Mario Kleiner <mario.kleiner...@gmail.com> writes:
> glXSwapBuffersMscOML() with target_msc=divisor=remainder=0 gets
> translated into target_msc=divisor=0 but remainder=1 by the mesa
> api. This is done for server DRI2 where there needs to be a way
> to tell the server-side DRI2ScheduleSwap implementation if a call
> to glXSwapBuffers() or glXSwapBuffersMscOML(dpy,window,0,0,0) was
> done. remainder = 1 was (ab)used as a flag to tell the server to
> select proper semantic. The DRI3/Present backend ignored this
> signalling, treated any target_msc=0 as glXSwapBuffers() request,
> and called xcb_present_pixmap with invalid divisor=0, remainder=1
> combo. The present extension responded kindly to this with a
> BadValue error and dropped the request, but mesa's DRI3/Present
> backend doesn't check for error codes. From there on stuff went
> downhill quickly for the calling OpenGL client...
>
> This patch fixes the problem.
>
> Cc: "10.3 10.4" <mesa-sta...@lists.freedesktop.org>
> Signed-off-by: Mario Kleiner <mario.kleiner...@gmail.com>
> ---
> src/glx/dri3_glx.c | 14 ++++++++++++--
> 1 file changed, 12 insertions(+), 2 deletions(-)
>
> diff --git a/src/glx/dri3_glx.c b/src/glx/dri3_glx.c
> index c53be1b..efff907 100644
> --- a/src/glx/dri3_glx.c
> +++ b/src/glx/dri3_glx.c
> @@ -1552,11 +1552,21 @@ dri3_swap_buffers(__GLXDRIdrawable *pdraw, int64_t
> target_msc, int64_t divisor,
> dri3_fence_reset(c, back);
>
> /* Compute when we want the frame shown by taking the last known
> successful
> - * MSC and adding in a swap interval for each outstanding swap request
> + * MSC and adding in a swap interval for each outstanding swap request.
> + * target_msc=divisor=remainder=0 means "Use glXSwapBuffers() semantic"
> */
> ++priv->send_sbc;
> - if (target_msc == 0)
> + if (target_msc == 0 && divisor == 0 && remainder == 0)
> target_msc = priv->msc + priv->swap_interval * (priv->send_sbc -
> priv->recv_sbc);
> + else if (divisor == 0 && remainder > 0) {
> + /* Special case signalling: This means "glXSwapBuffersMscOML()
> called with
> + * target_msc=divisor=remainder=0. Needed to distinguish from
> glXSwapBuffers
> + * case above. Reset remainder to zero, so PresentPixmap won't bail
> on us.
> + * GLX_OML_sync_control says for divisor == 0 any remainder >= 0 is
> fine,
> + * whereas Present extension wants remainder == 0 for divisor == 0.
> + */
> + remainder = 0;
> + }There's at least a mismatched '"' in the second comment, and I'd have thought the msc/divisor/msc==0 would be the "special case signalling" case. I'd replace the comment with: /* From the GLX_OML_sync_control spec: * * "If <divisor> = 0, the swap will occur when MSC becomes * greater than or equal to <target_msc>." * * Note that there's no mention of the remainder. The Present extension * throws BadValue for remainder != 0 with divisor == 0, so just drop * the passed in value. */ With that, Reviewed-by: Eric Anholt <e...@anholt.net>
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