On 07/14/22 at 04:34pm, Guilherme G. Piccoli wrote: > On 29/06/2022 07:25, Baoquan He wrote: > > Hi, > > > > On a HP machine, after crash triggered via sysrq-c, kdump kernel will > > boot and get soft lockup as below. And this can be always reproduced. > > > > From log, it seems that unreliable tsc was marked as unstable in > > clocksource_watchdog, then worker sched_clock_work was scheduled. And > > this tsc unstable marking always happened after sysrq-c is triggered. > > And the cpu where worker smp_call_function_many_cond is running won't > > be stopped and hang there and keep locks, even though the cpu should be > > stopped. While kdump kernel is running in a different cpu and boot, then > > soft lockup happened because other workers or the relevant threads are > > waiting for locks taken by the hang sched_clock_work worker. > > > > Any idea or suggestion? > > > > The normal kernel boot log and kdump kernel log, kernel config, are all > > attached, please check. > > > > Hi Baoquan, interesting issue! Do you happen to have a full kdump boot > log with the issue? Maybe collected through serial console, etc. > It seems the one attached is from a succeeding kdump by passing > "tsc=unstable" to the kdump kernel right? The attached kdump boot log is the one in which kdump kernel is hang. The 'tsc=unstable' need be added to 1st kernel to work around it. Only adding 'tsc=unstable' into kdump kernel doesn't change anything since the clocksouce_watchdog work has been in a loop because of the unstable tsc in 1st kernel. > > Also, did you try to "forbid" tsc to get marked as unstable in the first > kernel, before kdump? I mean like a hack code change, just prevent > kernel doing that and seeing if it works. If that still fails, then it > seems the cause of the issue is the same as the cause of TSC getting > unstable - in other words, something would be causing both the kdump > kernel lockup AND the TSC unstable marking in the first kernel... As I added later that adding 'tsc=unstable' into 1st kernel's cmdline can work around the issue. kdump works well with that. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
