Re: [PATCH] Fix interrupt distribution in ppc970

[Michael Ellerman <michael@ellerman.id.au>]

[-- Attachment #1: Type: text/plain, Size: 2112 bytes --]

On Wed, 2007-03-07 at 10:23 +0530, Mohan Kumar M wrote:
> On Tue, Mar 06, 2007 at 06:37:14PM +0100, Michael Ellerman wrote:
> > On Tue, 2007-03-06 at 22:25 +0530, Mohan Kumar M wrote:
> > > On Tue, Mar 06, 2007 at 03:16:55PM +0100, Michael Ellerman wrote:
> > > > First, I don't know why we keep telling people to use maxcpus=1 for
> > > > kexec/kdump - it's causing bugs, and I don't know of any that it fixes?
> > > 
> > > Some distros want to use maxcpus=1 for kdump.
> > 
> > Yeah OK.
> > 
> > > > Second, the way you've written this is not so good. The xics code should
> > > > not be checking that "maxcpus" exists on the command line, it should be
> > > > checking that the distrib server points to a cpu that is online - using
> > > > cpu_online() etc.
> > > >
> > > 
> > > In get_irq_server function in xics.c, "noirqdistrib" command line
> > > parameter is indirectly checked for routing the interrupts either to a
> > > specific cpu or to all cpus. So I think checking for maxcpus= command
> > > line parameter in xics.c is not a problem.
> > 
> > No, it checks a flag, it doesn't run strstr on the saved command line.
> >
> What if I use a flag (or existing global variable if any) to check for
> the presence of maxcpus kernel paramter?

There's already maxcpus in init/main.c, that would probably be better,
though still ugly.

> > > Also during the xics_init_IRQ function other cpus (secondary cpus) will
> > > not be online, they are made online at a later stage. So using
> > > cpu_online() function at xics_init_IRQ will return true only for boot
> > > cpu id.
> > 
> > OK, so you should be able to use cpus possible map or something similar.
> >
> Hmm, I think cpus possible map will have an entry for the offline cpu
> also.

You're right, it will, did I mention that maxcpus= is broken :)

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

[-- Attachment #2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 189 bytes --]