Commit 0725d9a3 authored Nov 18, 2019 by Chris Wilson Committed by Joonas Lahtinen Nov 26, 2019

drm/i915/gt: Make intel_ring_unpin() safe for concurrent pint



In order to avoid some nasty mutex inversions, commit 09c5ab38
("drm/i915: Keep rings pinned while the context is active") allowed the
intel_ring unpinning to be run concurrently with the next context
pinning it. Thus each step in intel_ring_unpin() needed to be atomic and
ordered in a nice onion with intel_ring_pin() so that the lifetimes
overlapped and were always safe.

Sadly, a few steps in intel_ring_unpin() were overlooked, such as
closing the read/write pointers of the ring and discarding the
intel_ring.vaddr, as these steps were not serialised with
intel_ring_pin() and so could leave the ring in disarray.

Fixes: 09c5ab38 ("drm/i915: Keep rings pinned while the context is active")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191118230254.2615942-6-chris@chris-wilson.co.uk


(cherry picked from commit a266bf42)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

parent 31177017

drivers/gpu/drm/i915/gt/intel_ring.c

+4 −9

Original line number	Diff line number	Diff line
		@@ -57,9 +57,10 @@ int intel_ring_pin(struct intel_ring *ring)

		i915_vma_make_unshrinkable(vma);

		GEM_BUG_ON(ring->vaddr);
		ring->vaddr = addr;
		/* Discard any unused bytes beyond that submitted to hw. */
		intel_ring_reset(ring, ring->emit);

		ring->vaddr = addr;
		return 0;

		err_ring:
		@@ -85,20 +86,14 @@ void intel_ring_unpin(struct intel_ring *ring)
		if (!atomic_dec_and_test(&ring->pin_count))
		return;

		/* Discard any unused bytes beyond that submitted to hw. */
		intel_ring_reset(ring, ring->emit);

		i915_vma_unset_ggtt_write(vma);
		if (i915_vma_is_map_and_fenceable(vma))
		i915_vma_unpin_iomap(vma);
		else
		i915_gem_object_unpin_map(vma->obj);

		GEM_BUG_ON(!ring->vaddr);
		ring->vaddr = NULL;

		i915_vma_unpin(vma);
		i915_vma_make_purgeable(vma);
		i915_vma_unpin(vma);
		}

		static struct i915_vma create_ring_vma(struct i915_ggtt ggtt, int size)

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