Messages in this thread | | | Subject | Re: [patch 1/4] x86, mtrr: lock stop machine during MTRR rendezvous sequence | From | Peter Zijlstra <> | Date | Thu, 23 Jun 2011 11:05:05 +0200 |
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On Wed, 2011-06-22 at 15:20 -0700, Suresh Siddha wrote: > +#ifdef CONFIG_SMP > + /* > + * If we are not yet online, then there can be no stop_machine() in > + * parallel. Stop machine ensures this by using get_online_cpus(). > + * > + * If we are online, then we need to prevent a stop_machine() happening > + * in parallel by taking the stop cpus mutex. > + */ > + if (cpu_online(raw_smp_processor_id())) > + mutex_lock(&stop_cpus_mutex); > +#endif
This reads like an optimization, is it really worth-while to not take the mutex in the rare offline case?
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