EGL uses the force_copy parameter to loader_dri3_swap_buffers_msc() to indicate
that it wants to preserve back buffer contents across a buffer swap.
While the loader then turns off server-side page-flipping there's nothing to
guarantee that a new backbuffer isn't chosen when EGL starts to render again,
and that buffer's content is of course undefined.
So rework the functionality:
If the client supports local blits, allow server-side page flipping and when
a new back is grabbed, if needed, blit the old back's content to the new back.
If the client doesn't support local blits, disallow server-side page-flipping
to avoid a client deadlock and then, when grabbing a new back buffer, sleep
until the old back is idle, which may take a substantial time depending on
swap interval.
Signed-off-by: Thomas Hellstrom <thellst...@vmware.com>
---
src/loader/loader_dri3_helper.c | 55 ++++++++++++++++++++++++++++++++++++++---
src/loader/loader_dri3_helper.h | 1 +
2 files changed, 52 insertions(+), 4 deletions(-)
diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
index 6f84a43..812adcc 100644
--- a/src/loader/loader_dri3_helper.c
+++ b/src/loader/loader_dri3_helper.c
@@ -258,6 +258,7 @@ loader_dri3_drawable_init(xcb_connection_t *conn,
draw->have_image_blit = draw->ext->image->base.version >= 9 &&
draw->ext->image->blitImage != NULL;
+ draw->cur_blit_source = -1;
if (draw->ext->config)
draw->ext->config->configQueryi(draw->dri_screen,
@@ -475,12 +476,21 @@ dri3_find_back(struct loader_dri3_drawable *draw)
int b;
xcb_generic_event_t *ev;
xcb_present_generic_event_t *ge;
+ int num_to_consider = draw->num_back;
/* Increase the likelyhood of reusing current buffer */
dri3_flush_present_events(draw);
+ /* Check whether we need to reuse the current back buffer as new back.
+ * In that case, wait until it's not busy anymore.
+ */
+ if (!draw->have_image_blit && draw->cur_blit_source != -1) {
+ num_to_consider = 1;
+ draw->cur_blit_source = -1;
+ }
+
for (;;) {
- for (b = 0; b < draw->num_back; b++) {
+ for (b = 0; b < num_to_consider; b++) {
int id = LOADER_DRI3_BACK_ID((b + draw->cur_back) % draw->num_back);
struct loader_dri3_buffer *buffer = draw->buffers[id];
@@ -753,6 +763,13 @@ loader_dri3_swap_buffers_msc(struct loader_dri3_drawable
*draw,
0, 0, __BLIT_FLAG_FLUSH);
}
+ /* If we need to preload the new back buffer, remember the source.
+ * The force_copy parameter is used by EGL to attempt to preserve
+ * the back buffer across a call to this function.
+ */
+ if (force_copy)
+ draw->cur_blit_source = LOADER_DRI3_BACK_ID(draw->cur_back);
+
dri3_flush_present_events(draw);
if (back && !draw->is_pixmap) {
@@ -791,8 +808,13 @@ loader_dri3_swap_buffers_msc(struct loader_dri3_drawable
*draw,
*/
if (draw->swap_interval == 0)
options |= XCB_PRESENT_OPTION_ASYNC;
- if (force_copy)
- options |= XCB_PRESENT_OPTION_COPY;
+
+ /* If we need to populate the new back, but need to reuse the back
+ * buffer slot due to lack of local blit capabilities, make sure
+ * the server doesn't flip and we deadlock.
+ */
+ if (!draw->have_image_blit && draw->cur_blit_source != -1)
+ options |= XCB_PRESENT_OPTION_COPY;
back->busy = 1;
back->last_swap = draw->send_sbc;
@@ -1365,6 +1387,31 @@ dri3_get_buffer(__DRIdrawable *driDrawable,
}
dri3_fence_await(draw->conn, buffer);
+ /*
+ * Do we need to preserve the content of a previous buffer?
+ *
+ * Note that this blit is needed only to avoid a wait for a buffer that
+ * is currently in the flip chain or being scanned out from. That's really
+ * a tradeoff. If we're ok with the wait we can reduce the number of back
+ * buffers to 1 for SWAP_EXCHANGE, and 1 for SWAP_COPY,
+ * but in the latter case we must disallow page-flipping.
+ */
+ if (buffer_type == loader_dri3_buffer_back &&
+ draw->cur_blit_source != -1 &&
+ draw->buffers[draw->cur_blit_source] &&
+ buffer != draw->buffers[draw->cur_blit_source]) {
+
+ struct loader_dri3_buffer *source = draw->buffers[draw->cur_blit_source];
+
+ /* Avoid flushing here. Will propably do good for tiling hardware. */
+ (void) loader_dri3_blit_image(draw,
+ buffer->image,
+ source->image,
+ 0, 0, draw->width, draw->height,
+ 0, 0, 0);
+ buffer->last_swap = source->last_swap;
+ draw->cur_blit_source = -1;
+ }
/* Return the requested buffer */
return buffer;
}
@@ -1431,7 +1478,7 @@ loader_dri3_get_buffers(__DRIdrawable *driDrawable,
return false;
/* pixmaps always have front buffers */
-// if (draw->is_pixmap)
+ if (draw->is_pixmap)
buffer_mask |= __DRI_IMAGE_BUFFER_FRONT;
if (buffer_mask & __DRI_IMAGE_BUFFER_FRONT) {
diff --git a/src/loader/loader_dri3_helper.h b/src/loader/loader_dri3_helper.h
index be41da9..82c5363 100644
--- a/src/loader/loader_dri3_helper.h
+++ b/src/loader/loader_dri3_helper.h
@@ -145,6 +145,7 @@ struct loader_dri3_drawable {
struct loader_dri3_buffer *buffers[LOADER_DRI3_NUM_BUFFERS];
int cur_back;
int num_back;
+ int cur_blit_source;
uint32_t *stamp;
--
2.7.4
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