Re: [PATCH v3 4/4] selftests/ftrace: Add persistent ring buffer testcases
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Date: 2026-08-12 12:49:50
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sashiko-reviews
On Wed, 12 Aug 2026 00:57:31 +0000 sashiko-bot@kernel.org wrote:
quoted hunk ↗ jump to hunk
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [Medium] Test enters an infinite reboot loop if the persistent trace feature fails. ----- Patch [4]: [PATCH v3 4/4] selftests/ftrace: Add persistent ring buffer testcases ---commit d365a5483f67b1295e536e6d26fd4ee7166e27b3 Author: Masami Hiramatsu (Google) [off-list ref] selftests/ftrace: Add persistent ring buffer testcases Add test cases for persistent ring buffer and backup instance across guest crash/reboot. These verify trace data retention in the boot_map instance and preservation in the backup instance on subsequent boot.quoted
diff --git a/tools/testing/selftests/ftrace/boottime/tests/persistent-01-reserve-mem.sh b/tools/testing/selftests/ftrace/boottime/tests/persistent-01-reserve-mem.sh new file mode 100644 index 0000000000000..49abaf518481f --- /dev/null +++ b/tools/testing/selftests/ftrace/boottime/tests/persistent-01-reserve-mem.sh@@ -0,0 +1,28 @@[ ... ]quoted
+ +# Check if Boot 1 marker was already written +if grep -q "BOOT1_MARKER" "$TRACEDIR/instances/boot_map/trace" 2>/dev/null; then + # Second boot: verify persistent ring buffer content from first boot + echo "PASS: persistent-01-reserve-mem" + exit 0 +fi + +# First boot: write marker to persistent buffer and trigger kernel crash/reboot +echo "BOOT1_MARKER" > "$TRACEDIR/instances/boot_map/trace_marker" +sync + +# Trigger reboot to restart into second boot +echo b > /proc/sysrq-trigger 2>/dev/null || echo c > /proc/sysrq-trigger 2>/dev/null || true[Severity: Medium] If the persistent trace feature fails to retain the BOOT1_MARKER across reboot, could this script enter an infinite reboot loop? Since the test falls through to the first-boot logic when the marker is missing, it appears it will write the marker and reboot again indefinitely. This might cause the test to run until it is killed by a global timeout rather than failing cleanly.
Yes, that is why I made the timeout command required. Since the test uses only initramfs, we can not save the state on it. Of course we can use virtio-fs or something like it, but it is too much. If we can handle such failure via timeout, it is good enough.
quoted
+sleep 5 +echo "FAIL: reboot trigger failed on first boot" +exit 1diff --git a/tools/testing/selftests/ftrace/boottime/tests/persistent-02-backup-instance.sh b/tools/testing/selftests/ftrace/boottime/tests/persistent-02-backup-instance.sh new file mode 100644 index 0000000000000..0b2a2f03ce4f2 --- /dev/null +++ b/tools/testing/selftests/ftrace/boottime/tests/persistent-02-backup-instance.sh@@ -0,0 +1,40 @@[ ... ]quoted
+ +# Check if BOOT1_MARKER is in boot_map/trace (indicates second boot) +if grep -q "BOOT1_MARKER" "$TRACEDIR/instances/boot_map/trace" 2>/dev/null; then + # Second boot: verify BOOT1_MARKER was copied into backup/trace from Boot 1 + if grep -q "BOOT1_MARKER" "$TRACEDIR/instances/backup/trace" 2>/dev/null; then + echo "PASS: persistent-02-backup-instance" + exit 0 + else + echo "FAIL: BOOT1_MARKER found in boot_map/trace" \ + "but missing from backup/trace on second boot" + exit 1 + fi +fi + +# First boot: write BOOT1_MARKER to boot_map and reboot via sysrq-trigger +echo "BOOT1_MARKER" > "$TRACEDIR/instances/boot_map/trace_marker" +sync + +# Trigger reboot to restart into second boot +echo b > /proc/sysrq-trigger 2>/dev/null || echo c > /proc/sysrq-trigger 2>/dev/null || true[Severity: Medium] Similarly, does this script also risk an infinite reboot loop if the marker is missing from boot_map/trace on the second boot? It looks like it would also fall back to triggering another reboot instead of reporting a failure.
Ditto. It is eventually handled by timeout failure. Thank you, -- Masami Hiramatsu (Google) [off-list ref]