From: "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>
To: Jeff Moyer <jmoyer@redhat.com>
Cc: Sasha Levin <levinsasha928@gmail.com>,
Nick Bowler <nbowler@elliptictech.com>,
linux-kernel@vger.kernel.org, Kay Sievers <kay.sievers@vrfy.org>
Subject: Re: the maxcpus= boot parameter broke somewhere along the line
Date: Mon, 02 Apr 2012 20:02:49 +0530 [thread overview]
Message-ID: <4F79B891.8020704@linux.vnet.ibm.com> (raw)
In-Reply-To: <x49wr5ygrfx.fsf@segfault.boston.devel.redhat.com>
On 04/02/2012 07:35 PM, Jeff Moyer wrote:
> "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com> writes:
>
>> Looking at the mention of udev above, and considering the commit you bisected
>> to, I think it would be good to see whether someone is writing 1 to
>> /sys/device/system/cpu/cpu*/online and hence the cpus are getting hot-added
>> towards the end of boot. Maybe that sounds stupid, but worth a try :)
>>
>> So can you try the debug patch below? It applies on latest linux-3.3-rc6+
>
> Sorry it took me so long to get back to you. You're patch did, in fact,
> trigger:
>
> udev: starting version 147
> CPU 3 online initated from userspace
> SMP alternatives: switching to SMP code
> WARNING! power/level is deprecated; use power/control instead
> Booting Node 0 Processor 3 APIC 0x3
> NMI watchdog: enabled, takes one hw-pmu counter.
> CPU 1 online initated from userspace
> Booting Node 0 Processor 1 APIC 0x2
> NMI watchdog: enabled, takes one hw-pmu counter.
> CPU 2 online initated from userspace
> Booting Node 0 Processor 2 APIC 0x1
> NMI watchdog: enabled, takes one hw-pmu counter.
> CPU 1 online initated from userspace
> CPU 3 online initated from userspace
> CPU 2 online initated from userspace
>
Aha! Just like I thought!
So there is no kernel bug with respect to the maxcpus= boot parameter :-)
Regards,
Srivatsa S. Bhat
> Checking through udev rules, I found this in
> /lib/udev/rules.d/40-redhat.rules (this is a RHEL 6 install, btw):
>
> ACTION=="add", KERNEL=="cpu[0-9]*", RUN+="/bin/bash -c 'echo 1 > /sys/devices/system/cpu/%k/online'"
>
> So, what do you suppose is the right way to fix this?
>
> Cheers,
> Jeff
>
> Kay, you can read up on the rest of the thread here:
> https://lkml.org/lkml/2012/3/6/242
>
next prev parent reply other threads:[~2012-04-02 14:33 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-06 14:59 the maxcpus= boot parameter broke somewhere along the line Jeff Moyer
2012-03-06 15:17 ` Sasha Levin
2012-03-06 16:08 ` Jeff Moyer
2012-03-06 16:48 ` Nick Bowler
2012-03-06 17:15 ` Sasha Levin
2012-03-06 18:08 ` Jeff Moyer
2012-03-07 15:41 ` Srivatsa S. Bhat
2012-03-07 19:14 ` Jeff Moyer
2012-03-09 11:22 ` Srivatsa S. Bhat
2012-04-02 14:05 ` Jeff Moyer
2012-04-02 14:32 ` Srivatsa S. Bhat [this message]
2012-04-02 14:38 ` Jeff Moyer
2012-04-04 7:02 ` Srivatsa S. Bhat
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