On 06/03/2020 13:38, Chris Wilson wrote:
Skip useless priority bumping on adding a new dependency, but otherwise
prevent tasklet scheduling until we have completed all the potential
rescheduling.

Signed-off-by: Chris Wilson <[email protected]>
---
  drivers/gpu/drm/i915/i915_scheduler.c | 7 ++++++-
  1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_scheduler.c 
b/drivers/gpu/drm/i915/i915_scheduler.c
index 52f71e83e088..603cba36d6a4 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -209,6 +209,8 @@ static void kick_submission(struct intel_engine_cs *engine,
        if (!inflight)
                goto unlock;
+ engine->execlists.queue_priority_hint = prio;
+

What is the significance of moving this up? I couldn't correlate it to the commit message.

        /*
         * If we are already the currently executing context, don't
         * bother evaluating if we should preempt ourselves.
@@ -216,7 +218,6 @@ static void kick_submission(struct intel_engine_cs *engine,
        if (inflight->context == rq->context)
                goto unlock;
- engine->execlists.queue_priority_hint = prio;
        if (need_preempt(prio, rq_prio(inflight)))
                tasklet_hi_schedule(&engine->execlists.tasklet);
@@ -463,11 +464,15 @@ int i915_sched_node_add_dependency(struct i915_sched_node *node,
        if (!dep)
                return -ENOMEM;
+ local_bh_disable();
+
        if (!__i915_sched_node_add_dependency(node, signal, dep,
                                              I915_DEPENDENCY_EXTERNAL |
                                              I915_DEPENDENCY_ALLOC))
                i915_dependency_free(dep);
+ local_bh_enable(); /* kick submission tasklet */
+

And this presumably postpones the tasklet until __bump_priority -> __i915_schedule is finished. But then why the request submission path which calls __i915_sched_node_add_dependency directly does not need this treatment?

Regards,

Tvrtko

        return 0;
  }
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