Hi, On 2015/06/23 23:05, dwalker@xxxxxxxxxx wrote: > > Hi, > > There was a commit in kernel/panic.c which altered when the kexec crash kernel is executed, > > commit f06e5153f4ae2e2f3b0300f0e260e40cb7fefd45 > Author: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx> > Date: Fri Jun 6 14:37:07 2014 -0700 > > kernel/panic.c: add "crash_kexec_post_notifiers" option for kdump after panic_notifers > > > This made it possible for smp_send_stop() to be executed prior to calling the kexec crash > kernel. > > The issue is that smp_send_stop() offlines the cores, and other code depend on the cores being online. > > In my case on Octeon here's an example, > > panic() > crash_kexec() > machine_crash_shutdown() > octeon_generic_shutdown() > > Inside octeon_generic_shutdown() the Octeon watchdog is shutdown for_each_online_cpu(), but since > most of the cpu's already got offlined in smp_send_stop() it means the watchdog is still alive on > those cores. This results in a reboot during the crash kernel execution. Ah, I see. > Another example seem to be in default_machine_crash_shutdown() where crash_kexec_prepare_cpus() depends > on an IPI for saving the registers on different cores. However, the cpu's are all offlined with > interrupts disabled so they won't be running those IPI's in this case. > > I'm looking for any advice on how this should be fixed, or if it's already fixed. I'm not going to be > submitting a patch so if anyone wants to submit one feel free to do so. Hmm, IMHO, when the cpu goes to offline in appropriate way(smp_send_stop), it should stop watchdog timer on the offlined cpu too. Or, you can also register crash handler which stops all watchdogs, but it's a bit tricky. Thank you, -- Masami HIRAMATSU Linux Technology Research Center, System Productivity Research Dept. Center for Technology Innovation - Systems Engineering Hitachi, Ltd., Research & Development Group E-mail: masami.hiramatsu.pt@xxxxxxxxxxx
