[tracker] libtracker-data: Use internal mutex in TrackerDBInterfaceSqlite

[Carlos Garnacho <carlosg src gnome org>]

commit f185c630e7a0dd9208f23df248b331e899315224
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sat Nov 5 19:37:22 2016 +0100

    libtracker-data: Use internal mutex in TrackerDBInterfaceSqlite
    
    There is no reason to use a global mutex for multiple TrackerDBInterfaces,
    the threading restriction in sqlite is "no multiple threads using the same
    sqlite3* at the same time" (being cursor included "using" there). This
    means we must restrict simultaneous threaded access to a single
    TrackerDBInterface, but multiple threads are free to use a
    TrackerDBInterface each without further interference.
    
    So, use a per-TrackerDBInterface mutex instead of a global one, if multiple
    cursors are created on the same interface, they'll backreference to it, so
    will be blocking on the same mutex.

 src/libtracker-data/tracker-db-interface-sqlite.c |  110 ++++++++++----------
 1 files changed, 55 insertions(+), 55 deletions(-)
---
diff --git a/src/libtracker-data/tracker-db-interface-sqlite.c 
b/src/libtracker-data/tracker-db-interface-sqlite.c
index 4d72e1a..2ceea27 100644
--- a/src/libtracker-data/tracker-db-interface-sqlite.c
+++ b/src/libtracker-data/tracker-db-interface-sqlite.c
@@ -94,6 +94,10 @@ struct TrackerDBInterface {
        gchar *busy_status;
 
        gchar *fts_properties;
+
+       /* Used if TRACKER_DB_MANAGER_ENABLE_MUTEXES is set */
+       GMutex mutex;
+       guint use_mutex;
 };
 
 struct TrackerDBInterfaceClass {
@@ -109,10 +113,6 @@ struct TrackerDBCursor {
        gint n_types;
        gchar **variable_names;
        gint n_variable_names;
-
-       /* used for direct access as libtracker-sparql is thread-safe and
-          uses a single shared connection with SQLite mutex disabled */
-       gboolean threadsafe;
 };
 
 struct TrackerDBCursorClass {
@@ -1433,6 +1433,20 @@ initialize_functions (TrackerDBInterface *db_interface)
        }
 }
 
+static inline void
+tracker_db_interface_lock (TrackerDBInterface *iface)
+{
+       if (iface->use_mutex)
+               g_mutex_lock (&iface->mutex);
+}
+
+static inline void
+tracker_db_interface_unlock (TrackerDBInterface *iface)
+{
+       if (iface->use_mutex)
+               g_mutex_unlock (&iface->mutex);
+}
+
 static void
 open_database (TrackerDBInterface  *db_interface,
                GError             **error)
@@ -1912,6 +1926,8 @@ static void
 tracker_db_interface_init (TrackerDBInterface *db_interface)
 {
        db_interface->ro = FALSE;
+       db_interface->use_mutex = (tracker_db_manager_get_flags (NULL, NULL) &
+                                  TRACKER_DB_MANAGER_ENABLE_MUTEXES) != 0;
 
        prepare_database (db_interface);
 }
@@ -2384,18 +2400,14 @@ tracker_db_cursor_close (TrackerDBCursor *cursor)
        iface = cursor->ref_stmt->db_interface;
        g_atomic_int_add (&iface->n_active_cursors, -1);
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_lock ();
-       }
+       tracker_db_interface_lock (iface);
 
        cursor->ref_stmt->stmt_is_used = FALSE;
        tracker_db_statement_sqlite_reset (cursor->ref_stmt);
        g_object_unref (cursor->ref_stmt);
        cursor->ref_stmt = NULL;
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_unlock ();
-       }
+       tracker_db_interface_unlock (iface);
 }
 
 static void
@@ -2518,9 +2530,6 @@ tracker_db_cursor_sqlite_new (TrackerDBStatement  *ref_stmt,
 
        cursor->finished = FALSE;
 
-       cursor->threadsafe = (tracker_db_manager_get_flags (NULL, NULL) &
-                             TRACKER_DB_MANAGER_ENABLE_MUTEXES) != 0;
-
        cursor->stmt = ref_stmt->stmt;
        ref_stmt->stmt_is_used = TRUE;
        cursor->ref_stmt = g_object_ref (ref_stmt);
@@ -2598,18 +2607,18 @@ tracker_db_statement_bind_text (TrackerDBStatement *stmt,
 void
 tracker_db_cursor_rewind (TrackerDBCursor *cursor)
 {
+       TrackerDBInterface *iface;
+
        g_return_if_fail (TRACKER_IS_DB_CURSOR (cursor));
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_lock ();
-       }
+       iface = cursor->ref_stmt->db_interface;
+
+       tracker_db_interface_lock (iface);
 
        sqlite3_reset (cursor->stmt);
        cursor->finished = FALSE;
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_unlock ();
-       }
+       tracker_db_interface_unlock (iface);
 }
 
 gboolean
@@ -2636,9 +2645,7 @@ db_cursor_iter_next (TrackerDBCursor *cursor,
        if (!cursor->finished) {
                guint result;
 
