From 2367d78c3c1de2428cbbf9444d6eff632698baf6 Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Sat, 14 Feb 2026 18:17:32 +0100
Subject: [PATCH] render/vulkan: fix missing DMA-BUF implicit write fence for
 render buffer

Same as previous commit for the read side, but this one waits for
all readers to be done before starting to write.
---
 include/render/vulkan.h  |  2 ++
 render/vulkan/pass.c     | 40 +++++++++++++++++++++++++++++++++++++++-
 render/vulkan/renderer.c |  6 ++++++
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/include/render/vulkan.h b/include/render/vulkan.h
index a1d1c2646..903d1c33e 100644
--- a/include/render/vulkan.h
+++ b/include/render/vulkan.h
@@ -477,6 +477,8 @@ bool vulkan_sync_render_pass_release(struct wlr_vk_renderer *renderer,
 	struct wlr_vk_render_pass *pass);
 bool vulkan_sync_foreign_texture_acquire(struct wlr_vk_texture *texture,
 	int sync_file_fds[static WLR_DMABUF_MAX_PLANES]);
+bool vulkan_sync_render_buffer_acquire(struct wlr_vk_render_buffer *render_buffer,
+	int sync_file_fds[static WLR_DMABUF_MAX_PLANES]);
 
 bool vulkan_read_pixels(struct wlr_vk_renderer *vk_renderer,
 	VkFormat src_format, VkImage src_image,
diff --git a/render/vulkan/pass.c b/render/vulkan/pass.c
index 0539bae1d..503e37c07 100644
--- a/render/vulkan/pass.c
+++ b/render/vulkan/pass.c
@@ -146,6 +146,40 @@ static VkSemaphore render_pass_wait_sync_file(struct wlr_vk_render_pass *pass,
 	return *sem_ptr;
 }
 
+static bool render_pass_wait_render_buffer(struct wlr_vk_render_pass *pass,
+		VkSemaphoreSubmitInfoKHR *render_wait, uint32_t *render_wait_len_ptr) {
+	int sync_file_fds[WLR_DMABUF_MAX_PLANES];
+	for (size_t i = 0; i < WLR_DMABUF_MAX_PLANES; i++) {
+		sync_file_fds[i] = -1;
+	}
+
+	if (!vulkan_sync_render_buffer_acquire(pass->render_buffer, sync_file_fds)) {
+		return false;
+	}
+
+	for (size_t i = 0; i < WLR_DMABUF_MAX_PLANES; i++) {
+		if (sync_file_fds[i] < 0) {
+			continue;
+		}
+
+		VkSemaphore sem = render_pass_wait_sync_file(pass, *render_wait_len_ptr, sync_file_fds[i]);
+		if (sem == VK_NULL_HANDLE) {
+			close(sync_file_fds[i]);
+			continue;
+		}
+
+		render_wait[*render_wait_len_ptr] = (VkSemaphoreSubmitInfoKHR){
+			.sType = VK_STRUCTURE_TYPE_SEMAPHORE_SUBMIT_INFO_KHR,
+			.semaphore = sem,
+			.stageMask = VK_PIPELINE_STAGE_2_ALL_COMMANDS_BIT_KHR,
+		};
+
+		(*render_wait_len_ptr)++;
+	}
+
+	return true;
+}
+
 static bool unwrap_color_transform(struct wlr_color_transform *transform,
 		float matrix[static 9], enum wlr_color_transfer_function *tf) {
 	if (transform == NULL) {
@@ -308,7 +342,7 @@ static bool render_pass_submit(struct wlr_render_pass *wlr_pass) {
 	vkCmdEndRenderPass(render_cb->vk);
 
 	size_t pass_textures_len = pass->textures.size / sizeof(struct wlr_vk_render_pass_texture);
-	size_t render_wait_cap = pass_textures_len * WLR_DMABUF_MAX_PLANES;
+	size_t render_wait_cap = (1 + pass_textures_len) * WLR_DMABUF_MAX_PLANES;
 	render_wait = calloc(render_wait_cap, sizeof(*render_wait));
 	if (render_wait == NULL) {
 		wlr_log_errno(WLR_ERROR, "Allocation failed");
@@ -413,6 +447,10 @@ static bool render_pass_submit(struct wlr_render_pass *wlr_pass) {
 		}
 	}
 
+	if (!render_pass_wait_render_buffer(pass, render_wait, &render_wait_len)) {
+		wlr_log(WLR_ERROR, "Failed to wait for render buffer DMA-BUF fence");
+	}
+
 	// also add acquire/release barriers for the current render buffer
 	VkImageLayout src_layout = VK_IMAGE_LAYOUT_GENERAL;
 	if (!pass->render_buffer_out->transitioned) {
diff --git a/render/vulkan/renderer.c b/render/vulkan/renderer.c
index feafcbc34..da17a4703 100644
--- a/render/vulkan/renderer.c
+++ b/render/vulkan/renderer.c
@@ -1016,6 +1016,12 @@ bool vulkan_sync_foreign_texture_acquire(struct wlr_vk_texture *texture,
 	return buffer_export_sync_file(texture->renderer, texture->buffer, DMA_BUF_SYNC_READ, sync_file_fds);
 }
 
+bool vulkan_sync_render_buffer_acquire(struct wlr_vk_render_buffer *render_buffer,
+		int sync_file_fds[static WLR_DMABUF_MAX_PLANES]) {
+	return buffer_export_sync_file(render_buffer->renderer, render_buffer->wlr_buffer,
+		DMA_BUF_SYNC_WRITE, sync_file_fds);
+}
+
 static bool buffer_import_sync_file(struct wlr_buffer *buffer, uint32_t flags, int sync_file_fd) {
 	struct wlr_dmabuf_attributes dmabuf = {0};
 	if (!wlr_buffer_get_dmabuf(buffer, &dmabuf)) {