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			| Re: [ckrm-tech] [PATCH 4/6] containers: Simple CPU accounting container subsystem [message #9591 is a reply to message #9573] | Fri, 12 January 2007 00:33   |  
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					|  Paul Menage Messages: 642
 Registered: September 2006
 | Senior Member |  |  |  
	| On 1/10/07, Balbir Singh <balbir@in.ibm.com> wrote: >
 > I have run into a problem running this patch on a powerpc box. Basically,
 > the machine panics as soon as I mount the container filesystem with
 
 This is a multi-processor system?
 
 My guess is that it's a race in the subsystem API that I've been
 meaning to deal with for some time - basically I've been using
 (<foo>_subsys.subsys_id != -1) to indicate that <foo> is ready for
 use, but there's a brief window during subsystem registration where
 that's not actually true.
 
 I'll add an "active" field in the container_subsys structure, which
 isn't set until registration is completed, and subsystems should use
 that instead. container_register_subsys() will set it just prior to
 releasing callback_mutex, and cpu_acct.c (and other subsystems) will
 check <foo>_subsys.active rather than (<foo>_subsys.subsys_id != -1)
 
 > I am trying to figure out the reason for the panic and trying to find
 > a fix. Since the introduction of whole hierarchy system, the debugging
 > has gotten a bit harder and taking longer, hence I was wondering if you
 > had any clues about the problem
 >
 
 Yes, the multi-hierarchy support does make the whole code a little
 more complex - but people presented reasonable scenarios where a
 single container tree for all resource controllers just wasn't
 flexible enough.
 
 Paul
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