process-shared barrier support, based on discussion with bdonlan

this implementation is rather heavy-weight, but it's the first
solution i've found that's actually correct. all waiters actually wait
twice at the barrier so that they can synchronize exit, and they hold
a "vm lock" that prevents changes to virtual memory mappings (and
blocks pthread_barrier_destroy) until all waiters are finished
inspecting the barrier.

thus, it is safe for any thread to destroy and/or unmap the barrier's
memory as soon as pthread_barrier_wait returns, without further
synchronization.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/thread/pthread_barrierattr_setpshared.c b/src/thread/pthread_barrierattr_setpshared.c
index d6c7f9a3..1edc95dc 100644
--- a/src/thread/pthread_barrierattr_setpshared.c
+++ b/src/thread/pthread_barrierattr_setpshared.c
@@ -2,6 +2,6 @@
 
 int pthread_barrierattr_setpshared(pthread_barrierattr_t *a, int pshared)
 {
-	*a = !!pshared;
+	*a = pshared ? INT_MIN : 0;
 	return 0;
 }