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Commit 43a8f684 authored by Chris Wilson's avatar Chris Wilson
Browse files

drm/i915: Reorder struct_mutex-vs-reset_lock in i915_gem_fault() 



Annoyingly, struct_mutex was not entirely eliminated from the reset
pathway; for reasons of its own, intel_display_resume() 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, but
better than a deadlock (and will do for the short term).

Signed-off-by: default avatarChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: default avatarMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190221102924.13442-1-chris@chris-wilson.co.uk
parent 2a3902bd

drivers/gpu/drm/i915/i915_gem.c

+10 −10
Original line number Diff line number Diff line
@@ -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);