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

Message ID 1435881253-4912-1-git-send-email-greg@chown.ath.cx
State New
Headers show

Commit Message

Grigori Goronzy July 2, 2015, 11:54 p.m. UTC
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@chown.ath.cx>
---
 drivers/gpu/drm/radeon/radeon_gem.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

Comments

Christian König July 3, 2015, 9:45 a.m. UTC | #1
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@chown.ath.cx>

Patche #1-#3 are Reviewed-by: Christian König <christian.koenig@amd.com>

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;
>   }
>
Alex Deucher July 6, 2015, 9:14 p.m. UTC | #2
On Fri, Jul 3, 2015 at 5:45 AM, Christian König <deathsimple@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@chown.ath.cx>
>
>
> Patche #1-#3 are Reviewed-by: Christian König <christian.koenig@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;
>>   }
>>
>
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

Patch
diff mbox

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;
 }