linux-kernel - Re: frequent lockups in 3.18rc4: revert suggestion

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Message-ID: <470730419.148617.1416204248375.open-xchange@webmail.nmp.skynet.be>
Date:	Mon, 17 Nov 2014 07:04:08 +0100 (CET)
From:	Fabian Frederick <fabf@...net.be>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Dave Jones <davej@...hat.com>, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: frequent lockups in 3.18rc4: revert suggestion



> On 17 November 2014 at 01:35 Linus Torvalds <torvalds@...ux-foundation.org>
> wrote:
>
>
> On Sun, Nov 16, 2014 at 12:42 PM, Fabian Frederick <fabf@...net.be> wrote:
> >
> > Thomas talked about csd_lock and the last reliable stack function
> > being smp_call_function_single, I thought it could be interesting
> > to bisect directly in smp.c as I only read about reverting mm/memory.c
> > stuff ... Maybe not too much original but who knows ? :)
>
> Fair enough.
>
> I'd be almost have been more inclined to look at the apic changes,
> like commit 4ba2968420fa ("percpu: Resolve ambiguities in
> __get_cpu_var/cpumask_var_t") that was horribly buggy. It was fixed in
> 59f6e2073c72, though, and the end result looks sane, so I don't think
> it's that particular thing. The rest seems to be either kvm-related or
> just clearly trivial.
>
> Which is why I think even a partial bisection would be nice - as it is
> we're kind of just guessing, and I'm not all the confident in the
> guesses. Sure, they may be right, but bisection is guaranteed to at
> least narrow the suspects down, while guesses *could* hit jack-pot,
> but could also be a total waste of time.
>
> I guess I'm not much of a gambler. I'll take a steady slow guarantee
> of progress over a jackpot just about every day.
>
>                        Linus

Ok Linus, you're not a gambler but honestly, you created
Git and Linux: the best games I know about on earth ;)

Regards,
Fabian
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