From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Mon, 7 May 2018 14:57:26 +0100
Subject: drm/i915: Disable tasklet scheduling across initial scheduling
Git-commit: 71ace7ca2545d7cd7522988c16ad6c94e6169366
Patch-mainline: v4.18-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166
During request submission, we call the engine->schedule() function so
that we may reorder the active requests as required for inheriting the
new request's priority. This may schedule several tasklets to run on the
local CPU, but we will need to schedule the tasklets again for the new
request. Delay all the local tasklets until the end, so that we only
have to process the queue just once.
v2: Beware PREEMPT_RCU, as then local_bh_disable() is then not a
superset of rcu_read_lock().
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180507135731.10587-2-chris@chris-wilson.co.uk
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
drivers/gpu/drm/i915/i915_request.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -1110,12 +1110,11 @@ void __i915_request_add(struct i915_requ
* 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();
+ rcu_read_lock(); /* RCU serialisation for set-wedged protection */
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 */