Avoid race-condition when initializing global locks

Previously, we did stuff like
   if (!lock)
      EVTHREAD_ALLOC_LOCK(lock,0);
for the evsig base global lock, the arc4random lock, and the debug_map
lock.  But that's potentially racy!  Instead, we move the
responisiblity for global lock initialization to the functions where
we set up the lock callbacks.

(Rationale: We already require that you set up the locking callbacks
before you create any event_base, and that you do so exatly once.)

1 files changed, 18 insertions, 0 deletions

diff --git a/evthread-internal.h b/evthread-internal.h
index 9317fdf1..fbb1c0d4 100644
--- a/evthread-internal.h
+++ b/evthread-internal.h
@@ -345,6 +345,24 @@ EVLOCK_TRY_LOCK(void *lock)
 
 int _evthread_is_debug_lock_held(void *lock);
 void *_evthread_debug_get_real_lock(void *lock);
+
+void *evthread_setup_global_lock_(void *lock_, unsigned locktype,
+    int enable_locks);
+
+#define EVTHREAD_SETUP_GLOBAL_LOCK(lockvar, locktype)			\
+	do {								\
+		lockvar = evthread_setup_global_lock_(lockvar,		\
+		    (locktype), enable_locks);				\
+		if (!lockvar) {						\
+			event_warn("Couldn't allocate %s", #lockvar);	\
+			return -1;					\
+		}							\
+	} while (0);
+
+int event_global_setup_locks_(const int enable_locks);
+int evsig_global_setup_locks_(const int enable_locks);
+int evutil_secure_rng_global_setup_locks_(const int enable_locks);
+
 #endif
 
 #ifdef __cplusplus