Messages in this thread | | | Date | Fri, 26 Nov 2010 13:17:34 +0100 | From | Heiko Carstens <> | Subject | Re: [patch 3/3] nohz/s390: fix arch_needs_cpu() return value on offline cpus |
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On Fri, Nov 26, 2010 at 01:14:07PM +0100, Peter Zijlstra wrote: > On Fri, 2010-11-26 at 13:01 +0100, Heiko Carstens wrote: > > plain text document attachment (003_arch_needs_cpu.diff) > > From: Heiko Carstens <heiko.carstens@de.ibm.com> > > > > This fixes the same problem as described in the patch "nohz: fix > > printk_needs_cpu() return value on offline cpus" for the arch_needs_cpu() > > primitive. > > This specific bug was indrocuded with 3c5d92a0 "nohz: Introduce arch_needs_cpu". > > > > In this case a cpu hotplug notifier is used to fix the issue in order to keep > > the normal/fast path small. All we need to do is to clear the condition that > > makes arch_needs_cpu() return 1 since it is just a performance improvement which > > is supposed to keep the local tick running for a short period if a cpu goes > > idle. Nothing special needs to be done except for clearing the condition. > > > > Cc: stable@kernel.org > > Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> > > OK, and s390 seems to be the only architecture making use of that > interface. > > Did you audit all the other *_needs_cpu() interfaces for this same > problem?
There's only rcu_needs_cpu() left and rcu indeed has a cpu hotplug notifier. So there _shouldn't_ be any problems with that.
> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> > > Will you take this through the s390?
Yes. Thanks!
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