Re: 2.6.10-rc1-mm3: ACPI problem due to un-exported hotplug_path

Kay Sievers
2004-11-05T20:45:39Z

On Fri, Nov 05, 2004 at 12:32:56PM -0800, Ashok Raj wrote:
> On Fri, Nov 05, 2004 at 12:10:12PM -0800, Kay Sievers wrote:
> >
> > On Fri, Nov 05, 2004 at 10:05:13AM -0800, Greg KH wrote:
> > > > The following error (compin from Linus' tree) is caused by the
> > fact that
> > > > hotplug_path is no longer EXPORT_SYMBOL'ed:
> > > >
> > > >
> > > > <-- snip -->
> > > >
> > > > if [ -r System.map ]; then /sbin/depmod -ae -F System.map
> > 2.6.10-rc1-mm3; fi
> >
> > I've found it. This wants to introduce a new direct /sbin/hotplug
> > call,
> > with "add" and "remove" events, without sysfs support.
> >
> > It should use class support or kobject_hotplug() instead. Nobody
> > should
> > fake hotplug events anymore, cause every other notification transport
> > will not get called (currently uevent over netlink).
> >
>
> we were discussing this exact thing recently.. we maybe able to clean this up.. here is why
> we are doing this manual thingy...
>
> When we support physical component hotplug, we want to create the sysfs entries, but that doesnt
> mean the component (i.e CPU or memory) is hotplugged. The reason is for node level hotplug
> there are sequencing requirements, memory needs to be brought up first before cpu, and also
> the error handling/policy requirments which we want the user space to handle it and not from
> kernel side.
>
>
> the sequence is when physical arrival of cpu is seen, we will just create a sysfs entry
> which will also send an add event (which really is just cpu arrival, and sysfs created).
>
> In our model the event is just consumed by the script cpu.agent, which would in turn decide and
> bring the cpu up by
>
> #echo 1> /sys/devices/system/cpu/cpu#/online
>
> what apps really would care about is the ONLINE (which doesnt exist) event itself, and the
> OFFLINE. The ADD/REMOVE only indicate sysfs entries appear and disappear.
>
> I dont know if adding ONLINE/OFFLINE is the right thing, or use the CHANGE notification
> to inform.
>
> This is an area that needs more though which is slightly different from how other devices are being handled.

There is already an "offline" event used for cpu's in drivers/base/cpu.c.
It was recently converted from calling /sbin/hotplug directly :)

ChangeSet: 1.2021
http://linus.bkbits.net:8080/linux-2.5/patch@1.2021?nav=index.html|src/|src/kernel|related/kernel/cpu.c|cset@1.2021

Kay