linux-kernel - RE: [PATCH] drivers: base: update cpu offline info when do hotplug

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Date:	Tue, 21 Oct 2014 18:32:14 -0700
From:	Neil Zhang <zhangwm@...vell.com>
To:	Dan Streetman <ddstreet@...e.org>
CC:	linux-kernel <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: RE: [PATCH] drivers: base: update cpu offline info when do hotplug

Dan,

> -----Original Message-----
> From: ddstreet@...il.com [mailto:ddstreet@...il.com] On Behalf Of Dan
> Streetman
> Sent: 2014年10月21日 21:03
> To: Neil Zhang
> Cc: linux-kernel; Greg Kroah-Hartman
> Subject: Re: [PATCH] drivers: base: update cpu offline info when do hotplug
> 
> On Sun, Oct 19, 2014 at 11:29 PM, Neil Zhang <zhangwm@...vell.com> wrote:
> > The current per-cpu offline info won't be updated if it is hotplugged
> > in/out by a kernel governer.
> > Let's update it via cpu notifier.
> >
> > Signed-off-by: Neil Zhang <zhangwm@...vell.com>
> > ---
> >  drivers/base/cpu.c |   25 +++++++++++++++++++++++++
> >  1 file changed, 25 insertions(+)
> >
> > diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c index
> > 006b1bc..9d61824 100644
> > --- a/drivers/base/cpu.c
> > +++ b/drivers/base/cpu.c
> > @@ -418,10 +418,35 @@ static void __init
> > cpu_dev_register_generic(void)  #endif  }
> >
> > +static int device_hotplug_notifier(struct notifier_block *nfb,
> > +                                     unsigned long action, void
> > +*hcpu) {
> > +       unsigned int cpu = (unsigned long)hcpu;
> > +       struct device *dev = get_cpu_device(cpu);
> > +       int ret;
> > +
> > +       switch (action & ~CPU_TASKS_FROZEN) {
> > +       case CPU_ONLINE:
> > +               dev->offline = false;
> > +               ret = NOTIFY_OK;
> > +               break;
> > +       case CPU_DYING:
> > +               dev->offline = true;
> 
> one thing i just thought of here, since dev->offline is getting set here, can
> you remove it being set in drivers/base/core.c at
> device_online() and device_offline() ?  That's probably redundant now right?

Yes, I ever thought about it.
But I'm not sure whether some other devices (such as memory) will use it later too.
So I still kept it there since seems won't cause any problem.

> 
> 
> > +               ret = NOTIFY_OK;
> > +               break;
> > +       default:
> > +               ret = NOTIFY_DONE;
> > +               break;
> > +       }
> > +
> > +       return ret;
> > +}
> > +
> >  void __init cpu_dev_init(void)
> >  {
> >         if (subsys_system_register(&cpu_subsys, cpu_root_attr_groups))
> >                 panic("Failed to register CPU subsystem");
> >
> >         cpu_dev_register_generic();
> > +       cpu_notifier(device_hotplug_notifier, 0);
> >  }
> > --
> > 1.7.9.5
> >
> > --
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Best Regards,
Neil Zhang