linux-kernel - Re: [PATCH] drm: Fix lock order reversal between mmap_sem and struct

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Date:	Wed, 18 Feb 2009 16:02:20 +0800
From:	Wang Chen <wangchen@...fujitsu.com>
To:	Eric Anholt <eric@...olt.net>
CC:	linux-kernel@...r.kernel.org, dri-devel@...ts.sourceforge.net
Subject: Re: [PATCH] drm: Fix lock order reversal between mmap_sem and struct_mutex.

Eric Anholt said the following on 2009-2-18 8:59:
> The basic problem was
> mmap_sem (do_mmap()) -> struct_mutex (drm_gem_mmap(), i915_gem_fault())
> struct_mutex (i915_gem_execbuffer()) -> mmap_sem (copy_from/to_user())
> 
> We have plenty of places where we want to hold device state the same
> (struct_mutex) while we move a non-trivial amount of data
> (copy_from/to_user()), such as i915_gem_pwrite().  Solve this by moving the
> easy things that needed struct_mutex with mmap_sem held to using a lock to
> cover just those data structures (offset hash and offset manager), and do
> trylock and reschedule in fault.
> 

Eric, I tested the patch.
But following bug still doesn't disappear.
http://bugzilla.kernel.org/show_bug.cgi?id=12419

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