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DRI2SwapBuffers: Fix uninitialized target SBC.

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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@minilop.net>
Signed-off-by: Theo Hill <Theo0x48@gmail.com>
Reviewed-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Keith Packard <keithp@keithp.com>
This commit is contained in:
Jamey Sharp 2014-04-18 12:22:19 -07:00 committed by Keith Packard
parent 4927af4475
commit 138bf5ac97
1 changed files with 8 additions and 5 deletions
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13
hw/xfree86/dri2/dri2.c
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@ -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;