On Fri, 27 Mar 2026 16:25:08 -0400 Steven Rostedt <[email protected]> wrote:
> 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. OK, selftest will be another implementation. (preparing buffer with test data and check recovery process?) > > > 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. OK. I'll add it. > > > > > 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: Hmm, since it is already recovered (rewound) the 2nd rewound process may not work correctly. Let me fix it. > > > [ 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. Thanks, > > 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 > -- Masami Hiramatsu (Google) <[email protected]>
