Re: [PATCH v2:3/3]Export cpu topology by sysfs

Greg KH
2005-12-27T05:36:10Z

On Mon, Dec 26, 2005 at 12:28:39AM -0800, Yanmin Zhang wrote:
> On Mon, Dec 26, 2005 at 03:38:16PM +0800, Zhang, Yanmin wrote:
> > >>-----Original Message-----
> > >>From: Greg KH [mailto:greg@kroah.com]
> > >>Sent: 2005??12??24?? 3:16
> > >>To: Zhang, Yanmin
> > >>Cc: Yanmin Zhang; linux-kernel@vger.kernel.org; discuss@x86-64.org; linux-ia64@vger.kernel.org; Siddha, Suresh B; Shah, Rajesh;
> > >>Pallipadi, Venkatesh
> > >>Subject: Re: [PATCH v2:3/3]Export cpu topology by sysfs
> > >>
> > >>On Fri, Dec 23, 2005 at 12:03:27PM +0800, Zhang, Yanmin wrote:
> > >>> >>Can't you just use an attribute group and attach it to the cpu kobject?
> > >>> >>That would save an array of kobjects I think.
> > >>> As you know, current i386/x86_64 arch also export cache info under
> > >>> /sys/device/system/cpu/cpuX/cache. Is it clearer to export topology
> > >>> under a new directory than under cpu directly?
> > >>
> > >>No, the place in the sysfs tree you are putting this is just fine. I'm
> > >>just saying that you do not need to create a new kobject for these
> > >>attributes. Just use an attribute group, and you will get the same
> > >>naming, without the need for an extra kobject (and the whole array of
> > >>kobjects) at all.
> > >>
> > >>Does that make more sense?
> > Yes, indeed. Now, I used your idea and the patch became simpler. Thanks.

> >
> >
> > >>
> > >>> >>> +static int __cpuinit topology_cpu_callback(struct notifier_block *nfb,
> > >>> >>> + unsigned long action, void *hcpu)
> > >>> >>> +{
> > >>> >>> + unsigned int cpu = (unsigned long)hcpu;
> > >>> >>> + struct sys_device *sys_dev;
> > >>> >>> +
> > >>> >>> + sys_dev = get_cpu_sysdev(cpu);
> > >>> >>> + switch (action) {
> > >>> >>> + case CPU_ONLINE:
> > >>> >>> + topology_add_dev(sys_dev);
> > >>> >>> + break;
> > >>> >>> +#ifdef CONFIG_HOTPLUG_CPU
> > >>> >>> + case CPU_DEAD:
> > >>> >>> + topology_remove_dev(sys_dev);
> > >>> >>> + break;
> > >>> >>> +#endif
> > >>> >>
> > >>> >>Why ifdef? Isn't it safe to just always have this in?
> > >>> If no ifdef here, gcc reported a compiling warning when I compiled it
> > >>> on IA64 with CONFIG_HOTPLUG_CPU=n.
> > >>
> > >>Then you should probably go change it so that CPU_DEAD is defined on
> > >>non-smp builds, otherwise the code gets quite messy like the above :)
> >
> > Sorry. My previous explanation is confusing. It's a link warning on ia64. On ia64, the kernel vmlinux doesn't include section .exit.text, so ld will report a link warning when a function is in section .exit.text and another function (not in .exit.text) calls the first one. When CONFIG_HOTPLUG_CPU=n, function topology_remove_dev is in section .exit.text, but its caller topology_remove_dev is not in .exit.text.
> >
> > i386 and x86_64 kernel vmlinux does include .exit.text and discard it only when running, so there is no such warning on i386/x86_64.
> >
> > There is no other better approach to get rid of the warning unless we change arch/ia64/kernel/vmlinux.lds.S to keep all .exit.text in kernel image.
>
> Here is the new patch. Thank Greg.

Much nicer, thanks for the changes. But you forgot the description and
the Signed-off-by: line so that it can be picked up :(

Care to try again?

thanks,

greg k-h