Re: [PATCH 02/17] Make cpu_tsc_khz updates use local CPU.

From: Avi Kivity
Date: Tue Jun 15 2010 - 04:03:00 EST

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:
+ smp_call_function_single(cpu, tsc_khz_changed, NULL, 1);
+ break;
+ 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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