Messages in this thread | | | Date | Mon, 20 May 2013 14:39:22 +0530 | Subject | Re: NOHZ: WARNING: at arch/x86/kernel/smp.c:123 native_smp_send_reschedule, round 2 | From | Viresh Kumar <> |
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On 20 May 2013 14:26, Michael Wang <wangyun@linux.vnet.ibm.com> wrote: > On 05/20/2013 03:25 PM, Michael Wang wrote: >> Yeah, that's right, I guess the issue is, although the policy->cpus is >> correct at a given time, after get cpu from it, it's possible to be >> changed, unless we disabled preempt or irq, or hotplug before we use it... >> >> Like such issue cases: >> get x from policy->cpus >> DOWN notifier >> change policy->cpus >> do offline x >> send ipi to x >> >> Will that happen?
Sorry I am not sure. :(
I can see mutex being used in cpufreq_governor.c which should take care of race conditions...
> May be we could do some test to confirm it? > > diff --git a/drivers/cpufreq/cpufreq_governor.c > b/drivers/cpufreq/cpufreq_governor.c > index 443442d..449be88 100644 > --- a/drivers/cpufreq/cpufreq_governor.c > +++ b/drivers/cpufreq/cpufreq_governor.c > @@ -26,6 +26,7 @@ > #include <linux/tick.h> > #include <linux/types.h> > #include <linux/workqueue.h> > +#include <linux/cpu.h> > > #include "cpufreq_governor.h" > > @@ -180,8 +181,10 @@ void gov_queue_work(struct dbs_data *dbs_data, > struct cpufreq_policy *policy, > if (!all_cpus) { > __gov_queue_work(smp_processor_id(), dbs_data, delay); > } else { > + get_online_cpus(); > for_each_cpu(i, policy->cpus) > __gov_queue_work(i, dbs_data, delay); > + put_online_cpus(); > } > } > EXPORT_SYMBOL_GPL(gov_queue_work); > > This is supposed to make WARN disappear, if it works, then BINGO :)
Let people test it and then we can talk :)
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