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

In order to avoid some nasty mutex inversions, commit 09c5ab384f
("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: 09c5ab384f ("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 a266bf4200)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
This commit is contained in:
Chris Wilson 2019-11-18 23:02:40 +00:00 committed by Joonas Lahtinen
parent 311770173f
commit 0725d9a318
1 changed files with 4 additions and 9 deletions
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13
drivers/gpu/drm/i915/gt/intel_ring.c
View File

@ -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)