From 361804c727ecd6b4ec5513097bd9135c1f04303e Mon Sep 17 00:00:00 2001
From: Simon Ser <contact@emersion.fr>
Date: Tue, 28 Nov 2023 17:14:48 +0100
Subject: [PATCH] buffer: allow concurrent data ptr accesses

---
 include/wlr/types/wlr_buffer.h |  7 ++++++-
 types/buffer/buffer.c          | 34 ++++++++++++++++++++++++++--------
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/include/wlr/types/wlr_buffer.h b/include/wlr/types/wlr_buffer.h
index de3aeec3d..82d3249b1 100644
--- a/include/wlr/types/wlr_buffer.h
+++ b/include/wlr/types/wlr_buffer.h
@@ -51,7 +51,12 @@ struct wlr_buffer {
 
 	bool dropped;
 	size_t n_locks;
-	bool accessing_data_ptr;
+
+	size_t n_data_ptr_accesses;
+	uint32_t data_ptr_access_flags; // bitfield of wlr_buffer_data_ptr_access_flag
+	void *data_ptr_access_data;
+	uint32_t data_ptr_access_format;
+	size_t data_ptr_access_stride;
 
 	struct {
 		struct wl_signal destroy;
diff --git a/types/buffer/buffer.c b/types/buffer/buffer.c
index a8e9c54d7..058cecfa3 100644
--- a/types/buffer/buffer.c
+++ b/types/buffer/buffer.c
@@ -26,7 +26,7 @@ static void buffer_consider_destroy(struct wlr_buffer *buffer) {
 		return;
 	}
 
-	assert(!buffer->accessing_data_ptr);
+	assert(buffer->n_data_ptr_accesses == 0);
 
 	wl_signal_emit_mutable(&buffer->events.destroy, NULL);
 	wlr_addon_set_finish(&buffer->addons);
@@ -74,21 +74,39 @@ bool wlr_buffer_get_dmabuf(struct wlr_buffer *buffer,
 
 bool wlr_buffer_begin_data_ptr_access(struct wlr_buffer *buffer, uint32_t flags,
 		void **data, uint32_t *format, size_t *stride) {
-	assert(!buffer->accessing_data_ptr);
 	if (!buffer->impl->begin_data_ptr_access) {
 		return false;
 	}
-	if (!buffer->impl->begin_data_ptr_access(buffer, flags, data, format, stride)) {
-		return false;
+	if (buffer->n_data_ptr_accesses == 0) {
+		if (!buffer->impl->begin_data_ptr_access(buffer, flags, data, format, stride)) {
+			return false;
+		}
+		buffer->data_ptr_access_flags = flags;
+		buffer->data_ptr_access_data = *data;
+		buffer->data_ptr_access_format = *format;
+		buffer->data_ptr_access_stride = *stride;
+	} else {
+		if (buffer->data_ptr_access_flags != flags) {
+			return false;
+		}
+		*data = buffer->data_ptr_access_data;
+		*format = buffer->data_ptr_access_format;
+		*stride = buffer->data_ptr_access_stride;
 	}
-	buffer->accessing_data_ptr = true;
+	buffer->n_data_ptr_accesses++;
 	return true;
 }
 
 void wlr_buffer_end_data_ptr_access(struct wlr_buffer *buffer) {
-	assert(buffer->accessing_data_ptr);
-	buffer->impl->end_data_ptr_access(buffer);
-	buffer->accessing_data_ptr = false;
+	assert(buffer->n_data_ptr_accesses > 0);
+	buffer->n_data_ptr_accesses--;
+	if (buffer->n_data_ptr_accesses == 0) {
+		buffer->impl->end_data_ptr_access(buffer);
+		buffer->data_ptr_access_flags = 0;
+		buffer->data_ptr_access_data = NULL;
+		buffer->data_ptr_access_format = 0;
+		buffer->data_ptr_access_stride = 0;
+	}
 }
 
 bool wlr_buffer_get_shm(struct wlr_buffer *buffer,