Date: Fri, 5 Nov 2004 12:32:56 -0800
From: Ashok Raj <ashok.raj@intel.com>
To: Kay Sievers <kay.sievers@vrfy.org>
Cc: Greg KH <greg@kroah.com>, Adrian Bunk <bunk@stusta.de>,
       Andrew Morton <akpm@osdl.org>, rml@novell.com,
       linux-kernel@vger.kernel.org, "Brown, Len" <len.brown@intel.com>,
       acpi-devel@lists.sourceforge.net, rusty@rustycorp.com.au
Subject: Re: 2.6.10-rc1-mm3: ACPI problem due to un-exported hotplug_path
Message-ID: <20041105123254.A17224@unix-os.sc.intel.com>
References: <20041105201012.GA24063@vrfy.org>
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In-Reply-To: <20041105201012.GA24063@vrfy.org>; from kay.sievers@vrfy.org on Fri, Nov 05, 2004 at 12:10:12PM -0800
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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.

Greg-kh/Rusty .. any suggestions


Cheers,
Ashok Raj
- Linux OS & Technology Team
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