Re: [PATCH -v6 2/5] Migrate shutdown/reboot to boot cpu.

From: Ingo Molnar
Date: Thu Apr 25 2013 - 02:57:15 EST



* Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Wed, 24 Apr 2013 06:18:50 -0500 Robin Holt <holt@xxxxxxx> wrote:
>
> > We recently noticed that reboot of a 1024 cpu machine takes approx 16
> > minutes of just stopping the cpus. The slowdown was tracked to commit
> > f96972f.
> >
> > The current implementation does all the work of hot removing the cpus
> > before halting the system. We are switching to just migrating to the
> > boot cpu and then continuing with shutdown/reboot.
> >
> > This also has the effect of not breaking x86's command line parameter for
> > specifying the reboot cpu. Note, this code was shamelessly copied from
> > arch/x86/kernel/reboot.c with bits removed pertaining to the reboot_cpu
> > command line parameter.
> >
> > @@ -357,6 +357,24 @@ int unregister_reboot_notifier(struct notifier_block *nb)
> > }
> > EXPORT_SYMBOL(unregister_reboot_notifier);
> >
> > +static void migrate_to_reboot_cpu(void)
> > +{
> > + /* The boot cpu is always logical cpu 0 */
> > + int reboot_cpu_id = 0;
> > +
> > + cpu_hotplug_disable();
> > +
> > + /* Make certain the cpu I'm about to reboot on is online */
> > + if (!cpu_online(reboot_cpu_id))
> > + reboot_cpu_id = cpumask_first(cpu_online_mask);
> > +
> > + /* Prevent races with other tasks migrating this task */
> > + current->flags |= PF_THREAD_BOUND;
>
> PF_THREAD_BOUND was removed/replaced in linux-next's a9ab775bc
> ("workqueue: directly restore CPU affinity of workers from CPU_ONLINE")

I don't see PF_THREAD_BOUND being removed by commit a9ab775bc. Did you
mean some other commit?

Thanks,

Ingo
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