Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> A call to wait for the GT to idle from inside the put_pages fallback is
> prone to cause an uninterruptible livelock. As it does not provide
> adequate serialisation with new requests, simply fallback to a trial
s/trial/trivial
> sleep.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem_gtt.c | 25 ++++++++++---------------
> 1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
> index c5ee1567f3d1..d2350a4c6606 100644
> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
> @@ -55,22 +55,17 @@ int i915_gem_gtt_prepare_pages(struct drm_i915_gem_object *obj,
> void i915_gem_gtt_finish_pages(struct drm_i915_gem_object *obj,
> struct sg_table *pages)
> {
> - struct drm_i915_private *dev_priv = to_i915(obj->base.dev);
> - struct device *kdev = &dev_priv->drm.pdev->dev;
> - struct i915_ggtt *ggtt = &dev_priv->ggtt;
> -
> - if (unlikely(ggtt->do_idle_maps)) {
> - /* XXX This does not prevent more requests being submitted! */
> - if (intel_gt_retire_requests_timeout(ggtt->vm.gt,
> - -MAX_SCHEDULE_TIMEOUT)) {
> - drm_err(&dev_priv->drm,
> - "Failed to wait for idle; VT'd may hang.\n");
> - /* Wait a bit, in hopes it avoids the hang */
> - udelay(10);
> - }
> - }
> + struct drm_i915_private *i915 = to_i915(obj->base.dev);
> + struct i915_ggtt *ggtt = &i915->ggtt;
> +
> + /* XXX This does not prevent more requests being submitted! */
> + if (unlikely(ggtt->do_idle_maps))
> + /* Wait a bit, in hope it avoids the hang */
> + usleep_range(100, 250);
>
> - dma_unmap_sg(kdev, pages->sgl, pages->nents, PCI_DMA_BIDIRECTIONAL);
> + dma_unmap_sg(&i915->drm.pdev->dev,
> + pages->sgl, pages->nents,
> + PCI_DMA_BIDIRECTIONAL);
> }
>
> /**
> --
> 2.20.1
>
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