linux-kernel - Re: [Next] CPU Hotplug test failures on powerpc

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Message-ID: <1260947890.8023.1281.camel@laptop>
Date:	Wed, 16 Dec 2009 08:18:10 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Sachin Sant <sachinp@...ibm.com>
Cc:	Xiaotian Feng <xtfeng@...il.com>,
	Linux/PPC Development <linuxppc-dev@...abs.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, linux-next@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [Next] CPU Hotplug test failures on powerpc

On Wed, 2009-12-16 at 12:24 +0530, Sachin Sant wrote:
> Xiaotian Feng wrote:
> > On Wed, Dec 16, 2009 at 2:41 PM, Sachin Sant <sachinp@...ibm.com> wrote:
> >   
> >> Xiaotian Feng wrote:
> >>     
> >>> Does this testcase hotplug cpu 0 off?
> >>>
> >>>       
> >> No, i don't think so. It skips cpu0 during online/offline
> >> process.
> >>     
> >
> > Then how could this happen ? Looks like cpu 0 is offline ....
> > 0:mon> <4>IRQ 17 affinity broken off cpu 0
> > <4>IRQ 18 affinity broken off cpu 0
> > <4>IRQ 19 affinity broken off cpu 0
> > <4>IRQ 264 affinity broken off cpu 0
> > <4>cpu 0 (hwid 0) Ready to die...
> > <7>clockevent: decrementer mult[83126e97] shift[32] cpu[0]
> >   
> Sorry i was looking at only one script. Looking more closely
> at the test there are 6 different sub tests. The rest of the
> tests do seem to hotplug CPU 0.

Ooh, cute, so you can actually hotplug cpu 0.. no wonder that didn't get
exposed on x86.

Still, the only time cpu_active_mask should not be equal to
cpu_online_mask is when we're in the middle of a hotplug, we clear
active early and set it late, but its all done under the hotplug mutex,
so we can at most have 1 cpu differences with online mask.

Unless of course, I messed up, which appears to be rather likely given
these problems ;-)

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