Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> Annoyingly, struct_mutex was not entirely eliminated from the reset
> pathway; for reasons of its own, intel_display_resumes() requires
> struct_mutex to prepare the planes it already captured. To avoid the
> immediate problem of a deadlock between the struct_mutex and the reset
> srcu, we have to acquire the reset_lock before struct_mutex in
> i915_gem_fault(). Now any wait underneath struct_mutex will result us in
> having to forcibly reset all inflight rendering, less than ideal.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/i915_gem.c | 20 ++++++++++----------
> 1 file changed, 10 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index cc88e7974422..62e4df1cbf87 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -1834,9 +1834,15 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
>
> wakeref = intel_runtime_pm_get(dev_priv);
>
> + srcu = i915_reset_trylock(dev_priv);
> + if (srcu < 0) {
> + ret = srcu;
> + goto err_rpm;
> + }
> +
> ret = i915_mutex_lock_interruptible(dev);
> if (ret)
> - goto err_rpm;
> + goto err_reset;
>
> /* Access to snoopable pages through the GTT is incoherent. */
> if (obj->cache_level != I915_CACHE_NONE && !HAS_LLC(dev_priv)) {
> @@ -1885,12 +1891,6 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
> if (ret)
> goto err_unpin;
>
> - srcu = i915_reset_trylock(dev_priv);
> - if (srcu < 0) {
> - ret = srcu;
> - goto err_fence;
> - }
> -
> /* Finally, remap it using the new GTT offset */
> ret = remap_io_mapping(area,
> area->vm_start + (vma->ggtt_view.partial.offset << PAGE_SHIFT),
> @@ -1898,7 +1898,7 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
> min_t(u64, vma->size, area->vm_end - area->vm_start),
> &ggtt->iomap);
> if (ret)
> - goto err_reset;
> + goto err_fence;
>
> /* Mark as being mmapped into userspace for later revocation */
> assert_rpm_wakelock_held(dev_priv);
> @@ -1908,14 +1908,14 @@ vm_fault_t i915_gem_fault(struct vm_fault *vmf)
>
> i915_vma_set_ggtt_write(vma);
>
> -err_reset:
> - i915_reset_unlock(dev_priv, srcu);
> err_fence:
> i915_vma_unpin_fence(vma);
> err_unpin:
> __i915_vma_unpin(vma);
> err_unlock:
> mutex_unlock(&dev->struct_mutex);
> +err_reset:
> + i915_reset_unlock(dev_priv, srcu);
> err_rpm:
> intel_runtime_pm_put(dev_priv, wakeref);
> i915_gem_object_unpin_pages(obj);
> --
> 2.20.1
>
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