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

From	Ingo Molnar <mingo@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/4] cpumask: Migrate 'alloc_cpumask_var()' users to 'zalloc_cpumask_var()'
Date	2015-12-08 05:10 +0100
Message-ID	<qDhLc-5Ko-13@gated-at.bofh.it> (permalink)
References	<qCZOh-2cf-5@gated-at.bofh.it> <qCZOi-2cf-25@gated-at.bofh.it> <qDfgl-43Y-1@gated-at.bofh.it>
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* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> 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.

Sure - that was my original suggestion, will reshape the series to do it like 
that.

Thanks,

	Ingo
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Thread

[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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