[LTP] [PATCH] checkpoint: add test for child reinitializing checkpoint region

[Li Wang]

This adds a pair of tests that verify checkpoint synchronization across
a parent and a re-exec'd child. The child process uses `tst_reinit()` to
reconnect to the shared checkpoint memory region established by the parent.

The parent waits on checkpoint 0, while the child wakes it after verifying
CLI arguments and reinitializing the IPC region.

Follow-up: https://lists.linux.it/pipermail/ltp/2025-June/044063.html
Signed-off-by: Li Wang <liwang@redhat.com>
---
 lib/newlib_tests/.gitignore              |  2 ++
 lib/newlib_tests/runtest.sh              |  4 +++
 lib/newlib_tests/tst_checkpoint_child.c  | 27 +++++++++++++++++
 lib/newlib_tests/tst_checkpoint_parent.c | 38 ++++++++++++++++++++++++
 4 files changed, 71 insertions(+)
 create mode 100644 lib/newlib_tests/tst_checkpoint_child.c
 create mode 100644 lib/newlib_tests/tst_checkpoint_parent.c

diff --git a/lib/newlib_tests/.gitignore b/lib/newlib_tests/.gitignore
index 3545f5ac5..a4984d2ec 100644
--- a/lib/newlib_tests/.gitignore
+++ b/lib/newlib_tests/.gitignore
@@ -16,6 +16,8 @@ tst_capability02
 tst_cgroup01
 tst_cgroup02
 tst_checkpoint
+tst_checkpoint_parent
+tst_checkpoint_child
 tst_checkpoint_wait_timeout
 tst_checkpoint_wake_timeout
 tst_device
diff --git a/lib/newlib_tests/runtest.sh b/lib/newlib_tests/runtest.sh
index f2133d365..d87751c2f 100755
--- a/lib/newlib_tests/runtest.sh
+++ b/lib/newlib_tests/runtest.sh
@@ -18,6 +18,10 @@ test1[59]
 test2[04]
 tst_bool_expr
 tst_capability02
+tst_checkpoint
+tst_checkpoint_parent
+tst_checkpoint_wait_timeout
+tst_checkpoint_wake_timeout
 tst_device
 tst_expiration_timer
 tst_fuzzy_sync0[1-3]
diff --git a/lib/newlib_tests/tst_checkpoint_child.c b/lib/newlib_tests/tst_checkpoint_child.c
new file mode 100644
index 000000000..c4eaccacc
--- /dev/null
+++ b/lib/newlib_tests/tst_checkpoint_child.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Child process: this binary is expected to be exec'd by the parent.
+ *
+ * It reinitializes the shared memory region using tst_reinit(),
+ * verifies the command-line argument, and signals checkpoint 0.
+ */
+
+#define TST_NO_DEFAULT_MAIN
+#include "tst_test.h"
+#include "tst_checkpoint.h"
+
+int main(int argc, char *argv[])
+{
+	tst_reinit();
+
+	if (argc != 2)
+		tst_brk(TFAIL, "argc is %d, expected 2", argc);
+
+	if (strcmp(argv[1], "canary"))
+		tst_brk(TFAIL, "argv[1] is %s, expected 'canary'", argv[1]);
+
+	tst_res(TINFO, "Child: signaling checkpoint");
+	TST_CHECKPOINT_WAKE(0);
+
+	return 0;
+}
diff --git a/lib/newlib_tests/tst_checkpoint_parent.c b/lib/newlib_tests/tst_checkpoint_parent.c
new file mode 100644
index 000000000..9d7f1783b
--- /dev/null
+++ b/lib/newlib_tests/tst_checkpoint_parent.c
@@ -0,0 +1,38 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Parent process: spawns a child which reinitializes checkpoint region
+ * using tst_reinit(). Waits for a checkpoint signal from the child.
+ */
+
+#include <errno.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+#include "tst_test.h"
+#include "tst_checkpoint.h"
+
+static void run(void)
+{
+	pid_t pid = SAFE_FORK();
+
+	if (pid == 0) {
+		TEST(execlp("tst_checkpoint_child", "tst_checkpoint_child", "canary", NULL));
+		tst_brk(TFAIL | TTERRNO, "Failed to execute tst_checkpoint_child");
+	}
+
+	TST_CHECKPOINT_WAIT(0);
+	tst_res(TPASS, "Parent: checkpoint reached");
+
+	SAFE_WAITPID(pid, NULL, 0);
+
+	return;
+}
+
+static struct tst_test test = {
+	.forks_child = 1,
+	.needs_checkpoints = 1,
+	.child_needs_reinit = 1,
+	.test_all = run,
+};
-- 
2.50.0