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From: Rusty Russell <rusty@rustcorp.com.au>
To: Mike Travis <travis@sgi.com>
Subject: Re: [PATCH 1/1] cpumask: force nr_cpumask_bit to NR_CPUS for CPUMASK_OFFSTACK=n
Date: Sat, 13 Dec 2008 20:25:05 +1030
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Cc: Ingo Molnar <mingo@elte.hu>, David Miller <davem@davemloft.net>,
       Paul Mackerras <paulus@samba.org>,
       Martin Schwidefsky <schwidefsky@googlemail.com>,
       Ralf Baechle <ralf@linux-mips.org>, Tony Luck <tony.luck@intel.com>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Stephen Rothwell <sfr@canb.auug.org.au>,
       LKML <linux-kernel@vger.kernel.org>, linux-next@vger.kernel.org
References: <200812082136.33212.rusty@rustcorp.com.au> <200812101019.42908.rusty@rustcorp.com.au> <49417B99.7090004@sgi.com>
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On Friday 12 December 2008 07:14:09 Mike Travis wrote:
> Re: cpumask conversions, or not?
> 
> Rusty Russell wrote:
> > On Tuesday 09 December 2008 21:26:36 Mike Travis wrote:
> >> Rusty Russell wrote:
> >>> Hi all,
> >>>
> >>>    The new cpumask conversions are going well, but unfortunately Stephen
> >>> uncovered a nasty bug via linux-next: the new cpumask operators only go to
> >>> nr_cpumask_bits which can be less than NR_CPUS if NR_CPUS > BITS_PER_LONG.
> >>> The undefined bits confuse the old cpumask operators.  We fixed one case,
> >>> but I am concerned that we will break archs as we convert more core code.
> >> Hi Rusty,
> >>
> >> I think we can avoid this problem if we make cpumask_bits == NR_CPUS iff
> >> CONFIG_CPUMASK_OFFSTACK=n.  This complies with the current cpumask_t
> >> approach and should cause all cpumask operators to always operate on
> >> all cpumask bits.
> > 
> > A very good point.  And it's no worse than the old method.
> > 
> > OK, forget about this for now, no urgent conversions needed :)
> > Rusty.
> 
> This probably should be submitted through linux-next for wider test coverage?

Identical patch already in series.

Thanks,
Rusty.