Messages in this thread | | | Date | Thu, 30 Nov 2006 12:03:15 +0100 | From | Ingo Molnar <> | Subject | Re: CPUFREQ-CPUHOTPLUG: Possible circular locking dependency |
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* Gautham R Shenoy <ego@in.ibm.com> wrote:
> a) cpufreq maintain's it's own cpumask in the variable > policy->affected_cpus and says : If a frequency change is issued to > any one of the cpu's in the affected_cpus mask, you change frequency > on all cpus in the mask. So this needs to be consistent with > cpu_online map and hence cpu hotplug aware. Furthermore, we don't want > cpus in this mask to go down when we are trying to change frequencies > on them. The function which drives the frequency change in > cpufreq-core is cpufreq_driver_target and it needs cpu-hotplug > protection.
couldnt this complexity be radically simplified by having new kernel infrastructure that does something like:
" 'gather' all CPUs mentioned in <mask> via scheduling a separate helper-kthread on every CPU that <mask> specifies, disable all interrupts, and execute function <fn> once all CPUs have been 'gathered' - and release all CPUs once <fn> has executed on each of them."
?
This would be done totally serialized and while holding the hotplug lock, so no CPU could go away or arrive while this operation is going on.
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