drm/i915: Allow interrupts when taking the timeline->mutex

Before we commit ourselves to writing commands into the
ringbuffer and submitting the request, allow signals to interrupt
acquisition of the timeline mutex. We allow ourselves to be interrupted
at any time later if we need to block for space in the ring, anyway.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190610103610.19883-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/gt/intel_context.h

@@ -113,10 +113,11 @@ static inline void intel_context_put(struct intel_context *ce)
 	kref_put(&ce->ref, ce->ops->destroy);
 }
 
-static inline void intel_context_timeline_lock(struct intel_context *ce)
+static inline int __must_check
+intel_context_timeline_lock(struct intel_context *ce)
 	__acquires(&ce->ring->timeline->mutex)
 {
-	mutex_lock(&ce->ring->timeline->mutex);
+	return mutex_lock_interruptible(&ce->ring->timeline->mutex);
 }
 
 static inline void intel_context_timeline_unlock(struct intel_context *ce)

drivers/gpu/drm/i915/i915_request.c

@@ -784,8 +784,11 @@ struct i915_request *
 i915_request_create(struct intel_context *ce)
 {
 	struct i915_request *rq;
+	int err;
 
-	intel_context_timeline_lock(ce);
+	err = intel_context_timeline_lock(ce);
+	if (err)
+		return ERR_PTR(err);
 
 	/* Move our oldest request to the slab-cache (if not in use!) */
 	rq = list_first_entry(&ce->ring->request_list, typeof(*rq), ring_link);