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DRI2SwapBuffers: Don't reuse swap_target variable. 

swap_target is an out-parameter that needs to be set to the value that
SBC will take on after this SwapBuffers request completes.

However, it was also being used as a temporary variable to hold the MSC
at which the SwapBuffers request got scheduled to occur. This confusion
makes it harder to reason about whether swap_target is being set
correctly for its out-parameter usage. (Hint: It isn't.)

For the latter use, it makes more sense to use the existing target_msc
variable, which already has the right value unless target_msc, divisor,
and remainder are all 0, in which case we can set it using swap_interval
as usual.

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 12:22:18 -07:00 committed by Keith Packard
parent c7011249d2
commit 4927af4475
1 changed files with 3 additions and 7 deletions
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10
hw/xfree86/dri2/dri2.c
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@ -1149,17 +1149,13 @@ DRI2SwapBuffers(ClientPtr client, DrawablePtr pDraw, CARD64 target_msc,
* we have to account for the current swap count, interval, and the * we have to account for the current swap count, interval, and the
* number of pending swaps. * number of pending swaps.
*/ */
*swap_target = pPriv->last_swap_target + pPriv->swap_interval; target_msc = pPriv->last_swap_target + pPriv->swap_interval;
} }
else {
/* glXSwapBuffersMscOML could have a 0 target_msc, honor it */
*swap_target = target_msc;
}
pPriv->swapsPending++; pPriv->swapsPending++;
ret = (*ds->ScheduleSwap) (client, pDraw, pDestBuffer, pSrcBuffer, ret = (*ds->ScheduleSwap) (client, pDraw, pDestBuffer, pSrcBuffer,
swap_target, divisor, remainder, func, data); &target_msc, divisor, remainder, func, data);
if (!ret) { if (!ret) {
pPriv->swapsPending--; /* didn't schedule */ pPriv->swapsPending--; /* didn't schedule */
xf86DrvMsg(pScreen->myNum, X_ERROR, xf86DrvMsg(pScreen->myNum, X_ERROR,
@ -1167,7 +1163,7 @@ DRI2SwapBuffers(ClientPtr client, DrawablePtr pDraw, CARD64 target_msc,
return BadDrawable; return BadDrawable;
} }
pPriv->last_swap_target = *swap_target; pPriv->last_swap_target = target_msc;
/* According to spec, return expected swapbuffers count SBC after this swap /* According to spec, return expected swapbuffers count SBC after this swap
* will complete. * will complete.