drm/i915/gt: Flush other retirees inside intel_gt_retire_requests()

Our goal in wait_for_idle (intel_gt_retire_requests) is to the current
workload *and* their idle barriers. This requires us to notice the late
arrival of those, which is done by inspecting the list of active
timelines. However, if a concurrent retirer is running that new timeline
may not be added until after we drop the lock -- so flush concurrent
retirers before we take the lock and inspect the list.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/878
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Acked-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191223211008.2371613-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_engine.h b/drivers/gpu/drm/i915/gt/intel_engine.h
index 79ecac5..71f1bcd 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_engine.h
+++ b/drivers/gpu/drm/i915/gt/intel_engine.h
@@ -282,7 +282,7 @@ static inline void __intel_engine_reset(struct intel_engine_cs *engine,
 
 bool intel_engines_are_idle(struct intel_gt *gt);
 bool intel_engine_is_idle(struct intel_engine_cs *engine);
-bool intel_engine_flush_submission(struct intel_engine_cs *engine);
+void intel_engine_flush_submission(struct intel_engine_cs *engine);
 
 void intel_engines_reset_default_submission(struct intel_gt *gt);
 

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index ddf9543..825c94e 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -1047,10 +1047,9 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
        return idle;
 }
 
-bool intel_engine_flush_submission(struct intel_engine_cs *engine)
+void intel_engine_flush_submission(struct intel_engine_cs *engine)
 {
        struct tasklet_struct *t = &engine->execlists.tasklet;
-       bool active = tasklet_is_locked(t);
 
        if (__tasklet_is_scheduled(t)) {
                local_bh_disable();
@@ -1061,13 +1060,10 @@ bool intel_engine_flush_submission(struct intel_engine_cs *engine)
                        tasklet_unlock(t);
                }
                local_bh_enable();
-               active = true;
        }
 
        /* Otherwise flush the tasklet if it was running on another cpu */
        tasklet_unlock_wait(t);
-
-       return active;
 }
 
 /**

diff --git a/drivers/gpu/drm/i915/gt/intel_gt_requests.c b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
index 9e75fa1..fc691c1 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_gt_requests.c
+++ b/drivers/gpu/drm/i915/gt/intel_gt_requests.c
@@ -26,21 +26,18 @@ static bool retire_requests(struct intel_timeline *tl)
        return !i915_active_fence_isset(&tl->last_request);
 }
 
-static bool flush_submission(struct intel_gt *gt)
+static void flush_submission(struct intel_gt *gt)
 {
        struct intel_engine_cs *engine;
        enum intel_engine_id id;
-       bool active = false;
 
        if (!intel_gt_pm_is_awake(gt))
-               return false;
+               return;
 
        for_each_engine(engine, gt, id) {
-               active |= intel_engine_flush_submission(engine);
-               active |= flush_work(&engine->retire_work);
+               intel_engine_flush_submission(engine);
+               flush_work(&engine->retire_work);
        }
-
-       return active;
 }
 
 static void engine_retire(struct work_struct *work)
@@ -126,7 +123,6 @@ long intel_gt_retire_requests_timeout(struct intel_gt *gt, long timeout)
                timeout = -timeout, interruptible = false;
 
        flush_submission(gt); /* kick the ksoftirqd tasklets */
-
        spin_lock(&timelines->lock);
        list_for_each_entry_safe(tl, tn, &timelines->active_list, link) {
                if (!mutex_trylock(&tl->mutex)) {
@@ -153,6 +149,7 @@ long intel_gt_retire_requests_timeout(struct intel_gt *gt, long timeout)
 
                active_count += !retire_requests(tl);
 
+               flush_submission(gt); /* sync with concurrent retirees */
                spin_lock(&timelines->lock);
 
                /* Resume iteration after dropping lock */
@@ -173,9 +170,6 @@ long intel_gt_retire_requests_timeout(struct intel_gt *gt, long timeout)
        list_for_each_entry_safe(tl, tn, &free, link)
                __intel_timeline_free(&tl->kref);
 
-       if (flush_submission(gt))
-               active_count++;
-
        return active_count ? timeout : 0;
 }