1 files changed, 37 insertions, 0 deletions
diff --git a/lib/libc/thread/thrd_join.c b/lib/libc/thread/thrd_join.c
new file mode 100644
index 00000000..7ec38c4a
--- /dev/null
+++ b/lib/libc/thread/thrd_join.c
@@ -0,0 +1,37 @@
+#include <__thread.h>
+#include <libc/futex.h>
+#include <stdatomic.h>
+#include <sys/mman.h>
+#include <threads.h>
+
+int thrd_join(thrd_t thr, int *res)
+{
+	struct __thread_self *tcb = (struct __thread_self *)thr;
+	if (tcb == NULL)
+		return thrd_error;
+
+	int state = atomic_load_explicit(&tcb->state, memory_order_seq_cst);
+	if (state == THREAD_STATE_DETACHED)
+		return thrd_error; // Cannot join a detached thread
+
+	while (atomic_load_explicit(&tcb->state, memory_order_seq_cst) != THREAD_STATE_EXITED) {
+		int cur = atomic_load_explicit(&tcb->state, memory_order_seq_cst);
+		int r = __futex_wait((volatile int *)&tcb->state, cur);
+		if (r < 0)
+			return thrd_error;
+	}
+
+	if (res) {
+		*res = tcb->res;
+	}
+
+	atomic_store_explicit(&tcb->state, THREAD_STATE_JOINABLE, memory_order_seq_cst);
+	__futex_wake((volatile int *)&tcb->state, 1);
+
+	if (tcb->map_base == NULL || tcb->map_size == 0)
+		return thrd_error;
+
+	munmap(tcb->map_base, tcb->map_size);
+
+	return thrd_success;
+}