linux-kernel - Re: [PATCH 2/2] ehea: add memory remove hotplug support

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Message-Id: <1202166861.7672.11.camel@concordia>
Date:	Tue, 05 Feb 2008 10:14:21 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	Jan-Bernd Themann <ossthema@...ibm.com>
Cc:	Jeff Garzik <jeff@...zik.org>, Thomas Klein <tklein@...ibm.com>,
	Jan-Bernd Themann <themann@...ibm.com>,
	netdev <netdev@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-ppc <linuxppc-dev@...abs.org>,
	Christoph Raisch <raisch@...ibm.com>,
	Marcus Eder <meder@...ibm.com>
Subject: Re: [PATCH 2/2] ehea: add memory remove hotplug support


On Mon, 2008-02-04 at 16:24 +0100, Jan-Bernd Themann wrote:
> On Monday 04 February 2008 15:46, Michael Ellerman wrote:
> > On Mon, 2008-02-04 at 14:04 +0100, Jan-Bernd Themann wrote:
> > > Add memory remove hotplug support
> 
> > > @@ -3559,6 +3578,10 @@ int __init ehea_module_init(void)
> > >  	if (ret)
> > >  		ehea_info("failed registering reboot notifier");
> > >  
> > > +	ret = register_memory_notifier(&ehea_mem_nb);
> > > +	if (ret)
> > > +		ehea_info("failed registering memory remove notifier");
> > > 
> > >  	ret = crash_shutdown_register(&ehea_crash_handler);
> > >  	if (ret)
> > >  		ehea_info("failed registering crash handler");
> > 
> > You don't do anything except print a message if the registration fails.
> > What happens when someone tries to remove memory but the memory notifier
> > wasn't registered properly? Bang?
> 
> In case the registration fails and somebody tries to free memory:
> - Driver will not remove the affected memory from the eHEA memory region
>   --> Firmware (phyp) can not free that memory (as marked as used)
>   --> Therefore the removed memory could not be used in an other partition
> 
> It makes sense to allow the driver to work anyway. Having no ethernet
> would not really be a good alternative.

Yeah I agree. I wasn't clear from the patch that no notifier -> no
memory removed. Rather than, no notifier -> memory removed and ehea
isn't told about it.

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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