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Re: [PATCH 1/4] cpumask: Migrate 'alloc_cpumask_var()' users to 'zalloc_cpumask_var()'

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On Mon, Dec 7, 2015 at 12:49 AM, Ingo Molnar <mingo@kernel.org> wrote:
> Xunlei Pang reported a scheduler bug in init_rootdomain(), which is
> caused by improper use of alloc_cpumask_var(), which results in
> uninitialized cpumasks being allocated.
>
> No-one noticed this scheduler bug for a long time, probably because
> alloc_cpumask_var() does result in initialized cpumasks in the
> !CPUMASK_OFFSTACK case - which is the vast majority of systems
> out there.
>
> So migrate all alloc_cpumask_var() users over to zalloc_cpumask_var(),
> to be on the safe side.

Ugh. I'd rather just see us say that "allocating a cpumask always
returns a zeroed mask".

There really is no reason to ever not zero it (they aren't _that_ big
even on huge machines), so I'd rather just get rid of the "zalloc"
version that is the less common one anyway.

                 Linus
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[PATCH 0/4] [RFC] cpumask: Robustify the var-cpumask allocation APIs Ingo Molnar <mingo@kernel.org> - 2015-12-07 10:00 +0100
  [PATCH 1/4] cpumask: Migrate 'alloc_cpumask_var()' users to 'zalloc_cpumask_var()' Ingo Molnar <mingo@kernel.org> - 2015-12-07 10:00 +0100
    Re: [PATCH 1/4] cpumask: Migrate 'alloc_cpumask_var()' users to 'zalloc_cpumask_var()' Linus Torvalds <torvalds@linux-foundation.org> - 2015-12-08 02:30 +0100
      Re: [PATCH 1/4] cpumask: Migrate 'alloc_cpumask_var()' users to  'zalloc_cpumask_var()' Ingo Molnar <mingo@kernel.org> - 2015-12-08 05:10 +0100
        Re: [PATCH 1/4] cpumask: Migrate 'alloc_cpumask_var()' users to  'zalloc_cpumask_var()' Ingo Molnar <mingo@kernel.org> - 2015-12-08 05:20 +0100

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