[PATCH 8/9] drm/i915: Combine set-wedged protection and tasklet kicking

[Chris Wilson]

Around request submission, we protect the call to schedule with a
premption disable loop to prevent set-wedge chaning function pointers
underneath us. This also prevents the tasklet running on the local CPU,
a trick we use immediately afterwards to forcibly execute the tasklet
after submission. We can combine the two wlog, and ensure that the
tasklet is only executed (on the local CPU) after we complete our
updates to the submission queue (and not after an intermediate,
incomplete update).

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/i915_request.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
index e4cf76ec14a6..88ee444679d4 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1110,12 +1110,9 @@ void __i915_request_add(struct i915_request *request, bool flush_caches)
 	 * decide whether to preempt the entire chain so that it is ready to
 	 * run at the earliest possible convenience.
 	 */
-	rcu_read_lock();
+	local_bh_disable();
 	if (engine->schedule)
 		engine->schedule(request, &request->ctx->sched);
-	rcu_read_unlock();
-
-	local_bh_disable();
 	i915_sw_fence_commit(&request->submit);
 	local_bh_enable(); /* Kick the execlists tasklet if just scheduled */
 
-- 
2.17.0