linux-kernel - Re: smp_call_function

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Date:	Tue, 31 Mar 2015 16:07:32 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Chris J Arges <chris.j.arges@...onical.com>
Cc:	Rafael David Tinoco <inaddy@...ntu.com>,
	Ingo Molnar <mingo@...nel.org>, Peter Anvin <hpa@...or.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jens Axboe <axboe@...nel.dk>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Gema Gomez <gema.gomez-solano@...onical.com>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: smp_call_function_single lockups

On Tue, Mar 31, 2015 at 3:23 PM, Chris J Arges
<chris.j.arges@...onical.com> wrote:
>
> I had a few runs with your patch plus modifications, and got the following
> results (modified patch inlined below):

Ok, thanks.

> [   14.423916] ack_APIC_irq: vector = d1, irq = ffffffff
> [  176.060005] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [qemu-system-x86:1630]
>
> [   17.995298] ack_APIC_irq: vector = d1, irq = ffffffff
> [  182.993828] ack_APIC_irq: vector = e1, irq = ffffffff
> [  202.919691] ack_APIC_irq: vector = 22, irq = ffffffff
> [  484.132006] NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [qemu-system-x86:1586]
>
> [   15.592032] ack_APIC_irq: vector = d1, irq = ffffffff
> [  304.993490] ack_APIC_irq: vector = e1, irq = ffffffff
> [  315.174755] ack_APIC_irq: vector = 22, irq = ffffffff
> [  360.108007] NMI watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [ksmd:26]
.. snip snip ..

So yeah, that's VECTOR_UNDEFINED, and while it could happen as part of
irq setup, I'm not seeing that being something that your load should
trigger.

It could also obviously just be the vector being somehow corrupted,
either due to crazy hardware or software.

But quite frankly, the most likely reason is that whole irq vector movement.

Especially since it sounds from your other email that when you apply
Ingo's patches, the ack_APIC_irq warnings go away. Is that correct? Or
did you just grep for "move" in the messages?

If you do get both movement messages (from Info's patch) _and_ the
ack_APIC_irq warnings (from mine), it would be interesting to see if
the vectors line up somehow..

                     Linus
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