[PATCH v2 1/1] kexec: dump kmessage before machine_kexec

[Pavel Tatashin]

On Thu, Jan 28, 2021 at 3:01 PM Eric W. Biederman <ebiederm at xmission.com> wrote:
>
> Pavel Tatashin <pasha.tatashin at soleen.com> writes:
>
> > kmsg_dump(KMSG_DUMP_SHUTDOWN) is called before
> > machine_restart(), machine_halt(), machine_power_off(), the only one that
> > is missing is  machine_kexec().
> >
> > The dmesg output that it contains can be used to study the shutdown
> > performance of both kernel and systemd during kexec reboot.
> >
> > Here is example of dmesg data collected after kexec:
>
> As long was we keep kmsg_dump out of the crash_kexec path where
> it completely breaks kexec on panic this seems a reasonable thing to do.
> On the ordinary kernel_kexec path everything is expected to be working.

This is an ordinary kexec reboot path, not kdump.

>
> Is kmsg_dump expected to work after all of the device drivers
> are shut down?  Otherwise this placement of kmsg_dump is too late.

Yes it is. It is called after device_shutdown(); in all other places.


Thank you,
Pasha