On 4/2/19 10:41 AM, Kazlauskas, Nicholas wrote:
> On 4/2/19 10:28 AM, Christian König wrote:
>> Don't block others while waiting for the fences to finish, concurrent
>> submission is perfectly valid in this case and holding the lock can
>> prevent killed applications from terminating.
>>
>> Signed-off-by: Christian König <christian.koenig@xxxxxxx>
>
> Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@xxxxxxx>
>
> I do recall having the discussion about this a while back with you and
> Andrey.
>
> I highly doubt that the flags would ever really change here (if they're
> even capable) between the wait and the lock so I think this is fine.
>
> I think there's a bigger problem with that and how they could
> potentially change between atomic check and atomic commit tail anyway
> (and doing something bad after we think it's passed validation).
>
> But this is mostly a theoretical concern I think rather than a practical
> one.
>
> Thanks.
>
> Nicholas Kazlauskas
...and waiting for the fence isn't really analogous to ensuring that
they can't change in the first place I suppose.
This looks fine.
Nicholas Kazlauskas
>
>
>> ---
>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 13 ++++++++-----
>> 1 file changed, 8 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> index 697af51d403a..9426e701a7b6 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -5129,23 +5129,26 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
>> continue;
>> }
>>
>> + abo = gem_to_amdgpu_bo(fb->obj[0]);
>> +
>> + /* Wait for all fences on this FB */
>> + r = reservation_object_wait_timeout_rcu(abo->tbo.resv, true,
>> + false,
>> + MAX_SCHEDULE_TIMEOUT);
>> + WARN_ON(r < 0);
>> +
>> /*
>> * TODO This might fail and hence better not used, wait
>> * explicitly on fences instead
>> * and in general should be called for
>> * blocking commit to as per framework helpers
>> */
>> - abo = gem_to_amdgpu_bo(fb->obj[0]);
>> r = amdgpu_bo_reserve(abo, true);
>> if (unlikely(r != 0)) {
>> DRM_ERROR("failed to reserve buffer before flip\n");
>> WARN_ON(1);
>> }
>>
>> - /* Wait for all fences on this FB */
>> - WARN_ON(reservation_object_wait_timeout_rcu(abo->tbo.resv, true, false,
>> - MAX_SCHEDULE_TIMEOUT) < 0);
>> -
>> amdgpu_bo_get_tiling_flags(abo, &tiling_flags);
>>
>> amdgpu_bo_unreserve(abo);
>>
>
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