drm/i915: Refine i915_reset.lock_map

We already use a mutex to serialise i915_reset() and wedging, so all we
need it to link that into i915_request_wait() and we have our lock cycle
detection.

v2.5: Take error mutex for selftests

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190614071023.17929-3-chris@chris-wilson.co.uk

1 files changed, 10 insertions, 2 deletions

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 5ee1ef92a9d9..da76e4d1c7f1 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1444,7 +1444,15 @@ long i915_request_wait(struct i915_request *rq,
 		return -ETIME;
 
 	trace_i915_request_wait_begin(rq, flags);
-	lock_map_acquire(&rq->i915->gt.reset_lockmap);
+
+	/*
+	 * We must never wait on the GPU while holding a lock as we
+	 * may need to perform a GPU reset. So while we don't need to
+	 * serialise wait/reset with an explicit lock, we do want
+	 * lockdep to detect potential dependency cycles.
+	 */
+	mutex_acquire(&rq->i915->gpu_error.wedge_mutex.dep_map,
+		      0, 0, _THIS_IP_);
 
 	/*
 	 * Optimistic spin before touching IRQs.
@@ -1520,7 +1528,7 @@ long i915_request_wait(struct i915_request *rq,
 	dma_fence_remove_callback(&rq->fence, &wait.cb);
 
 out:
-	lock_map_release(&rq->i915->gt.reset_lockmap);
+	mutex_release(&rq->i915->gpu_error.wedge_mutex.dep_map, 0, _THIS_IP_);
 	trace_i915_request_wait_end(rq);
 	return timeout;
 }