// ToDo: for SMP, we should probably acquire *all* the capabilities
cap = rts_lock();
+ // no funny business: hold locks while we fork, otherwise if some
+ // other thread is holding a lock when the fork happens, the data
+ // structure protected by the lock will forever be in an
+ // inconsistent state in the child. See also #1391.
+ ACQUIRE_LOCK(&sched_mutex);
+ ACQUIRE_LOCK(&cap->lock);
+
pid = fork();
if (pid) { // parent
+ RELEASE_LOCK(&sched_mutex);
+ RELEASE_LOCK(&cap->lock);
+
// just return the pid
rts_unlock(cap);
return pid;
} else { // child
+#if defined(THREADED_RTS)
+ initMutex(&sched_mutex);
+ initMutex(&cap->lock);
+#endif
+
// Now, all OS threads except the thread that forked are
// stopped. We need to stop all Haskell threads, including
// those involved in foreign calls. Also we need to delete