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authorChris Wilson <chris@chris-wilson.co.uk>2019-11-03 16:23:05 +0000
committerRodrigo Vivi <rodrigo.vivi@intel.com>2019-11-18 11:25:16 -0800
commitc0fa92ec8902492a599e6eabff9e3ef43d1afee6 (patch)
tree0deedfd1f4bba1099195309b11024e5451071997
parent2d691aeca4aecbb8d0414a777a46981a8e142b05 (diff)
downloadlinux-stericsson-c0fa92ec8902492a599e6eabff9e3ef43d1afee6.tar.gz
drm/i915: Protect request peeking with RCU
Since the execlists_active() is no longer protected by the engine->active.lock, we need to protect the request pointer with RCU to prevent it being freed as we evaluate whether or not we need to preempt. Fixes: df403069029d ("drm/i915/execlists: Lift process_csb() out of the irq-off spinlock") 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: Mika Kuoppala <mika.kuoppala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191104090158.2959-2-chris@chris-wilson.co.uk (cherry picked from commit 7d148635253328dda7cfe55d57e3c828e9564427) Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> (cherry picked from commit 8eb4704b124cbd44f189709959137d77063ecfa1) (cherry picked from commit 7e27238e149ce4f00d9cd801fe3aa0ea55e986a2) Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
-rw-r--r--drivers/gpu/drm/i915/i915_scheduler.c50
1 files changed, 39 insertions, 11 deletions
diff --git a/drivers/gpu/drm/i915/i915_scheduler.c b/drivers/gpu/drm/i915/i915_scheduler.c
index 7b84ebca2901..3eba8a2b39c2 100644
--- a/drivers/gpu/drm/i915/i915_scheduler.c
+++ b/drivers/gpu/drm/i915/i915_scheduler.c
@@ -177,9 +177,37 @@ static inline int rq_prio(const struct i915_request *rq)
return rq->sched.attr.priority | __NO_PREEMPTION;
}
-static void kick_submission(struct intel_engine_cs *engine, int prio)
+static inline bool need_preempt(int prio, int active)
{
- const struct i915_request *inflight = *engine->execlists.active;
+ /*
+ * Allow preemption of low -> normal -> high, but we do
+ * not allow low priority tasks to preempt other low priority
+ * tasks under the impression that latency for low priority
+ * tasks does not matter (as much as background throughput),
+ * so kiss.
+ */
+ return prio >= max(I915_PRIORITY_NORMAL, active);
+}
+
+static void kick_submission(struct intel_engine_cs *engine,
+ const struct i915_request *rq,
+ int prio)
+{
+ const struct i915_request *inflight;
+
+ /*
+ * We only need to kick the tasklet once for the high priority
+ * new context we add into the queue.
+ */
+ if (prio <= engine->execlists.queue_priority_hint)
+ return;
+
+ rcu_read_lock();
+
+ /* Nothing currently active? We're overdue for a submission! */
+ inflight = execlists_active(&engine->execlists);
+ if (!inflight)
+ goto unlock;
/*
* If we are already the currently executing context, don't
@@ -188,10 +216,15 @@ static void kick_submission(struct intel_engine_cs *engine, int prio)
* tasklet, i.e. we have not change the priority queue
* sufficiently to oust the running context.
*/
- if (!inflight || !i915_scheduler_need_preempt(prio, rq_prio(inflight)))
- return;
+ if (inflight->hw_context == rq->hw_context)
+ goto unlock;
- tasklet_hi_schedule(&engine->execlists.tasklet);
+ engine->execlists.queue_priority_hint = prio;
+ if (need_preempt(prio, rq_prio(inflight)))
+ tasklet_hi_schedule(&engine->execlists.tasklet);
+
+unlock:
+ rcu_read_unlock();
}
static void __i915_schedule(struct i915_sched_node *node,
@@ -317,13 +350,8 @@ static void __i915_schedule(struct i915_sched_node *node,
list_move_tail(&node->link, cache.priolist);
}
- if (prio <= engine->execlists.queue_priority_hint)
- continue;
-
- engine->execlists.queue_priority_hint = prio;
-
/* Defer (tasklet) submission until after all of our updates. */
- kick_submission(engine, prio);
+ kick_submission(engine, node_to_request(node), prio);
}
spin_unlock(&engine->active.lock);