linux-kernel - Re: [PATCH 3/4] cpu: export cpu hotplug disable/enable functions as global functions

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Date:	Wed, 8 Aug 2012 15:11:26 +0800
From:	Zhao Chenhui <chenhui.zhao@...escale.com>
To:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
CC:	Kumar Gala <galak@...nel.crashing.org>, <rjw@...k.pl>,
	"linuxppc-dev@...ts.ozlabs.org list" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org list" <linux-kernel@...r.kernel.org>,
	Li Yang <leoli@...escale.com>
Subject: Re: [PATCH 3/4] cpu: export cpu hotplug disable/enable functions as
 global functions

On Wed, Aug 08, 2012 at 11:43:22AM +0530, Srivatsa S. Bhat wrote:
> On 08/07/2012 11:21 PM, Kumar Gala wrote:
> > 
> > On Aug 7, 2012, at 3:43 AM, Zhao Chenhui wrote:
> > 
> >> The cpufreq driver of mpc85xx will disable/enable cpu hotplug temporarily.
> >> Therefore, the related functions should be exported.
> >>
> >> Signed-off-by: Zhao Chenhui <chenhui.zhao@...escale.com>
> >> ---
> >> include/linux/cpu.h |    4 ++++
> >> 1 files changed, 4 insertions(+), 0 deletions(-)
> > 
> > Rafael, Srivatsa,
> > 
> > Wanted to get your ack on export these functions for direct calling by arch code.
> >
> 
> Why not just use get_online_cpus()/put_online_cpus()?
> 
> In the case of suspend/resume/hibernation, we had introduced these CPU hotplug disable
> functions because we would end up doing CPU hotplug ourselves, further down the path.
> So if we did a get_online_cpus(), we would end up deadlocking ourselves. Whereas, the
> patch 4/4 looks like a straightforward case of wanting to simply disable CPU hotplug..
> I don't see where you are doing CPU hotplug yourself in the path. So IMO, just
> get/put_online_cpus() should do.
> 
> Regards,
> Srivatsa S. Bhat
> 

Thanks for your comment. I will try to use get/put_online_cpus() in my patch.

-Chenhui

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