Re: [RFC] KEXEC: allocate crash note buffers at boot time

[Keir Fraser <keir.xen@gmail.com>]

On 29/11/2011 18:56, "Andrew Cooper" <andrew.cooper3@citrix.com> wrote:

> Hello,
> 
> As I have little to no knowledge of this stage of the boot process, is
> this a sensible way to be setting up the per_cpu areas?  I have a
> sneaking suspicion that it will fall over if a CPU is onlined after
> boot, and may also fall over if a CPU is offlined and reonlined later.
> There appears to be no infrastructure currently in place for this type
> of initialization, which is quite possibly why the code exists in its
> current form.

No it's bad. For starters you should use for_each_online_cpu, not do an
open-coded for-loop. Secondly you should register a cpu hotplug notifier
(register_cpu_notifier()) to pick up and handle future
CPU_UP_PREPARE/CPU_UP_CANCELED/CPU_DEAD events. This can be hung off an
__initcall. See common/stop_machine.c for example, or common/timer.c, which
doesn't even require a for_each_online_cpu loop because its init code gets
run before we bring up secondary CPUs.

 -- Keir 

> Thanks,