Stefan Dösinger : wined3d: Do not call queue_is_empty in wined3d_cs_mt_finish.

[Alexandre Julliard]

Module: wine
Branch: master
Commit: 55eee0b9f155c1f70ff92549e22ef7984ac6b534
URL:    http://source.winehq.org/git/wine.git/?a=commit;h=55eee0b9f155c1f70ff92549e2...

Author: Stefan Dösinger 
Date:   Sun Aug 27 23:22:42 2017 +0200

wined3d: Do not call queue_is_empty in wined3d_cs_mt_finish.

Without an explicit volatile, aarch64 gcc will copy queue->tail into a
register outside the loop and then continuously compare two registers
against each other. The *(volatile LONG *)& forces gcc to re-read the
memory every iteration. Therefore, queue_is_empty as it is written will
only work from the CS thread.

Signed-off-by: Stefan Dösinger 
Signed-off-by: Henri Verbeet 
Signed-off-by: Alexandre Julliard

---

dlls/wined3d/cs.c              | 13 +++++++------
 dlls/wined3d/wined3d_private.h |  2 +-
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/dlls/wined3d/cs.c b/dlls/wined3d/cs.c
index 4a405d0..bef4795 100644
--- a/dlls/wined3d/cs.c
+++ b/dlls/wined3d/cs.c
@@ -2413,8 +2413,9 @@ static const struct wined3d_cs_ops wined3d_cs_st_ops =
     wined3d_cs_st_push_constants,
 };

-static BOOL wined3d_cs_queue_is_empty(const struct wined3d_cs_queue *queue)
+static BOOL wined3d_cs_queue_is_empty(const struct wined3d_cs *cs, const struct wined3d_cs_queue *queue)
 {
+    wined3d_from_cs(cs);
     return *(volatile LONG *)&queue->head == queue->tail;
 }

@@ -2513,7 +2514,7 @@ static void wined3d_cs_mt_finish(struct wined3d_cs *cs, enum wined3d_cs_queue_id
     if (cs->thread_id == GetCurrentThreadId())
         return wined3d_cs_st_finish(cs, queue_id);

-    while (!wined3d_cs_queue_is_empty(&cs->queue[queue_id]))
+    while (cs->queue[queue_id].head != *(volatile LONG *)&cs->queue[queue_id].tail)
         wined3d_pause();
 }

@@ -2551,8 +2552,8 @@ static void wined3d_cs_wait_event(struct wined3d_cs *cs)
      * Likewise, we can race with the main thread when resetting
      * "waiting_for_event", in which case we would need to call
      * WaitForSingleObject() because the main thread called SetEvent(). */
-    if (!(wined3d_cs_queue_is_empty(&cs->queue[WINED3D_CS_QUEUE_DEFAULT])
-            && wined3d_cs_queue_is_empty(&cs->queue[WINED3D_CS_QUEUE_MAP]))
+    if (!(wined3d_cs_queue_is_empty(cs, &cs->queue[WINED3D_CS_QUEUE_DEFAULT])
+            && wined3d_cs_queue_is_empty(cs, &cs->queue[WINED3D_CS_QUEUE_MAP]))
             && InterlockedCompareExchange(&cs->waiting_for_event, FALSE, TRUE))
         return;

@@ -2582,10 +2583,10 @@ static DWORD WINAPI wined3d_cs_run(void *ctx)
         }

queue = &cs->queue[WINED3D_CS_QUEUE_MAP];
-        if (wined3d_cs_queue_is_empty(queue))
+        if (wined3d_cs_queue_is_empty(cs, queue))
         {
             queue = &cs->queue[WINED3D_CS_QUEUE_DEFAULT];
-            if (wined3d_cs_queue_is_empty(queue))
+            if (wined3d_cs_queue_is_empty(cs, queue))
             {
                 if (++spin_count >= WINED3D_CS_SPIN_COUNT && list_empty(&cs->query_poll_list))
                     wined3d_cs_wait_event(cs);
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index 74043d0..1a196a5 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -4277,7 +4277,7 @@ static inline struct wined3d_surface *context_get_rt_surface(const struct wined3
     return texture->sub_resources[context->current_rt.sub_resource_idx].u.surface;
 }

-static inline void wined3d_from_cs(struct wined3d_cs *cs)
+static inline void wined3d_from_cs(const struct wined3d_cs *cs)
 {
     if (cs->thread)
         assert(cs->thread_id == GetCurrentThreadId());