Demonstrate signal safety of recursive mutexes

test/posix/exit_async_signal_safety_test.c

@@ -0,0 +1,30 @@
+#include <pthread.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+atomic_bool ready;
+
+void* work(void* arg) {
+  pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, 0);
+  ready = true;
+  pthread_exit(0);
+}
+
+int main() {
+
+  for (int i = 0; i < 1000; ++i) {
+    pthread_t th;
+    if (pthread_create(&th, 0, work, 0))
+      _Exit(1);
+    for (;;)
+      if (ready)
+        break;
+    pthread_cancel(th);
+    if (pthread_join(th, 0))
+      _Exit(3);
+  }
+
+  while (!pthread_orphan_np())
+    pthread_decimate_np();
+}