linux-kernel - Re: [patch] add kdump_after

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Date:	Tue, 14 Aug 2007 18:54:54 +0530
From:	Vivek Goyal <vgoyal@...ibm.com>
To:	Takenori Nagano <t-nagano@...jp.nec.com>,
	Keith Owens <kaos@....com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	k-miyoshi@...jp.nec.com, kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch] add kdump_after_notifier

On Tue, Aug 14, 2007 at 10:37:10AM +0200, Bernhard Walle wrote:
> * Takenori Nagano <t-nagano@...jp.nec.com> [2007-08-14 10:34]:
> > Vivek Goyal wrote:
> > > On Fri, Aug 03, 2007 at 02:05:47PM +1000, Keith Owens wrote:
> > > 
> > > 
> > > To sum up, couple of options come to mind.
> > > 
> > > - Register all the RAS tools on die notifier and panic
> > >   notifier lists with fairly high priority. Export list
> > >   of RAS tools to user space and allow users to decide the
> > >   order of execution and priority of RAS tools.
> > > 
> > > - Create a separate RAS tool notifier list (ras_tool_notifer_list).
> > >   All the RAS tools register on this list. This list gets priority
> > >   over die or panic notifier list. User decides the oder of execution
> > >   of RAS tools. 
> > > 
> > >   Here assumption is that above list will not be exported to modules.
> > >   All the RAS tools will be in kernel and they always get a priority
> > >   to inspect an event.
> > > 
> > > What do others think?
> > 
> > Very good idea. But there is a problem how to give default priority to RAS tools.
> > 
> > How about priority changeable notifier_list? User can change list order
> > dynamically if they want. Of course, we have to give highest priority to kdump
> > by default. It is very useful for users who want to use some RAS tools.
> 
> I think that was the idea of the first “-” (“export list of RAS tools
> to user space”).
> 

So for the time being I think we can put RAS tools on die notifier list
and if it runs into issues we can always think of creating a separate list.

Few things come to mind.

- Why there is a separate panic_notifier_list? Can't it be merged with
  die_chain? die_val already got one of the event type as PANIC. If there
  are no specific reasons then we should merge the two lists. Registering
  RAS tools on a single list is easier.
- Modify Kdump to register on die_chain list. 
- Modify Kdb to register on die_chain list.
- Export all the registered members of die_chain through sysfs along with
  their priorities. Priorities should be modifiable. Most likely one 
  shall have to introduce additional field in struct notifier_block. This
  field will be a string as an identifier of the user registerd. e.g
  "Kdump", "Kdb" etc.

Now user will be able to view all the die_chain users through sysfs and
be able to modify the order in which these should run by modifying their
priority. Hence all the RAS tools can co-exist.

Any thoughts?

Thanks
Vivek




> 
> Thanks,
>    Bernhard
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