[Mesa-dev] [PATCH 2/5] winsys/radeon: remove cs_queue_empty

[Christian König]

From: Christian König <christian.koenig at amd.com>

Waiting for an empty queue is nonsense and can lead to deadlocks if we have
multiple waiters or another thread that continuously sends down new commands.

Just post the cs to the queue and immediately wait for it to finish.

This is a candidate for the stable branch.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 src/gallium/winsys/radeon/drm/radeon_drm_cs.c     | 11 +++--------
 src/gallium/winsys/radeon/drm/radeon_drm_winsys.c |  6 ------
 src/gallium/winsys/radeon/drm/radeon_drm_winsys.h |  5 -----
 3 files changed, 3 insertions(+), 19 deletions(-)

diff --git a/src/gallium/winsys/radeon/drm/radeon_drm_cs.c b/src/gallium/winsys/radeon/drm/radeon_drm_cs.c
index 38a9209..d530011 100644
--- a/src/gallium/winsys/radeon/drm/radeon_drm_cs.c
+++ b/src/gallium/winsys/radeon/drm/radeon_drm_cs.c
@@ -560,17 +560,12 @@ static void radeon_drm_cs_flush(struct radeon_winsys_cs *rcs, unsigned flags, ui
             break;
         }
 
-        if (cs->ws->thread && (flags & RADEON_FLUSH_ASYNC)) {
+        if (cs->ws->thread) {
             cs->flush_started = 1;
             radeon_drm_ws_queue_cs(cs->ws, cs);
+            if (!(flags & RADEON_FLUSH_ASYNC))
+                radeon_drm_cs_sync_flush(rcs);
         } else {
-            pipe_mutex_lock(cs->ws->cs_stack_lock);
-            if (cs->ws->thread) {
-                while (p_atomic_read(&cs->ws->ncs)) {
-                    pipe_condvar_wait(cs->ws->cs_queue_empty, cs->ws->cs_stack_lock);
-                }
-            }
-            pipe_mutex_unlock(cs->ws->cs_stack_lock);
             radeon_drm_cs_emit_ioctl_oneshot(cs, cs->cst);
         }
     } else {
diff --git a/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c b/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c
index 0a3b932..27bf348 100644
--- a/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c
+++ b/src/gallium/winsys/radeon/drm/radeon_drm_winsys.c
@@ -431,7 +431,6 @@ static void radeon_winsys_destroy(struct radeon_winsys *rws)
         pipe_thread_wait(ws->thread);
     }
     pipe_semaphore_destroy(&ws->cs_queued);
-    pipe_condvar_destroy(ws->cs_queue_empty);
 
     pipe_mutex_destroy(ws->hyperz_owner_mutex);
     pipe_mutex_destroy(ws->cmask_owner_mutex);
@@ -567,9 +566,6 @@ next:
             }
             ws->cs_stack[p_atomic_read(&ws->ncs) - 1] = NULL;
             empty_stack = p_atomic_dec_zero(&ws->ncs);
-            if (empty_stack) {
-                pipe_condvar_signal(ws->cs_queue_empty);
-            }
             pipe_mutex_unlock(ws->cs_stack_lock);
 
             pipe_semaphore_signal(&cs->flush_completed);
@@ -585,7 +581,6 @@ next:
         ws->cs_stack[i] = NULL;
     }
     p_atomic_set(&ws->ncs, 0);
-    pipe_condvar_signal(ws->cs_queue_empty);
     pipe_mutex_unlock(ws->cs_stack_lock);
     return NULL;
 }
@@ -651,7 +646,6 @@ struct radeon_winsys *radeon_drm_winsys_create(int fd)
 
     p_atomic_set(&ws->ncs, 0);
     pipe_semaphore_init(&ws->cs_queued, 0);
-    pipe_condvar_init(ws->cs_queue_empty);
     if (ws->num_cpus > 1 && debug_get_option_thread())
         ws->thread = pipe_thread_create(radeon_drm_cs_emit_ioctl, ws);
 
diff --git a/src/gallium/winsys/radeon/drm/radeon_drm_winsys.h b/src/gallium/winsys/radeon/drm/radeon_drm_winsys.h
index 682479e..ed90194 100644
--- a/src/gallium/winsys/radeon/drm/radeon_drm_winsys.h
+++ b/src/gallium/winsys/radeon/drm/radeon_drm_winsys.h
@@ -67,11 +67,6 @@ struct radeon_drm_winsys {
     /* rings submission thread */
     pipe_mutex cs_stack_lock;
     pipe_semaphore cs_queued;
-    /* we cannot use semaphore for empty queue because maintaining an even
-     * number of call to semaphore_wait and semaphore_signal is, to say the
-     * least, tricky
-     */
-    pipe_condvar cs_queue_empty;
     pipe_thread thread;
     int kill_thread;
     int ncs;
-- 
1.8.1.2