-               if (cursor->threadsafe) {
-                       tracker_db_manager_lock ();
-               }
+               tracker_db_interface_lock (iface);
 
                if (g_cancellable_is_cancelled (cancellable)) {
                        result = SQLITE_INTERRUPT;
@@ -2664,9 +2671,7 @@ db_cursor_iter_next (TrackerDBCursor *cursor,
 
                cursor->finished = (result != SQLITE_ROW);
 
-               if (cursor->threadsafe) {
-                       tracker_db_manager_unlock ();
-               }
+               tracker_db_interface_unlock (iface);
        }
 
        return (!cursor->finished);
@@ -2713,17 +2718,16 @@ gint64
 tracker_db_cursor_get_int (TrackerDBCursor *cursor,
                            guint            column)
 {
+       TrackerDBInterface *iface;
        gint64 result;
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_lock ();
-       }
+       iface = cursor->ref_stmt->db_interface;
+
+       tracker_db_interface_lock (iface);
 
        result = (gint64) sqlite3_column_int64 (cursor->stmt, column);
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_unlock ();
-       }
+       tracker_db_interface_unlock (iface);
 
        return result;
 }
@@ -2732,17 +2736,16 @@ gdouble
 tracker_db_cursor_get_double (TrackerDBCursor *cursor,
                               guint            column)
 {
+       TrackerDBInterface *iface;
        gdouble result;
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_lock ();
-       }
+       iface = cursor->ref_stmt->db_interface;
+
+       tracker_db_interface_lock (iface);
 
        result = (gdouble) sqlite3_column_double (cursor->stmt, column);
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_unlock ();
-       }
+       tracker_db_interface_unlock (iface);
 
        return result;
 }
@@ -2759,20 +2762,19 @@ TrackerSparqlValueType
 tracker_db_cursor_get_value_type (TrackerDBCursor *cursor,
                                   guint            column)
 {
+       TrackerDBInterface *iface;
        gint column_type;
        gint n_columns = sqlite3_column_count (cursor->stmt);
 
        g_return_val_if_fail (column < n_columns, TRACKER_SPARQL_VALUE_TYPE_UNBOUND);
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_lock ();
-       }
+       iface = cursor->ref_stmt->db_interface;
+
+       tracker_db_interface_lock (iface);
 
        column_type = sqlite3_column_type (cursor->stmt, column);
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_unlock ();
-       }
+       tracker_db_interface_unlock (iface);
 
        if (column_type == SQLITE_NULL) {
                return TRACKER_SPARQL_VALUE_TYPE_UNBOUND;
@@ -2800,11 +2802,12 @@ const gchar*
 tracker_db_cursor_get_variable_name (TrackerDBCursor *cursor,
                                      guint            column)
 {
+       TrackerDBInterface *iface;
        const gchar *result;
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_lock ();
-       }
+       iface = cursor->ref_stmt->db_interface;
+
+       tracker_db_interface_lock (iface);
 
        if (column < cursor->n_variable_names) {
                result = cursor->variable_names[column];
@@ -2812,9 +2815,7 @@ tracker_db_cursor_get_variable_name (TrackerDBCursor *cursor,
                result = sqlite3_column_name (cursor->stmt, column);
        }
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_unlock ();
-       }
+       tracker_db_interface_unlock (iface);
 
        return result;
 }
@@ -2824,11 +2825,12 @@ tracker_db_cursor_get_string (TrackerDBCursor *cursor,
                               guint            column,
                               glong           *length)
 {
+       TrackerDBInterface *iface;
        const gchar *result;
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_lock ();
-       }
+       iface = cursor->ref_stmt->db_interface;
+
+       tracker_db_interface_lock (iface);
 
        if (length) {
                sqlite3_value *val = sqlite3_column_value (cursor->stmt, column);
@@ -2839,9 +2841,7 @@ tracker_db_cursor_get_string (TrackerDBCursor *cursor,
                result = (const gchar *) sqlite3_column_text (cursor->stmt, column);
        }
 
-       if (cursor->threadsafe) {
-               tracker_db_manager_unlock ();
-       }
+       tracker_db_interface_unlock (iface);
 
        return result;
 }