1 files changed, 23 insertions, 0 deletions
diff --git a/libc-top-half/musl/src/stdio/__lockfile.c b/libc-top-half/musl/src/stdio/__lockfile.c
new file mode 100644
index 0000000..0f60a14
--- /dev/null
+++ b/libc-top-half/musl/src/stdio/__lockfile.c
@@ -0,0 +1,23 @@
+#include "stdio_impl.h"
+#include "pthread_impl.h"
+
+int __lockfile(FILE *f)
+{
+	int owner = f->lock, tid = __pthread_self()->tid;
+	if ((owner & ~MAYBE_WAITERS) == tid)
+		return 0;
+	owner = a_cas(&f->lock, 0, tid);
+	if (!owner) return 1;
+	while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS))) {
+		if ((owner & MAYBE_WAITERS) ||
+		    a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner)
+			__futexwait(&f->lock, owner|MAYBE_WAITERS, 1);
+	}
+	return 1;
+}
+
+void __unlockfile(FILE *f)
+{
+	if (a_swap(&f->lock, 0) & MAYBE_WAITERS)
+		__wake(&f->lock, 1, 1);
+}