[Intel-gfx] [PATCH] drm/i915: Wait on vma activity before taking the mutex

[Chris Wilson <chris@chris-wilson.co.uk>]

Optimistically wait for the prior vma activity before taking the mutex
to minimise the mutex hold time while unbinding. We will then verify the
vma is idle with a second wait under the mutex to ensure it is safe to
unbind.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_vma.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index 08b91e88c229..9a79b26b925e 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -1268,16 +1268,21 @@ int i915_vma_unbind(struct i915_vma *vma)
 		/* XXX not always required: nop_clear_range */
 		wakeref = intel_runtime_pm_get(&vm->i915->runtime_pm);
 
+	/* Optimistic wait before taking the mutex */
+	err = i915_vma_sync(vma);
+	if (err)
+		goto out_rpm;
+
 	err = mutex_lock_interruptible(&vm->mutex);
 	if (err)
-		return err;
+		goto out_rpm;
 
 	err = __i915_vma_unbind(vma);
 	mutex_unlock(&vm->mutex);
 
+out_rpm:
 	if (wakeref)
 		intel_runtime_pm_put(&vm->i915->runtime_pm, wakeref);
-
 	return err;
 }
 
-- 
2.25.0

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