From da114d501322fe2f1698d19a11d6dc298000dfe4 Mon Sep 17 00:00:00 2001 From: emersion Date: Thu, 14 Jun 2018 10:15:14 +0100 Subject: [PATCH] buffer: don't destroy DMA-BUF textures with wl_buffer After some discussions on #wayland, it seems that as soon as you hold a reference to a DMA-BUF (via EGLImage for instance), the underlying memory won't get free'd. The client is allowed to re-use the DMA-BUF and upload something else to it though. --- types/wlr_buffer.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/types/wlr_buffer.c b/types/wlr_buffer.c index 82a359f0..ccff7b46 100644 --- a/types/wlr_buffer.c +++ b/types/wlr_buffer.c @@ -43,11 +43,12 @@ static void buffer_resource_handle_destroy(struct wl_listener *listener, wl_list_init(&buffer->resource_destroy.link); buffer->resource = NULL; - if (!buffer->released) { - // The texture becomes invalid - wlr_texture_destroy(buffer->texture); - buffer->texture = NULL; - } + // At this point, if the wl_buffer comes from linux-dmabuf or wl_drm, we + // still haven't released it (ie. we'll read it in the future) but the + // client destroyed it. Reading the texture itself should be fine because + // we still hold a reference to the DMA-BUF via the texture. However the + // client could decide to re-use the same DMA-BUF for something else, in + // which case we'll read garbage. We decide to accept this risk. } struct wlr_buffer *wlr_buffer_create(struct wlr_renderer *renderer, @@ -80,6 +81,10 @@ struct wlr_buffer *wlr_buffer_create(struct wlr_renderer *renderer, struct wlr_dmabuf_buffer *dmabuf = wlr_dmabuf_buffer_from_buffer_resource(resource); texture = wlr_texture_from_dmabuf(renderer, &dmabuf->attributes); + + // We have imported the DMA-BUF, but we need to prevent the client from + // re-using the same DMA-BUF for the next frames, so we don't release + // the buffer yet. } else { wlr_log(L_ERROR, "Cannot upload texture: unknown buffer type"); return NULL;