flock: Add test for verifying EINTR errno

Link: https://lore.kernel.org/ltp/[email protected]/
Reviewed-by: Petr Vorel <[email protected]>
Signed-off-by: Yang Xu <[email protected]>
Signed-off-by: Avinesh Kumar <[email protected]>

Author: Avinesh

runtest/syscalls

@@ -385,6 +385,7 @@ flock02 flock02
 flock03 flock03
 flock04 flock04
 flock06 flock06
+flock07 flock07
 
 fmtmsg01 fmtmsg01
 

testcases/kernel/syscalls/flock/.gitignore

@@ -3,3 +3,4 @@
 /flock03
 /flock04
 /flock06
+/flock07

testcases/kernel/syscalls/flock/flock07.c

@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2024 FUJITSU LIMITED. All Rights Reserved.
+ * Author: Yang Xu <[email protected]>
+ * Copyright (c) 2024 Linux Test Project
+ */
+
+/*\
+ * [Description]
+ *
+ * Verify that flock(2) fails with errno EINTR when waiting to acquire a lock,
+ * and the call is interrupted by a signal.
+ */
+
+#include <sys/file.h>
+#include "tst_test.h"
+
+#define TEMPFILE "test_eintr"
+
+static int fd1 = -1, fd2 = -1;
+
+static void handler(int sig)
+{
+	tst_res(TINFO, "Received signal: %s (%d)", tst_strsig(sig), sig);
+}
+
+static void setup(void)
+{
+	SAFE_TOUCH(TEMPFILE, 0777, NULL);
+	fd1 = SAFE_OPEN(TEMPFILE, O_RDWR);
+	fd2 = SAFE_OPEN(TEMPFILE, O_RDWR);
+}
+
+static void cleanup(void)
+{
+	if (fd1 >= 0)
+		SAFE_CLOSE(fd1);
+
+	if (fd2 >= 0)
+		SAFE_CLOSE(fd2);
+}
+
+static void child_do(int fd)
+{
+	struct sigaction sa;
+
+	sa.sa_handler = handler;
+	SAFE_SIGEMPTYSET(&sa.sa_mask);
+	SAFE_SIGACTION(SIGUSR1, &sa, NULL);
+
+	tst_res(TINFO, "Trying to acquire exclusive lock from child");
+	TST_EXP_FAIL(flock(fd, LOCK_EX), EINTR);
+}
+
+static void verify_flock(void)
+{
+	pid_t pid;
+
+	TST_EXP_PASS(flock(fd1, LOCK_EX));
+
+	pid = SAFE_FORK();
+	if (!pid) {
+		child_do(fd2);
+		exit(0);
+	} else {
+		sleep(1);
+		SAFE_KILL(pid, SIGUSR1);
+		SAFE_WAITPID(pid, NULL, 0);
+	}
+}
+
+static struct tst_test test = {
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = verify_flock,
+	.needs_tmpdir = 1,
+	.needs_root = 1,
+	.forks_child = 1,
+};