linux-kernel - Re: [PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object lookups v3

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Date:	Tue, 20 Nov 2012 17:59:57 +1000
From:	Dave Airlie <airlied@...il.com>
To:	Thomas Hellstrom <thellstrom@...are.com>
Cc:	airlied@...hat.com, dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] drm/ttm, drm/vmwgfx: Use RCU locking for object
 lookups v3

On Tue, Nov 20, 2012 at 4:44 PM, Thomas Hellstrom <thellstrom@...are.com> wrote:
> On 11/20/2012 07:19 AM, Dave Airlie wrote:
>>
>> On Tue, Nov 6, 2012 at 9:31 PM, Thomas Hellstrom <thellstrom@...are.com>
>> wrote:
>>>
>>> The mostly used lookup+get put+potential_destroy path of TTM objects
>>> is converted to use RCU locks. This will substantially decrease the
>>> amount
>>> of locked bus cycles during normal operation.
>>> Since we use kfree_rcu to free the objects, no rcu synchronization is
>>> needed
>>> at module unload time.
>>
>> As this is the first use of RCU in a drm driver from what I can see,
>> let me remind that the
>> RCU patent agreement AFAIK only covers GPL works.
>>
>> So non-GPL or other OSes porting this code should take not of this.
>>
>> Dave.
>
>
> From VMware's side this won't be a problem, since other VMware kernel
> modules (VMCI IIRC) use RCU.
>
> In any case I have a new version of the "vmwgfx optimization" patch series
> that mostly add documentation and
> annotation (by  using a drm_ht_xxx_rcu) interface for hashtab, after an
> internal review by Dmitry Torkov. I see you've already
> applied the original patch series. Do you want me to send out the new one or
> rebase it against current drm-next?

Can you rebase it on top of -next?

Dave.
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