[gnome-software/gnome-3-22] snap: Protect store cache with a lock

[Robert Ancell <rancell src gnome org>]

commit 0f50f99b705e71b222d403a12f852bd91e7b5fd5
Author: Robert Ancell <robert ancell canonical com>
Date:   Fri Oct 27 10:28:09 2017 +1300

    snap: Protect store cache with a lock
    
    The store cache is likely to be accessed by multiple threads on startup as the
    popular / featured and installed snaps are requested in parallel.

 src/plugins/gs-plugin-snap.c |   36 +++++++++++++++++++++++++++---------
 1 files changed, 27 insertions(+), 9 deletions(-)
---
diff --git a/src/plugins/gs-plugin-snap.c b/src/plugins/gs-plugin-snap.c
index 9277443..32a440e 100644
--- a/src/plugins/gs-plugin-snap.c
+++ b/src/plugins/gs-plugin-snap.c
@@ -30,6 +30,8 @@
 struct GsPluginData {
        gboolean         system_is_confined;
        GsAuth          *auth;
+
+       GMutex           store_snaps_lock;
        GHashTable      *store_snaps;
 };
 
@@ -46,6 +48,7 @@ gs_plugin_initialize (GsPlugin *plugin)
                gs_plugin_set_enabled (plugin, FALSE);
        }
 
+       g_mutex_init (&priv->store_snaps_lock);
        priv->store_snaps = g_hash_table_new_full (g_str_hash, g_str_equal,
                                                   g_free, (GDestroyNotify) json_object_unref);
 
@@ -141,25 +144,40 @@ gs_plugin_snap_set_app_pixbuf_from_data (GsApp *app, const gchar *buf, gsize cou
        return TRUE;
 }
 
+static JsonObject *
+store_snap_cache_lookup (GsPlugin *plugin, const gchar *name)
+{
+       GsPluginData *priv = gs_plugin_get_data (plugin);
+       g_autoptr(GMutexLocker) locker = g_mutex_locker_new (&priv->store_snaps_lock);
+       return g_hash_table_lookup (priv->store_snaps, name);
+}
+
+static void
+store_snap_cache_update (GsPlugin *plugin, JsonArray *snaps)
+{
+       GsPluginData *priv = gs_plugin_get_data (plugin);
+       g_autoptr(GMutexLocker) locker = g_mutex_locker_new (&priv->store_snaps_lock);
+       guint i;
+
+       for (i = 0; i < json_array_get_length (snaps); i++) {
+               JsonObject *snap = json_array_get_object_element (snaps, i);
+               g_hash_table_insert (priv->store_snaps, g_strdup (json_object_get_string_member (snap, 
"name")), json_object_ref (snap));
+       }
+}
+
 static JsonArray *
 find_snaps (GsPlugin *plugin, const gchar *section, gboolean match_name, const gchar *query, GCancellable 
*cancellable, GError **error)
 {
-       GsPluginData *priv = gs_plugin_get_data (plugin);
        g_autofree gchar *macaroon = NULL;
        g_auto(GStrv) discharges = NULL;
        g_autoptr(JsonArray) snaps = NULL;
-       guint i;
 
        get_macaroon (plugin, &macaroon, &discharges);
        snaps = gs_snapd_find (macaroon, discharges, section, match_name, query, cancellable, error);
        if (snaps == NULL)
                return NULL;
 
-       /* cache results */
-       for (i = 0; i < json_array_get_length (snaps); i++) {
-               JsonObject *snap = json_array_get_object_element (snaps, i);
-               g_hash_table_insert (priv->store_snaps, g_strdup (json_object_get_string_member (snap, 
"name")), json_object_ref (snap));
-       }
+       store_snap_cache_update (plugin, snaps);
 
        return g_steal_pointer (&snaps);
 }
@@ -212,6 +230,7 @@ gs_plugin_destroy (GsPlugin *plugin)
        GsPluginData *priv = gs_plugin_get_data (plugin);
        g_clear_object (&priv->auth);
        g_hash_table_unref (priv->store_snaps);
+       g_mutex_clear (&priv->store_snaps_lock);
 }
 
 gboolean
@@ -333,12 +352,11 @@ load_icon (GsPlugin *plugin, GsApp *app, const gchar *icon_url, GCancellable *ca
 static JsonObject *
 get_store_snap (GsPlugin *plugin, const gchar *name, GCancellable *cancellable, GError **error)
 {
-       GsPluginData *priv = gs_plugin_get_data (plugin);
        JsonObject *snap = NULL;
        g_autoptr(JsonArray) snaps = NULL;
 
        /* use cached version if available */
-       snap = g_hash_table_lookup (priv->store_snaps, name);
+       snap = store_snap_cache_lookup (plugin, name);
        if (snap != NULL)
                return json_object_ref (snap);