Add pty09 test

Verify that slave pseudo-terminal can be opened multiple times
in parallel.

Reviewed-by: Cyril Hrubis <[email protected]>
Signed-off-by: Andrea Cervesato <[email protected]>

runtest/pty

@@ -7,6 +7,7 @@ pty05 pty05
 pty06 pty06
 pty07 pty07
 pty08 pty08
+pty09 pty09
 ptem01 ptem01
 ptem02 ptem02
 ptem03 ptem03

testcases/kernel/pty/.gitignore

@@ -13,3 +13,4 @@
 /pty06
 /pty07
 /pty08
+/pty09

testcases/kernel/pty/pty09.c

@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) International Business Machines  Corp., 2002
+ * Copyright (C) 2024 SUSE LLC Andrea Cervesato <[email protected]>
+ */
+
+/*\
+ * [Description]
+ *
+ * Verify that slave pseudo-terminal can be opened multiple times in parallel.
+ */
+
+#define _GNU_SOURCE
+
+#include "common.h"
+
+static int masterfd = -1;
+
+static unsigned int count_avail_pid(void)
+{
+	DIR *dir;
+	struct dirent *ent;
+	struct rlimit limit;
+	unsigned int count = 0;
+	unsigned int max_pid_num;
+
+	SAFE_GETRLIMIT(RLIMIT_NOFILE, &limit);
+
+	dir = SAFE_OPENDIR("/proc/self/fd");
+	while ((ent = SAFE_READDIR(dir)))
+		count++;
+
+	SAFE_CLOSEDIR(dir);
+
+	max_pid_num = limit.rlim_cur - count;
+
+	tst_res(TINFO, "Available number of pids: %u", max_pid_num);
+
+	return max_pid_num;
+}
+
+static void run(void)
+{
+	unsigned int max_pid_num;
+
+	max_pid_num = count_avail_pid();
+
+	int slavefd[max_pid_num];
+
+	for (uint32_t i = 0; i < max_pid_num; i++)
+		slavefd[i] = open_slave(masterfd);
+
+	tst_res(TPASS, "pty has been opened %d times", max_pid_num);
+
+	for (uint32_t i = 0; i < max_pid_num; i++)
+		SAFE_CLOSE(slavefd[i]);
+}
+
+static void setup(void)
+{
+	masterfd = open_master();
+}
+
+static void cleanup(void)
+{
+	if (masterfd != -1)
+		SAFE_CLOSE(masterfd);
+}
+
+static struct tst_test test = {
+	.test_all = run,
+	.setup = setup,
+	.cleanup = cleanup,
+};