Mesa (staging/19.3): radeonsi: make si_fence_server_signal flush pipe without work

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Module: Mesa
Branch: staging/19.3
Commit: b81f4a4092b0e4091e728ec50606dc6561963fba
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=b81f4a4092b0e4091e728ec50606dc6561963fba

Author: Peng Huang <shawn.p.huang at gmail.com>
Date:   Sat Feb  1 22:31:00 2020 -0500

radeonsi: make si_fence_server_signal flush pipe without work

glSignalSemaphoreEXT sometime doesn't signal the semaphore, it is
because radeonsi doesn't flush if gl context doesn't have pending
work. Fix the porblem by always submit ib.

Reviewed-by: Marek Olšák <marek.olsak at amd.com>
Cc: 19.3 20.0 <mesa-stable at lists.freedesktop.org>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3779>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3779>
(cherry picked from commit 0660cbf4262891e6380faf0d99217b2d27873051)

---

 .pick_status.json                       | 2 +-
 src/gallium/drivers/radeonsi/si_fence.c | 4 ++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/.pick_status.json b/.pick_status.json
index e00110723a4..947691e2196 100644
--- a/.pick_status.json
+++ b/.pick_status.json
@@ -274,7 +274,7 @@
         "description": "radeonsi: make si_fence_server_signal flush pipe without work",
         "nominated": true,
         "nomination_type": 0,
-        "resolution": 0,
+        "resolution": 1,
         "master_sha": null,
         "because_sha": null
     },
diff --git a/src/gallium/drivers/radeonsi/si_fence.c b/src/gallium/drivers/radeonsi/si_fence.c
index 4df9e65dd08..dcd16b9d11e 100644
--- a/src/gallium/drivers/radeonsi/si_fence.c
+++ b/src/gallium/drivers/radeonsi/si_fence.c
@@ -606,7 +606,11 @@ static void si_fence_server_signal(struct pipe_context *ctx,
 	 * Therefore, we must make sure that we flush the pipe to avoid
 	 * new work being emitted and getting executed before the signal
 	 * operation.
+	 * 
+	 * Set sctx->initial_gfx_cs_size to force IB submission even if
+	 * it is empty.
 	 */
+	sctx->initial_gfx_cs_size = 0;
 	si_flush_from_st(ctx, NULL, PIPE_FLUSH_ASYNC);
 }