From f95d81e88be07f43c91660e675d077ccd9ee47a9 Mon Sep 17 00:00:00 2001 From: Olivier Fourdan Date: Mon, 7 Dec 2020 14:21:56 +0100 Subject: [PATCH] xwayland: Hold window buffer until released MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The window buffer mechanism would free the pixmap and its corresponding Wayland buffer as soon as window buffers are disposed. Typically when the X11 window is unrealized, the current window buffer is still used by the Wayland compositor and yet Xwayland will destroy the buffer. As a matter of fact, Xwayland should not destroy the Wayland buffer before the wl_buffer.release event is received. Add a reference counter to the window buffer similar to the to pixmap reference counter to keep the buffer around until the release callback is received. Increase that reference counter on the buffer which will be attached to the surface, and drop that reference when receiving the release callback notification. v2: Use a specific reference counter on the buffer rather than relying on the pixmap refcnt (Michel Dänzer ) Signed-off-by: Olivier Fourdan Reviewed-by: Michel Dänzer Acked-by: Martin Peres --- hw/xwayland/xwayland-window-buffers.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/hw/xwayland/xwayland-window-buffers.c b/hw/xwayland/xwayland-window-buffers.c index 7336a7fbe..f04c79a8a 100644 --- a/hw/xwayland/xwayland-window-buffers.c +++ b/hw/xwayland/xwayland-window-buffers.c @@ -40,6 +40,7 @@ struct xwl_window_buffer { PixmapPtr pixmap; RegionPtr damage_region; Bool recycle_on_release; + int refcnt; uint32_t time; struct xorg_list link_buffer; }; @@ -79,6 +80,7 @@ xwl_window_buffer_new(struct xwl_window *xwl_window) xwl_window_buffer->xwl_window = xwl_window; xwl_window_buffer->damage_region = RegionCreate(NullBox, 1); xwl_window_buffer->pixmap = NullPixmap; + xwl_window_buffer->refcnt = 1; xorg_list_append(&xwl_window_buffer->link_buffer, &xwl_window->window_buffers_available); @@ -96,9 +98,14 @@ xwl_window_buffer_destroy_pixmap(struct xwl_window_buffer *xwl_window_buffer) xwl_window_buffer->pixmap = NullPixmap; } -static void +static Bool xwl_window_buffer_dispose(struct xwl_window_buffer *xwl_window_buffer) { + assert(xwl_window_buffer->refcnt > 0); + + if (--xwl_window_buffer->refcnt) + return FALSE; + RegionDestroy(xwl_window_buffer->damage_region); if (xwl_window_buffer->pixmap) @@ -106,6 +113,8 @@ xwl_window_buffer_dispose(struct xwl_window_buffer *xwl_window_buffer) xorg_list_del(&xwl_window_buffer->link_buffer); free(xwl_window_buffer); + + return TRUE; } static void @@ -187,6 +196,12 @@ xwl_window_buffer_release_callback(void *data) struct xwl_window *xwl_window = xwl_window_buffer->xwl_window; struct xwl_window_buffer *oldest_available_buffer; + /* Drop the reference on the buffer we took in get_pixmap. If that + * frees the window buffer, we're done. + */ + if (xwl_window_buffer_dispose(xwl_window_buffer)) + return; + if (xwl_window_buffer->recycle_on_release) xwl_window_buffer_recycle(xwl_window_buffer); @@ -250,15 +265,21 @@ xwl_window_buffers_dispose(struct xwl_window *xwl_window) { struct xwl_window_buffer *xwl_window_buffer, *tmp; + /* This is called prior to free the xwl_window, make sure to untie + * the buffers from the xwl_window so that we don't point at freed + * memory if we get a release buffer later. + */ xorg_list_for_each_entry_safe(xwl_window_buffer, tmp, &xwl_window->window_buffers_available, link_buffer) { + xorg_list_del(&xwl_window_buffer->link_buffer); xwl_window_buffer_dispose(xwl_window_buffer); } xorg_list_for_each_entry_safe(xwl_window_buffer, tmp, &xwl_window->window_buffers_unavailable, link_buffer) { + xorg_list_del(&xwl_window_buffer->link_buffer); xwl_window_buffer_dispose(xwl_window_buffer); } @@ -329,6 +350,8 @@ xwl_window_buffers_get_pixmap(struct xwl_window *xwl_window, RegionEmpty(xwl_window_buffer->damage_region); + /* Hold a reference on the buffer until it's released by the compositor */ + xwl_window_buffer->refcnt++; xwl_pixmap_set_buffer_release_cb(xwl_window_buffer->pixmap, xwl_window_buffer_release_callback, xwl_window_buffer);