In the next patch, we will make the execlists reset prepare callback
take into account preemption by flushing the context-switch handler.
This is not applicable to the GuC submission backend, so split the two
into their own backend callbacks.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Michał Winiarski <michal.winiarski@xxxxxxxxx>
CC: Michel Thierry <michel.thierry@xxxxxxxxx>
Cc: Jeff McGee <jeff.mcgee@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_guc_submission.c | 39 +++++++++++++++++++++++++++++
drivers/gpu/drm/i915/intel_lrc.c | 11 +-------
2 files changed, 40 insertions(+), 10 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_guc_submission.c b/drivers/gpu/drm/i915/intel_guc_submission.c
index 207cda062626..779c8d3156e5 100644
--- a/drivers/gpu/drm/i915/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/intel_guc_submission.c
@@ -776,6 +776,44 @@ static void guc_submission_tasklet(unsigned long data)
guc_dequeue(engine);
}
+static struct i915_request *
+guc_reset_prepare(struct intel_engine_cs *engine)
+{
+ struct intel_engine_execlists * const execlists = &engine->execlists;
+
+ /*
+ * Prevent request submission to the hardware until we have
+ * completed the reset in i915_gem_reset_finish(). If a request
+ * is completed by one engine, it may then queue a request
+ * to a second via its execlists->tasklet *just* as we are
+ * calling engine->init_hw() and also writing the ELSP.
+ * Turning off the execlists->tasklet until the reset is over
+ * prevents the race.
+ *
+ * Note that this needs to be a single atomic operation on the
+ * tasklet (flush existing tasks, prevent new tasks) to prevent
+ * a race between reset and set-wedged. It is not, so we do the best
+ * we can atm and make sure we don't lock the machine up in the more
+ * common case of recursively being called from set-wedged from inside
+ * i915_reset.
+ */
+ if (!atomic_read(&execlists->tasklet.count))
+ tasklet_kill(&execlists->tasklet);
+ tasklet_disable(&execlists->tasklet);
+
+ /*
+ * We're using worker to queue preemption requests from the tasklet in
+ * GuC submission mode.
+ * Even though tasklet was disabled, we may still have a worker queued.
+ * Let's make sure that all workers scheduled before disabling the
+ * tasklet are completed before continuing with the reset.
+ */
+ if (engine->i915->guc.preempt_wq)
+ flush_workqueue(engine->i915->guc.preempt_wq);
+
+ return i915_gem_find_active_request(engine);
+}
+
/*
* Everything below here is concerned with setup & teardown, and is
* therefore not part of the somewhat time-critical batch-submission
@@ -1235,6 +1273,7 @@ int intel_guc_submission_enable(struct intel_guc *guc)
&engine->execlists;
execlists->tasklet.func = guc_submission_tasklet;
+ engine->reset.prepare = guc_reset_prepare;
engine->park = guc_submission_park;
engine->unpark = guc_submission_unpark;
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index f662a9524233..e5a3ffbc273a 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1688,16 +1688,6 @@ execlists_reset_prepare(struct intel_engine_cs *engine)
tasklet_kill(&execlists->tasklet);
tasklet_disable(&execlists->tasklet);
- /*
- * We're using worker to queue preemption requests from the tasklet in
- * GuC submission mode.
- * Even though tasklet was disabled, we may still have a worker queued.
- * Let's make sure that all workers scheduled before disabling the
- * tasklet are completed before continuing with the reset.
- */
- if (engine->i915->guc.preempt_wq)
- flush_workqueue(engine->i915->guc.preempt_wq);
-
return i915_gem_find_active_request(engine);
}
@@ -2115,6 +2105,7 @@ static void execlists_set_default_submission(struct intel_engine_cs *engine)
engine->cancel_requests = execlists_cancel_requests;
engine->schedule = execlists_schedule;
engine->execlists.tasklet.func = execlists_submission_tasklet;
+ engine->reset.prepare = execlists_reset_prepare;
engine->park = NULL;
engine->unpark = NULL;
--
2.16.2
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