drm/i915/execlists: Keep virtual context alive until after we kick

The call to kick_siblings() dereferences the rq->context, so we should
not drop our local reference until afterwards!

v2: Stick to setting ce.inflight=NULL before kicking as this is what the
other threads will check to see if the context is ready for takeover.

Fixes: 22b7a426bbe1 ("drm/i915/execlists: Preempt-to-busy")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190621080729.2652-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index f8ad490..faa9a2e 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -557,9 +557,6 @@ execlists_schedule_out(struct i915_request *rq)
                intel_engine_context_out(ce->inflight);
                execlists_context_status_change(rq, INTEL_CONTEXT_SCHEDULE_OUT);
 
-               ce->inflight = NULL;
-               intel_context_put(ce);
-
                /*
                 * If this is part of a virtual engine, its next request may
                 * have been blocked waiting for access to the active context.
@@ -569,8 +566,11 @@ execlists_schedule_out(struct i915_request *rq)
                 * request before the tasklet runs and do not need to rebuild
                 * each virtual tree and kick everyone again.
                 */
+               ce->inflight = NULL;
                if (rq->engine != ce->engine)
                        kick_siblings(rq, ce);
+
+               intel_context_put(ce);
        }
 
        i915_request_put(rq);