linux-kernel - Re: [PATCH 1/1] cpumask: force nr_cpumask_bit to NR_CPUS for CPUMASK

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Message-Id: <200812132025.06514.rusty@rustcorp.com.au>
Date:	Sat, 13 Dec 2008 20:25:05 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Mike Travis <travis@....com>
Cc:	Ingo Molnar <mingo@...e.hu>, David Miller <davem@...emloft.net>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...glemail.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Tony Luck <tony.luck@...el.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	LKML <linux-kernel@...r.kernel.org>, linux-next@...r.kernel.org
Subject: Re: [PATCH 1/1] cpumask: force nr_cpumask_bit to NR_CPUS for CPUMASK_OFFSTACK=n

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.
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