On Wed, 25 Mar 2026 11:25:25 +0900 "Masami Hiramatsu (Google)" <[email protected]> wrote:
> From: Masami Hiramatsu (Google) <[email protected]> > > Add a self-destractive test for the persistent ring buffer. This > will invalidate some sub-buffer pages in the persistent ring buffer > when kernel gets panic, and check whether the number of detected > invalid pages and the total entry_bytes are the same as record > after reboot. > > This can ensure the kernel correctly recover partially corrupted > persistent ring buffer when boot. > > The test only runs on the persistent ring buffer whose name is > "ptracingtest". And user has to fill it up with events before > kernel panics. > > To run the test, enable CONFIG_RING_BUFFER_PERSISTENT_SELFTEST I think a more appropriate config name would be: CONFIG_PERSISTENT_RING_BUFFER_ERROR_INJECT as that's what it is doing as it is only testing error injection and not the persistent ring buffer. > and you have to setup the kernel cmdline; > > reserve_mem=20M:2M:trace trace_instance=ptracingtest^traceoff@trace > panic=1 > > And run following commands after the 1st boot; > > cd /sys/kernel/tracing/instances/ptracingtest > echo 1 > tracing_on > echo 1 > events/enable > sleep 3 > echo c > /proc/sysrq-trigger These instructions should probably be in the CONFIG help message. > > After panic message, the kernel will reboot and run the verification > on the persistent ring buffer, e.g. > > Ring buffer meta [2] invalid buffer page detected > Ring buffer meta [2] is from previous boot! (318 pages discarded) > Ring buffer testing [2] invalid pages: PASSED (318/318) > Ring buffer testing [2] entry_bytes: PASSED (1300476/1300476) BTW, when I tested this, I got the above on the first boot, but if I rebooted normally without re-enabling the persistent ring buffer, I would get on the next boot: [ 0.966510] Ring buffer meta [2] is from previous boot! (0 pages discarded) [ 0.971338] #2 [ 1.003431] Ring buffer meta [3] is from previous boot! (0 pages discarded) [ 1.007737] #3 [ 1.039091] Ring buffer meta [4] is from previous boot! (0 pages discarded) [ 1.043181] Ring buffer testing [4] invalid pages: FAILED (0/1597) [ 1.044660] Ring buffer testing [4] entry_bytes: PASSED (6512464/6512464) [ 1.047829] #4 [ 1.079811] Ring buffer meta [5] is from previous boot! (0 pages discarded) [ 1.083728] #5 [ 1.116764] Ring buffer meta [6] is from previous boot! (0 pages discarded) [ 1.120846] #6 [ 1.156502] Ring buffer meta [7] is from previous boot! (0 pages discarded) [ 1.160857] #7 I'll start testing the previous 3 patches and may add them to next. Also, I noticed that there's nothing that reads the RB_MISSING as I thought it might. I'll have to look into how to pass that info to the trace output. -- Steve
