[PATCH wayland] shm: Add wl_shm_buffer get/put functions

[Derek Foreman]

Sometimes the compositor wants to make sure a shm pool doesn't disappear
out from under it.

For example, in Enlightenment, rendering happens in a separate thread
while the main thread can still dispatch events.  If a client is destroyed
during rendering, all its resources are cleaned up and its shm pools are
unmapped.  This causes the rendering thread to segfault.

This patch adds a way for the compositor to increment the refcount of the
shm pool so it can't disappear, and decrement it when it's finished.

Signed-off-by: Derek Foreman <derekf at osg.samsung.com>
---
 src/wayland-server-core.h |  7 +++++++
 src/wayland-shm.c         | 15 +++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/src/wayland-server-core.h b/src/wayland-server-core.h
index e605432..a4a04fc 100644
--- a/src/wayland-server-core.h
+++ b/src/wayland-server-core.h
@@ -362,6 +362,7 @@ wl_resource_get_destroy_listener(struct wl_resource *resource,
 	     resource = tmp,							\
 	     tmp = wl_resource_from_link(wl_resource_get_link(resource)->next))
 
+struct wl_shm_pool;
 struct wl_shm_buffer;
 
 void
@@ -388,6 +389,12 @@ wl_shm_buffer_get_width(struct wl_shm_buffer *buffer);
 int32_t
 wl_shm_buffer_get_height(struct wl_shm_buffer *buffer);
 
+struct wl_shm_pool *
+wl_shm_buffer_get_pool(struct wl_shm_buffer *buffer);
+
+void
+wl_shm_buffer_put_pool(struct wl_shm_pool *pool);
+
 int
 wl_display_init_shm(struct wl_display *display);
 
diff --git a/src/wayland-shm.c b/src/wayland-shm.c
index 5c419fa..48b5140 100644
--- a/src/wayland-shm.c
+++ b/src/wayland-shm.c
@@ -412,6 +412,21 @@ wl_shm_buffer_get_height(struct wl_shm_buffer *buffer)
 	return buffer->height;
 }
 
+WL_EXPORT struct wl_shm_pool *
+wl_shm_buffer_get_pool(struct wl_shm_buffer *buffer)
+{
+	assert(buffer->pool->refcount);
+
+	buffer->pool->refcount++;
+	return buffer->pool;
+}
+
+WL_EXPORT void
+wl_shm_buffer_put_pool(struct wl_shm_pool *pool)
+{
+	shm_pool_unref(pool);
+}
+
 static void
 reraise_sigbus(void)
 {
-- 
2.1.4