Chris Wilson <[email protected]> writes:

> As we have pinned the timeline (using tl->active_count), we can safely
> drop the tl->mutex as we wait for what we believe to be the final
> request on that timeline. This is useful for ensuring that we do not
> block the engine heartbeat by hogging the kernel_context's timeline on a
> dead GPU.
>
> References: https://gitlab.freedesktop.org/drm/intel/issues/1364
> Fixes: 058179e72e09 ("drm/i915/gt: Replace hangcheck by heartbeats")
> Fixes: f33a8a51602c ("drm/i915: Merge wait_for_timelines with retire_request")
> Signed-off-by: Chris Wilson <[email protected]>
> Cc: Mika Kuoppala <[email protected]>
> ---
>  drivers/gpu/drm/i915/gt/intel_gt_requests.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_gt_requests.c 
> b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> index 8a5054f21bf8..24c99d0838af 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> +++ b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
> @@ -147,24 +147,32 @@ long intel_gt_retire_requests_timeout(struct intel_gt 
> *gt, long timeout)
>  
>                       fence = i915_active_fence_get(&tl->last_request);
>                       if (fence) {
> +                             mutex_unlock(&tl->mutex);
> +
>                               timeout = dma_fence_wait_timeout(fence,
>                                                                interruptible,
>                                                                timeout);
>                               dma_fence_put(fence);
> +
> +                             /* Retirement is best effort */
> +                             if (!mutex_trylock(&tl->mutex)) {
> +                                     active_count++;
> +                                     goto out_active;
> +                             }
>                       }
>               }
>  
>               if (!retire_requests(tl) || flush_submission(gt))
>                       active_count++;
> +             mutex_unlock(&tl->mutex);
>  
> -             spin_lock(&timelines->lock);
> +out_active:  spin_lock(&timelines->lock);
>  
> -             /* Resume iteration after dropping lock */
> +             /* Resume list iteration after reacquiring spinlock */

Now it is in mint.

Reviewed-by: Mika Kuoppala <[email protected]>

>               list_safe_reset_next(tl, tn, link);
>               if (atomic_dec_and_test(&tl->active_count))
>                       list_del(&tl->link);
>  
> -             mutex_unlock(&tl->mutex);
>  
>               /* Defer the final release to after the spinlock */
>               if (refcount_dec_and_test(&tl->kref.refcount)) {
> -- 
> 2.25.1
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