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SubjectRe: [PATCH 3/3] drm/amdgpu: Switch to interrupted wait to recover from ring hang.
"Panariti, David" <David.Panariti@amd.com> writes:

> Andrey Grodzovsky <andrey.grodzovsky@amd.com> writes:
>> Kind of dma_fence_wait_killable, except that we don't have such API
>> (maybe worth adding ?)
> Depends on how many places it would be called, or think it might be called. Can always factor on the 2nd time it's needed.
> Factoring, IMO, rarely hurts. The factored function can easily be visited using `M-.' ;->
>
> Also, if the wait could be very long, would a log message, something like "xxx has run for Y seconds." help?
> I personally hate hanging w/no info.

Ugh. This loop appears susceptible to loosing wake ups. There are
races between when a wake-up happens, when we clear the sleeping state,
and when we test the stat to see if we should stat awake. So yes
implementing a dma_fence_wait_killable that handles of all that
correctly sounds like an very good idea.

Eric


>> If the ring is hanging for some reason allow to recover the waiting by sending fatal signal.
>>
>> Originally-by: David Panariti <David.Panariti@amd.com>
>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
>> ---
>> drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 14 ++++++++++----
>> 1 file changed, 10 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>> index eb80edf..37a36af 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
>> @@ -421,10 +421,16 @@ int amdgpu_ctx_wait_prev_fence(struct amdgpu_ctx *ctx, unsigned ring_id)
>>
>> if (other) {
>> signed long r;
>> - r = dma_fence_wait_timeout(other, false, MAX_SCHEDULE_TIMEOUT);
>> - if (r < 0) {
>> - DRM_ERROR("Error (%ld) waiting for fence!\n", r);
>> - return r;
>> +
>> + while (true) {
>> + if ((r = dma_fence_wait_timeout(other, true,
>> + MAX_SCHEDULE_TIMEOUT)) >= 0)
>> + return 0;
>> +
>> + if (fatal_signal_pending(current)) {
>> + DRM_ERROR("Error (%ld) waiting for fence!\n", r);
>> + return r;
>> + }
>> }
>> }
>>
>> --
>> 2.7.4
>>
Eric

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