Re: [PATCH] drm/i915: don't update the dri1 breadcrumb with modesetting

[Eugene Shatokhin <eugene.shatokhin@rosalab.ru>]

On 12/11/2013 03:06 PM, Daniel Vetter wrote:
> On Tue, Dec 10, 2013 at 02:48:23PM +0100, Daniel Vetter wrote:
>> On Tue, Dec 10, 2013 at 12:44:12PM +0000, Chris Wilson wrote:
>>> On Tue, Dec 10, 2013 at 01:24:01PM +0100, Daniel Vetter wrote:
>>>> The update is horribly racy since it doesn't protect at all against
>>>> concurrent closing of the master fd. And it can't really since that
>>>> requires us to grab a mutex.
>>>>
>>>> Instead of jumping through hoops and offloading this to a worker
>>>> thread just block this bit of code for the modesetting driver.
>>>>
>>>> Reported-by: Eugene Shatokhin <eugene.shatokhin@rosalab.ru>
>>>> Cc: Eugene Shatokhin <eugene.shatokhin@rosalab.ru>
>>>> Cc: stable@vger.kernel.org
>>>> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
>>>
>>> We should also not be calling update_dri1_breadcrumb unless we have a
>>> USER_INTERRUPT. The other updates to the breadcrumb hws index do not
>>> appear to be serialised by anything other than polling.
>>
>> Well, this is what's been there before and I don't really want to touch
>> dri1/ums code at all. So I think we'll just keep this here until we'll all
>> put it on the big pyre ;-)
>
> Chris and I discusssed the commit message a bit on irc and now the hack
> also spurts a code comment. Merged to -fixes for now, but I'd still like
> to get a tested by from Eugene before sending off the pull request.
> -Daniel
>

Built 3.10.23 with the fix, tested today. The problem has not shown up 
so far.

Tested-by: Eugene Shatokhin <eugene.shatokhin@rosalab.ru>

-- 
Eugene Shatokhin, ROSA Laboratory.
www.rosalab.com