On 2/14/19 4:05 AM, Christian König wrote:
> Am 13.02.19 um 19:58 schrieb Andrey Grodzovsky:
>> When ring hang happens amdgpu_dm_commit_planes during flip is holding
>> the BO reserved and then stack waiting for fences to signal in
>> reservation_object_wait_timeout_rcu (which won't signal because there
>> was a hnag). Then when we try to shutdown display block during reset
>> recovery from drm_atomic_helper_suspend we also try to reserve the BO
>> from dm_plane_helper_cleanup_fb ending in deadlock.
>> Also remove useless WARN_ON
>
> Well it is good that you pointed this out, but there are more problems
> than just waiting wile the BO is reserved here.
>
>>
>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
>> ---
>> drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 19
>> +++++++++++++------
>> 1 file changed, 13 insertions(+), 6 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 acc4ff8..f8dec36 100644
>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
>> @@ -4802,14 +4802,21 @@ static void amdgpu_dm_commit_planes(struct
>> drm_atomic_state *state,
>> */
>> abo = gem_to_amdgpu_bo(fb->obj[0]);
>> r = amdgpu_bo_reserve(abo, true);
>
> Well why do we reserve the BO in the first place? As the name
> indicates reservation_object_wait_timeout_rcu() just uses rcu to wait
> for the BO to be idle, no need to actually reserve it at all.
That a good point, I honestly can't remember any more why it's here...
It does look unnecessary given that we are not validating the BO here.
>
>> - if (unlikely(r != 0)) {
>> + 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);
>> + /*
>> + * Wait for all fences on this FB. Do limited wait to avoid
>> + * deadlock during GPU reset when this fence will not
>> signal
>> + * but we hold reservation lock for the BO.
>> + */
>> + r = reservation_object_wait_timeout_rcu(abo->tbo.resv,
>> + true, false,
>
> Does this waiting happen in a work item or process context? If it's
> process context we should actually try to wait interruptible here.
Work item only.
Andrey
>
> Regards,
> Christian.
>
>> + msecs_to_jiffies(5000));
>> + if (unlikely(r == 0))
>> + DRM_ERROR("Waiting for fences timed out.");
>> +
>> +
>> amdgpu_bo_get_tiling_flags(abo, &tiling_flags);
>
_______________________________________________
amd-gfx mailing list
amd-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/amd-gfx
