[PATCH 2/2] DRI2SwapBuffers: Fix uninitialized target SBC.
Jamey Sharp
jamey at minilop.net
Fri Apr 18 12:22:19 PDT 2014
Fixes Piglit test "swapbuffersmsc-return swap_interval 0".
Ensure that *swap_target gets initialized on any 'return Success' path,
even if the swap request can't be completed by the driver and the server
falls back to a simple blit. That path can also be triggered by setting
swap_interval to 0, which disables sync to vertical retrace.
We originally found this bug because for some reason SDL2 automatically
sets swap_interval to 0, when we were trying to test OML_sync_control in
an SDL2 test application. We then discovered that the above-mentioned
Piglit test has been failing for the same reason since it was
introduced.
Signed-off-by: Jamey Sharp <jamey at minilop.net>
Signed-off-by: Theo Hill <Theo0x48 at gmail.com>
---
hw/xfree86/dri2/dri2.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/hw/xfree86/dri2/dri2.c b/hw/xfree86/dri2/dri2.c
index 962f40c..76708ca 100644
--- a/hw/xfree86/dri2/dri2.c
+++ b/hw/xfree86/dri2/dri2.c
@@ -1092,6 +1092,14 @@ DRI2SwapBuffers(ClientPtr client, DrawablePtr pDraw, CARD64 target_msc,
return BadDrawable;
}
+ /* According to spec, return expected swapbuffers count SBC after this swap
+ * will complete. This is ignored unless we return Success, but it must be
+ * initialized on every path where we return Success or the caller will send
+ * an uninitialized value off the stack to the client. So let's initialize
+ * it as early as possible, just to be sure.
+ */
+ *swap_target = pPriv->swap_count + pPriv->swapsPending + 1;
+
for (i = 0; i < pPriv->bufferCount; i++) {
if (pPriv->buffers[i]->attachment == DRI2BufferFrontLeft)
pDestBuffer = (DRI2BufferPtr) pPriv->buffers[i];
@@ -1165,11 +1173,6 @@ DRI2SwapBuffers(ClientPtr client, DrawablePtr pDraw, CARD64 target_msc,
pPriv->last_swap_target = target_msc;
- /* According to spec, return expected swapbuffers count SBC after this swap
- * will complete.
- */
- *swap_target = pPriv->swap_count + pPriv->swapsPending;
-
DRI2InvalidateDrawableAll(pDraw);
return Success;
--
1.8.5.3
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