[PATCH 1/4] drm/radeon: use RCU query for GEM_BUSY syscall

[Alex Deucher]

On Fri, Jul 3, 2015 at 5:45 AM, Christian König <deathsimple at vodafone.de> wrote:
> On 03.07.2015 01:54, Grigori Goronzy wrote:
>>
>> We don't need to call the (expensive) radeon_bo_wait, checking the
>> fences via RCU is much faster. The reservation done by radeon_bo_wait
>> does not save us from any race conditions.
>>
>> Signed-off-by: Grigori Goronzy <greg at chown.ath.cx>
>
>
> Patche #1-#3 are Reviewed-by: Christian König <christian.koenig at amd.com>
>

Applied 1-3.  thanks!

Alex

> Patch #4 is a nice catch, but as Michel already noted needs more thoughts
> for a complete fix.
>
> Regards,
> Christian.
>
>
>> ---
>>   drivers/gpu/drm/radeon/radeon_gem.c | 11 ++++++++---
>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/radeon/radeon_gem.c
>> b/drivers/gpu/drm/radeon/radeon_gem.c
>> index ac3c131..7199e19 100644
>> --- a/drivers/gpu/drm/radeon/radeon_gem.c
>> +++ b/drivers/gpu/drm/radeon/radeon_gem.c
>> @@ -428,7 +428,6 @@ int radeon_gem_mmap_ioctl(struct drm_device *dev, void
>> *data,
>>   int radeon_gem_busy_ioctl(struct drm_device *dev, void *data,
>>                           struct drm_file *filp)
>>   {
>> -       struct radeon_device *rdev = dev->dev_private;
>>         struct drm_radeon_gem_busy *args = data;
>>         struct drm_gem_object *gobj;
>>         struct radeon_bo *robj;
>> @@ -440,10 +439,16 @@ int radeon_gem_busy_ioctl(struct drm_device *dev,
>> void *data,
>>                 return -ENOENT;
>>         }
>>         robj = gem_to_radeon_bo(gobj);
>> -       r = radeon_bo_wait(robj, &cur_placement, true);
>> +
>> +       r = reservation_object_test_signaled_rcu(robj->tbo.resv, true);
>> +       if (r == 0)
>> +               r = -EBUSY;
>> +       else
>> +               r = 0;
>> +
>> +       cur_placement = ACCESS_ONCE(robj->tbo.mem.mem_type);
>>         args->domain = radeon_mem_type_to_domain(cur_placement);
>>         drm_gem_object_unreference_unlocked(gobj);
>> -       r = radeon_gem_handle_lockup(rdev, r);
>>         return r;
>>   }
>>
>
>
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