Messages in this thread | | | Date | Tue, 15 Jun 2010 11:02:48 +0300 | From | Avi Kivity <> | Subject | Re: [PATCH 02/17] Make cpu_tsc_khz updates use local CPU. |
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On 06/15/2010 10:34 AM, Zachary Amsden wrote: > This simplifies much of the init code; we can now simply always > call tsc_khz_changed, optionally passing it a new value, or letting > it figure out the existing value (while interrupts are disabled, and > thus, by inference from the rule, not raceful against CPU hotplug or > frequency updates, which will issue IPIs to the local CPU to perform > this very same task). > > > -static void bounce_off(void *info) > +static void tsc_bad(void *info) > { > - /* nothing */ > + per_cpu(cpu_tsc_khz, raw_smp_processor_id()) = 0; >
Can use __get_cpu_var(cpu_tsc_khz) = 0;
> +} > + > +static void tsc_khz_changed(void *data) > +{ > + struct cpufreq_freqs *freq = data; > + > + if (data) { > + per_cpu(cpu_tsc_khz, freq->cpu) = freq->new; > + } else if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) { > + __get_cpu_var(cpu_tsc_khz) = > + cpufreq_quick_get(raw_smp_processor_id()); > + } >
Excessive bracketing.
> + if (!per_cpu(cpu_tsc_khz, raw_smp_processor_id())) > + per_cpu(cpu_tsc_khz, raw_smp_processor_id()) = tsc_khz; > } > > > +static int kvmclock_cpu_notifier(struct notifier_block *nfb, > + unsigned long action, void *hcpu) > +{ > + unsigned int cpu = (unsigned long)hcpu; > + > + switch (action) { > + case CPU_ONLINE: > + case CPU_DOWN_FAILED: > + smp_call_function_single(cpu, tsc_khz_changed, NULL, 1); > + break; > + case CPU_DOWN_PREPARE: > + smp_call_function_single(cpu, tsc_bad, NULL, 1); > + break; >
A little frightening in the chance for livelock, but I think you got it right. vcpus on the doomed cpu will have need_resched() set and will not be trapped in a loop trying to write the clock and failing.
-- error compiling committee.c: too many arguments to function
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