Add a statically-initialized implementation of _dbus_lock() on glibc systems

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=54972
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Reviewed-by: Anas Nashif <anas.nashif@intel.com>

diff --git a/dbus/dbus-sysdeps-pthread.c b/dbus/dbus-sysdeps-pthread.c
index 1300ec3..2180c37 100644 (file)
--- a/dbus/dbus-sysdeps-pthread.c
+++ b/dbus/dbus-sysdeps-pthread.c
@@ -300,3 +300,50 @@ _dbus_threads_unlock_platform_specific (void)
 {
   pthread_mutex_unlock (&init_mutex);
 }
+
+#ifdef DBUS_HAVE_STATIC_RECURSIVE_MUTEXES
+
+static pthread_mutex_t global_locks[] = {
+    /* 0-4 */
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    /* 5-9 */
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    /* 10-11 */
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP,
+    PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
+};
+
+_DBUS_STATIC_ASSERT (_DBUS_N_ELEMENTS (global_locks) == _DBUS_N_GLOBAL_LOCKS);
+
+dbus_bool_t
+_dbus_lock (DBusGlobalLock lock)
+{
+  /* No initialization is needed. */
+  _dbus_assert (lock >= 0);
+  _dbus_assert (lock < _DBUS_N_GLOBAL_LOCKS);
+
+  PTHREAD_CHECK ("pthread_mutex_lock",
+      pthread_mutex_lock (&(global_locks[lock])));
+  return TRUE;
+}
+
+void
+_dbus_unlock (DBusGlobalLock lock)
+{
+  /* No initialization is needed. */
+  _dbus_assert (lock >= 0);
+  _dbus_assert (lock < _DBUS_N_GLOBAL_LOCKS);
+
+  PTHREAD_CHECK ("pthread_mutex_unlock",
+      pthread_mutex_unlock (&(global_locks[lock])));
+}
+
+#endif

diff --git a/dbus/dbus-threads-internal.h b/dbus/dbus-threads-internal.h
index 64e8bac..228a8c0 100644 (file)
--- a/dbus/dbus-threads-internal.h
+++ b/dbus/dbus-threads-internal.h
@@ -32,6 +32,12 @@
  * @{
  */
 
+/* glibc can implement global locks without needing an initialization step,
+ * which improves our thread-safety-by-default further. */
+#if defined(__GLIBC__) && defined(PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP)
+#   define DBUS_HAVE_STATIC_RECURSIVE_MUTEXES 1
+#endif
+
 /**
  * A mutex which is recursive if possible, else non-recursive.
  * This is typically recursive, but that cannot be relied upon.

diff --git a/dbus/dbus-threads.c b/dbus/dbus-threads.c
index 29462eb..1781bda 100644 (file)
--- a/dbus/dbus-threads.c
+++ b/dbus/dbus-threads.c
@@ -283,6 +283,18 @@ _dbus_condvar_wake_one (DBusCondVar *cond)
   _dbus_platform_condvar_wake_one (cond);
 }
 
+#ifdef DBUS_HAVE_STATIC_RECURSIVE_MUTEXES
+
+static dbus_bool_t
+init_global_locks (void)
+{
+  return TRUE;
+}
+
+/* implementations in dbus-sysdeps-pthread.c */
+
+#else /* !defined(DBUS_HAVE_STATIC_RECURSIVE_MUTEXES) */
+
 static DBusRMutex *global_locks[_DBUS_N_GLOBAL_LOCKS] = { NULL };
 
 static void
@@ -356,6 +368,8 @@ _dbus_unlock (DBusGlobalLock lock)
   _dbus_platform_rmutex_unlock (global_locks[lock]);
 }
 
+#endif /* !defined(DBUS_HAVE_STATIC_RECURSIVE_MUTEXES) */
+
 /** @} */ /* end of internals */
 
 /**