[PATCH] drm/i915: return DRIVER_NAME for the fence driver name

[Matthew Auld]

The first tracepoint for a request is trace_dma_fence_init which is
called in the ctor before we have properly setup the request->engine. So
if it's a non-recycled request the rq->engine might be NULL, or some
garbage value, which leads to a crash.

Since we are not permitted to use kmem_cache_zalloc() here with
SLAB_TYPESAFE_BY_RCU, one approach is simply to return DRIVER_NAME. We
can then revisit this later if we decide to get rid of
SLAB_TYPESAFE_BY_RCU.

Fixes: 855e39e65cfc ("drm/i915: Initialise basic fence before acquiring seqno")
Signed-off-by: Matthew Auld <matthew.auld at intel.com>
Cc: Michael Mason <michael.w.mason at intel.com>
Cc: Daniel Vetter <daniel at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_request.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index 1014c71cf7f5..55fa94bde22e 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -61,7 +61,7 @@ static struct i915_global_request {
 
 static const char *i915_fence_get_driver_name(struct dma_fence *fence)
 {
-	return dev_name(to_request(fence)->engine->i915->drm.dev);
+	return DRIVER_NAME;
 }
 
 static const char *i915_fence_get_timeline_name(struct dma_fence *fence)
-- 
2.26.3