From mboxrd@z Thu Jan  1 00:00:00 1970
From: Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH 2/3] drm/i915: close PM interrupt masking
 races in the rps work func
Date: Mon, 5 Sep 2011 08:38:07 +0200
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To: Ben Widawsky <ben@bwidawsk.net>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>, intel-gfx@lists.freedesktop.org
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On Sun, Sep 04, 2011 at 09:38:56PM +0000, Ben Widawsky wrote:
> Oops, you're totally right, I think I meant:
> -       I915_WRITE(GEN6_PMIMR, pm_imr & ~pm_iir);
> +       I915_WRITE(GEN6_PMIMR, dev_priv->pm_iir);

Imo still racy without the irqsafe rps_lock around it. gcc is free to
compile that into a separate load and store which the irq handler can get
in between and change dev_priv->pm_iir and PMIMR. The race is now only one
instruction wide, though ;-)
-Daniel
-- 
Daniel Vetter
Mail: daniel@ffwll.ch
Mobile: +41 (0)79 365 57 48