[PATCH wayland 1/2] shm: Split pool reference counting into external and internal references

[Derek Foreman]

This is a preliminary step towards deferring shm resize operations until
after the compositor has released all external references on a pool.

Signed-off-by: Derek Foreman <der...@osg.samsung.com>
---
 src/wayland-shm.c | 31 +++++++++++++++++++------------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/src/wayland-shm.c b/src/wayland-shm.c
index a4343a4..6fbf34b 100644
--- a/src/wayland-shm.c
+++ b/src/wayland-shm.c
@@ -52,7 +52,8 @@ static struct sigaction wl_shm_old_sigbus_action;
 
 struct wl_shm_pool {
        struct wl_resource *resource;
-       int refcount;
+       int internal_refcount;
+       int external_refcount;
        char *data;
        int32_t size;
 };
@@ -73,10 +74,14 @@ struct wl_shm_sigbus_data {
 };
 
 static void
-shm_pool_unref(struct wl_shm_pool *pool)
+shm_pool_unref(struct wl_shm_pool *pool, bool external)
 {
-       pool->refcount--;
-       if (pool->refcount)
+       if (external)
+               pool->external_refcount--;
+       else
+               pool->internal_refcount--;
+
+       if (pool->internal_refcount + pool->external_refcount)
                return;
 
        munmap(pool->data, pool->size);
@@ -89,7 +94,7 @@ destroy_buffer(struct wl_resource *resource)
        struct wl_shm_buffer *buffer = wl_resource_get_user_data(resource);
 
        if (buffer->pool)
-               shm_pool_unref(buffer->pool);
+               shm_pool_unref(buffer->pool, false);
        free(buffer);
 }
 
@@ -162,13 +167,13 @@ shm_pool_create_buffer(struct wl_client *client, struct 
wl_resource *resource,
        buffer->stride = stride;
        buffer->offset = offset;
        buffer->pool = pool;
-       pool->refcount++;
+       pool->internal_refcount++;
 
        buffer->resource =
                wl_resource_create(client, &wl_buffer_interface, 1, id);
        if (buffer->resource == NULL) {
                wl_client_post_no_memory(client);
-               shm_pool_unref(pool);
+               shm_pool_unref(pool, false);
                free(buffer);
                return;
        }
@@ -183,7 +188,7 @@ destroy_pool(struct wl_resource *resource)
 {
        struct wl_shm_pool *pool = wl_resource_get_user_data(resource);
 
-       shm_pool_unref(pool);
+       shm_pool_unref(pool, false);
 }
 
 static void
@@ -243,7 +248,8 @@ shm_create_pool(struct wl_client *client, struct 
wl_resource *resource,
                goto err_free;
        }
 
-       pool->refcount = 1;
+       pool->internal_refcount = 1;
+       pool->external_refcount = 0;
        pool->size = size;
        pool->data = mmap(NULL, size,
                          PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
@@ -396,9 +402,10 @@ wl_shm_buffer_get_height(struct wl_shm_buffer *buffer)
 WL_EXPORT struct wl_shm_pool *
 wl_shm_buffer_ref_pool(struct wl_shm_buffer *buffer)
 {
-       assert(buffer->pool->refcount);
+       assert(buffer->pool->internal_refcount +
+              buffer->pool->external_refcount);
 
-       buffer->pool->refcount++;
+       buffer->pool->external_refcount++;
        return buffer->pool;
 }
 
@@ -418,7 +425,7 @@ wl_shm_buffer_ref_pool(struct wl_shm_buffer *buffer)
 WL_EXPORT void
 wl_shm_pool_unref(struct wl_shm_pool *pool)
 {
-       shm_pool_unref(pool);
+       shm_pool_unref(pool, true);
 }
 
 static void
-- 
2.7.0

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