying
> GMBUS controller. Fixing this by adding a mutex lock when calling
> gmbus_xfer().
> 
> Signed-off-by: Yufeng Shen <miletus@...omium.org>

I do not see the race. All the i2c transfers should be protected
correctly by the i2c core, or else I think we haven't registered our
device properly. Could you give an example of when/how this can happen?

Ben
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