In the next patch, we will begin processing the CSB from inside the
interrupt handler. This means that updating the execlists->port[] will
no longer be locked by the tasklet but by the engine->timeline.lock
instead. Pull dequeue and submit under the same lock for protection.
(An alternative, future, plan is to keep the in/out arrays separate for
concurrent processing and reduced lock coverage.)

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_lrc.c | 32 ++++++++++++--------------------
 1 file changed, 12 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index ea85e2a50b83..703135637798 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -562,7 +562,7 @@ static void complete_preempt_context(struct 
intel_engine_execlists *execlists)
        execlists_clear_active(execlists, EXECLISTS_ACTIVE_PREEMPT);
 }
 
-static bool __execlists_dequeue(struct intel_engine_cs *engine)
+static void __execlists_dequeue(struct intel_engine_cs *engine)
 {
        struct intel_engine_execlists * const execlists = &engine->execlists;
        struct execlist_port *port = execlists->port;
@@ -617,11 +617,11 @@ static bool __execlists_dequeue(struct intel_engine_cs 
*engine)
                 * the HW to indicate that it has had a chance to respond.
                 */
                if (!execlists_is_active(execlists, EXECLISTS_ACTIVE_HWACK))
-                       return false;
+                       return;
 
                if (need_preempt(engine, last, execlists->queue_priority)) {
                        inject_preempt_context(engine);
-                       return false;
+                       return;
                }
 
                /*
@@ -646,7 +646,7 @@ static bool __execlists_dequeue(struct intel_engine_cs 
*engine)
                 * priorities of the ports haven't been switch.
                 */
                if (port_count(&port[1]))
-                       return false;
+                       return;
 
                /*
                 * WaIdleLiteRestore:bdw,skl
@@ -746,8 +746,10 @@ static bool __execlists_dequeue(struct intel_engine_cs 
*engine)
                port != execlists->port ? rq_prio(last) : INT_MIN;
 
        execlists->first = rb;
-       if (submit)
+       if (submit) {
                port_assign(port, last);
+               execlists_submit_ports(engine);
+       }
 
        /* We must always keep the beast fed if we have work piled up */
        GEM_BUG_ON(execlists->first && !port_isset(execlists->port));
@@ -756,24 +758,19 @@ static bool __execlists_dequeue(struct intel_engine_cs 
*engine)
        if (last)
                execlists_user_begin(execlists, execlists->port);
 
-       return submit;
+       /* If the engine is now idle, so should be the flag; and vice versa. */
+       GEM_BUG_ON(execlists_is_active(&engine->execlists,
+                                      EXECLISTS_ACTIVE_USER) ==
+                  !port_isset(engine->execlists.port));
 }
 
 static void execlists_dequeue(struct intel_engine_cs *engine)
 {
-       struct intel_engine_execlists * const execlists = &engine->execlists;
        unsigned long flags;
-       bool submit;
 
        spin_lock_irqsave(&engine->timeline.lock, flags);
-       submit = __execlists_dequeue(engine);
+       __execlists_dequeue(engine);
        spin_unlock_irqrestore(&engine->timeline.lock, flags);
-
-       if (submit)
-               execlists_submit_ports(engine);
-
-       GEM_BUG_ON(port_isset(execlists->port) &&
-                  !execlists_is_active(execlists, EXECLISTS_ACTIVE_USER));
 }
 
 void
@@ -1156,11 +1153,6 @@ static void execlists_submission_tasklet(unsigned long 
data)
 
        if (!execlists_is_active(&engine->execlists, EXECLISTS_ACTIVE_PREEMPT))
                execlists_dequeue(engine);
-
-       /* If the engine is now idle, so should be the flag; and vice versa. */
-       GEM_BUG_ON(execlists_is_active(&engine->execlists,
-                                      EXECLISTS_ACTIVE_USER) ==
-                  !port_isset(engine->execlists.port));
 }
 
 static void queue_request(struct intel_engine_cs *engine,
-- 
2.17.0

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