lib/libthr: add pthread_tryjoin(3) test

Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D54766

lib/libthr/tests/Makefile

@@ -36,6 +36,7 @@ NETBSD_ATF_TESTS_SH+=	resolv_test
 ATF_TESTS_C+=		atfork_test
 ATF_TESTS_C+=		umtx_op_test
 ATF_TESTS_C+=		pthread_sigqueue_test
+ATF_TESTS_C+=		pthread_tryjoin_test
 
 LIBADD+=		pthread
 LIBADD.fpu_test+=	m

lib/libthr/tests/pthread_tryjoin_test.c

@@ -0,0 +1,62 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright 2025 The FreeBSD Foundation
+ *
+ * This software was developed by Konstantin Belousov <kib@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ */
+
+#include <atf-c.h>
+#include <err.h>
+#include <errno.h>
+#include <pthread.h>
+#include <pthread_np.h>
+#include <stdatomic.h>
+#include <stdio.h>
+#include <unistd.h>
+
+static atomic_int finish;
+
+static void *
+thr_fun(void *arg)
+{
+	while (atomic_load_explicit(&finish, memory_order_relaxed) != 1)
+		sleep(1);
+	atomic_store_explicit(&finish, 2, memory_order_relaxed);
+	return (arg);
+}
+
+ATF_TC(pthread_tryjoin);
+ATF_TC_HEAD(pthread_tryjoin, tc)
+{
+	atf_tc_set_md_var(tc, "descr",
+	    "Checks pthread_tryjoin(3)");
+}
+
+ATF_TC_BODY(pthread_tryjoin, tc)
+{
+	pthread_t thr;
+	void *retval;
+	int error, x;
+
+	error = pthread_create(&thr, NULL, thr_fun, &x);
+	ATF_REQUIRE_EQ(error, 0);
+
+	error = pthread_tryjoin_np(thr, &retval);
+	ATF_REQUIRE_EQ(error, EBUSY);
+
+	atomic_store_explicit(&finish, 1, memory_order_relaxed);
+	while (atomic_load_explicit(&finish, memory_order_relaxed) != 2)
+		sleep(1);
+
+	error = pthread_tryjoin_np(thr, &retval);
+	ATF_REQUIRE_EQ(error, 0);
+	ATF_REQUIRE_EQ(retval, &x);
+}
+
+ATF_TP_ADD_TCS(tp)
+{
+	ATF_TP_ADD_TC(tp, pthread_tryjoin);
+	return (atf_no_error());
+}