From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Jens Axboe <jaxboe@fusionio.com>, Tejun Heo <tj@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Shaohua Li <shli@kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
linux-kernel@vger.kernel.org
Subject: Re: Lost IPIs during CPU Hotplug
Date: Tue, 21 May 2013 16:52:43 +0200 [thread overview]
Message-ID: <20130521145243.GA29150@osiris> (raw)
In-Reply-To: <20130520123743.GA4108@osiris>
On Mon, May 20, 2013 at 02:37:43PM +0200, Heiko Carstens wrote:
> I just got a dump from a system running a 3.0.something kernel, however I
> think the problem exists with current kernels as well.
>
> Testcase was some I/O intense workload together with cpu hotplug stress.
>
> When trying to bring a cpu online we got an endless loop on the cpu that
> issued the cpu_up and called smp_call_function_single() within its cpu
> hotplug notifier:
[...]
> It looks to me like the IPI(s) was lost when cpu 3 was brought down before:
[...]
> So it looks to me like yet another CPU_DYING cpu hotplug notifier is needed
> for the generic smp code, which looks for pending IPIs on the to be brought
> down cpu and executes them.
>
> Does that make sense?
Ok, I was able to reproduce it. And the fix should be in the s390 specific
arch code within __cpu_disable() just before the cpu gets removed from the
cpu online mask.
No idea why this never has been seen before.
prev parent reply other threads:[~2013-05-21 14:52 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-20 12:37 Lost IPIs during CPU Hotplug Heiko Carstens
2013-05-21 14:52 ` Heiko Carstens [this message]
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