[PATCH] drm/i915/gtt: Defer the free for alloc error paths

* [PATCH] drm/i915/gtt: Defer the free for alloc error paths
@ 2019-07-03 12:32 Chris Wilson
  2019-07-03 12:36 ` Chris Wilson
                   ` (2 more replies)
  0 siblings, 3 replies; 5+ messages in thread
From: Chris Wilson @ 2019-07-03 12:32 UTC (permalink / raw)
  To: intel-gfx; +Cc: Mika Kuoppala, Matthew Auld

If we hit an error while allocating the page tables, we have to unwind
the incomplete updates, and wish to free the unused pd. However, we are
not allowed to be hoding the spinlock at that point, and so must use the
later free to defer it until after we drop the lock.

Fixes: 1d1b5490b91c ("drm/i915/gtt: Replace struct_mutex serialisation for allocation")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_gtt.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index 9e76347e039e..1065753e86fb 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -1489,7 +1489,8 @@ static int gen8_ppgtt_alloc_pdp(struct i915_address_space *vm,
 		gen8_ppgtt_set_pdpe(pdp, vm->scratch_pd, pdpe);
 		GEM_BUG_ON(!atomic_read(&pdp->used));
 		atomic_dec(&pdp->used);
-		free_pd(vm, pd);
+		GEM_BUG_ON(alloc);
+		alloc = pd; /* defer the free to after the lock */
 	}
 	spin_unlock(&pdp->lock);
 unwind:
@@ -1558,7 +1559,8 @@ static int gen8_ppgtt_alloc_4lvl(struct i915_address_space *vm,
 	spin_lock(&pml4->lock);
 	if (atomic_dec_and_test(&pdp->used)) {
 		gen8_ppgtt_set_pml4e(pml4, vm->scratch_pdp, pml4e);
-		free_pd(vm, pdp);
+		GEM_BUG_ON(alloc);
+		alloc = pdp; /* defer the free until after the lock */
 	}
 	spin_unlock(&pml4->lock);
 unwind:
-- 
2.20.1

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

^ permalink raw reply related	[flat|nested] 5+ messages in thread