Allow both recursive and non-recursive mutexes to be supplied

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=43744
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Thiago Macieira <thiago@kde.org>

2 files changed, 17 insertions, 25 deletions

diff --git a/dbus/dbus-threads.c b/dbus/dbus-threads.c
index eff30542..81308477 100644
--- a/dbus/dbus-threads.c
+++ b/dbus/dbus-threads.c
@@ -734,13 +734,6 @@ dbus_threads_init (const DBusThreadFunctions *functions)
                               "functions sets should be passed into "
                               "dbus_threads_init. Neither sets were passed.");
 
-  if (mutex_set && recursive_mutex_set)
-    _dbus_assert_not_reached ("Either the nonrecusrive or recursive mutex " 
-                              "functions sets should be passed into "
-                              "dbus_threads_init. Both sets were passed. "
-                              "You most likely just want to set the recursive "
-                              "mutex functions to avoid deadlocks in D-Bus.");
-                          
   /* Check that all bits in the mask actually are valid mask bits.
    * ensures people won't write code that breaks when we add
    * new bits.
@@ -770,15 +763,23 @@ dbus_threads_init (const DBusThreadFunctions *functions)
  
   if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_NEW_MASK)
     thread_functions.recursive_mutex_new = functions->recursive_mutex_new;
-  
+  else
+    thread_functions.recursive_mutex_new = NULL;
+
   if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_FREE_MASK)
     thread_functions.recursive_mutex_free = functions->recursive_mutex_free;
-  
+  else
+    thread_functions.recursive_mutex_free = NULL;
+
   if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_LOCK_MASK)
     thread_functions.recursive_mutex_lock = functions->recursive_mutex_lock;
+  else
+    thread_functions.recursive_mutex_lock = NULL;
 
   if (functions->mask & DBUS_THREAD_FUNCTIONS_RECURSIVE_MUTEX_UNLOCK_MASK)
     thread_functions.recursive_mutex_unlock = functions->recursive_mutex_unlock;
+  else
+    thread_functions.recursive_mutex_unlock = NULL;
 
   thread_functions.mask = functions->mask;
 
diff --git a/dbus/dbus-threads.h b/dbus/dbus-threads.h
index ba07ca57..6d28a0b6 100644
--- a/dbus/dbus-threads.h
+++ b/dbus/dbus-threads.h
@@ -139,24 +139,15 @@ typedef enum
 
 /**
  * Functions that must be implemented to make the D-Bus library
- * thread-aware. The recursive mutex functions should be specified
- * rather than the old, deprecated nonrecursive ones.
+ * thread-aware.
  *
- * The condition variable functions have to work with recursive
- * mutexes if you provide those, or with nonrecursive mutexes if you
- * provide those.
+ * If you supply both recursive and non-recursive mutexes,
+ * libdbus will use the non-recursive version for condition variables,
+ * and the recursive version in other contexts.
  *
- * If implementing threads using pthreads, be aware that
- * PTHREAD_MUTEX_RECURSIVE is broken in combination with condition
- * variables. libdbus relies on the Java-style behavior that when
- * waiting on a condition, the recursion count is saved and restored,
- * and the mutex is completely unlocked, not just decremented one
- * level of recursion.
- *
- * Thus with pthreads you probably have to roll your own emulated
- * recursive mutexes, you can't use PTHREAD_MUTEX_RECURSIVE. This is
- * what dbus_threads_init_default() does on platforms that use
- * pthreads.
+ * The condition variable functions have to work with nonrecursive
+ * mutexes if you provide those, or with recursive mutexes if you
+ * don't.
  */
 typedef struct
 {