linux-kernel - Re: Random panic in load

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Message-ID: <20140723182413.GC3935@laptop>
Date:	Wed, 23 Jul 2014 20:24:13 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Dietmar Eggemann <dietmar.eggemann@....com>,
	Michel Dänzer <michel@...nzer.net>,
	Ingo Molnar <mingo@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Random panic in load_balance() with 3.16-rc

On Wed, Jul 23, 2014 at 10:12:35AM -0700, Linus Torvalds wrote:
> On Wed, Jul 23, 2014 at 10:03 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> > On Wed, Jul 23, 2014 at 09:54:23AM -0700, Linus Torvalds wrote:
> >>
> >> And I wonder if I have a clue. Look, load_balance_mask is a
> >> "cpumask_var_t", but I don't see a "alloc_cpumask_var()" for it.
> >> That's broken with CONFIG_CPUMASK_OFFSTACK.
> >
> > kernel/sched/core.c:sched_init()
> >
> > plays horrible allocation tricks..
> 
> No it does not. It allocates a cpumask. Nothing more. If you think it
> allocates a "cpumask_var()", you are wrong.

I was merely saying 'something' got allocated, but yes I'll agree its
not a cpumask_var_t thingy.

> I agree that the code is an unreadable mess, but that's what
> "cpumask_size()" is: the minimum required size of the bitmask in a
> cpumask.

Latest patch cures at least this part of that mess.
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