[Intel-gfx] [PATCH 3/4] drm/i915/perf: do not warn when OA buffer is already allocated

[Lionel Landwerlin]

If 2 processes race to open the perf stream, it's possible that one of them
will see that OA buffer has already been allocated, while a previous process
is still finishing to reprogram the hardware (on gen8+).

The opening sequence has been reworked a few times and we probably lost
track of the order in which things are supposed to happen.

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
---
 drivers/gpu/drm/i915/i915_perf.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 88f3f9b6a353..a648ded97969 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -1494,13 +1494,15 @@ static int alloc_oa_buffer(struct drm_i915_private *dev_priv)
 	struct i915_vma *vma;
 	int ret;
 
-	if (WARN_ON(dev_priv->perf.oa.oa_buffer.vma))
-		return -ENODEV;
-
 	ret = i915_mutex_lock_interruptible(&dev_priv->drm);
 	if (ret)
 		return ret;
 
+	if (dev_priv->perf.oa.oa_buffer.vma) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
 	BUILD_BUG_ON_NOT_POWER_OF_2(OA_BUFFER_SIZE);
 	BUILD_BUG_ON(OA_BUFFER_SIZE < SZ_128K || OA_BUFFER_SIZE > SZ_16M);
 
-- 
2.19.1