xf86-video-intel: src/sna/sna_dri2.c

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 src/sna/sna_dri2.c |   11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

New commits:
commit e781d43dadde342a7a5b8661b8bf4690b8a1bb6e
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Wed May 6 18:56:39 2020 +0100

    sna/dri2: Prevent copying stale buffers
    
    The back buffer of window/pixmap is invalidated by DRI2ScheduleSwap, and
    is not available until the client calls DRI2GetBuffers. If they try to
    use their old handles, they will only get stale data. Similarly if they
    ask us to DRI2CopyRegion before the GetBuffers has reallocated a new
    back buffer, that back buffer is stale. Since the back buffer is
    out-of-date [likely containing data from a couple of swaps ago], we
    should ignore the copy to avoid glitching [by hopefully having a less
    noticeable glitch!] It's not entirely clear what the client intended at
    this point...
    
    Closes: https://gitlab.freedesktop.org/xorg/driver/xf86-video-intel/-/issues/195
    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

diff --git a/src/sna/sna_dri2.c b/src/sna/sna_dri2.c
index f2f2c1d3..4ee76627 100644
--- a/src/sna/sna_dri2.c
+++ b/src/sna/sna_dri2.c
@@ -1421,25 +1421,30 @@ sna_dri2_copy_region(DrawablePtr draw,
 	PixmapPtr pixmap = get_drawable_pixmap(draw);
 	struct sna *sna = to_sna_from_pixmap(pixmap);
 
-	DBG(("%s: pixmap=%ld, src=%u (refs=%d/%d, flush=%d, attach=%d) , dst=%u (refs=%d/%d, flush=%d, attach=%d)\n",
+	DBG(("%s: pixmap=%ld, src=%u (attach=%d, refs=%d/%d, flush=%d, stale=%d) , dst=%u (attach=%d, refs=%d/%d, flush=%d, stale=%d)\n",
 	     __FUNCTION__,
 	     pixmap->drawable.serialNumber,
 	     get_private(src)->bo->handle,
+	     src->attachment,
 	     get_private(src)->refcnt,
 	     get_private(src)->bo->refcnt,
 	     get_private(src)->bo->flush,
-	     src->attachment,
+	     get_private(src)->stale,
 	     get_private(dst)->bo->handle,
+	     dst->attachment,
 	     get_private(dst)->refcnt,
 	     get_private(dst)->bo->refcnt,
 	     get_private(dst)->bo->flush,
-	     dst->attachment));
+	     get_private(dst)->stale));
 
 	assert(src != dst);
 
 	assert(get_private(src)->refcnt);
 	assert(get_private(dst)->refcnt);
 
+	if (get_private(src)->stale)
+		return;
+
 	assert(get_private(src)->bo != get_private(dst)->bo);
 
 	assert(get_private(src)->bo->refcnt);