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SubjectRe: [PATCH v5 08/12] x86/ioapic: Refactor the delay logic in timer_irq_works()
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Hi Thomas,

At 07/03/2017 03:15 AM, Thomas Gleixner wrote:
> On Fri, 30 Jun 2017, Dou Liyang wrote:
>> +static void __init delay_with_tsc(void)
>> +{
>> + unsigned long long start, now;
>> + unsigned long ticks = jiffies;
>
> Please make that
>
> unsigned long end = jiffies + 4;
>
> ticks really means: number of ticks. But that variable is doing something
> different.

um, I see. Will use 'end' instead.

>
>> + start = rdtsc();
>> +
>> + /*
>> + * We don't know the TSC frequency yet, but waiting for
>> + * 40000000000/HZ TSC cycles is safe:
>> + * 4 GHz == 10 jiffies
>> + * 1 GHz == 40 jiffies
>> + */
>> + do {
>> + rep_nop();
>> + now = rdtsc();
>> + } while ((now - start) < 40000000000UL / HZ &&
>> + time_before_eq(jiffies, ticks + 4));
>> +}
>> +
>> +static void __init delay_without_tsc(void)
>> +{
>> + int band = 1;
>> + unsigned long ticks = jiffies;
>
> Please sort variables in reverse fir tree order
>
> unsigned long end = jiffies + 4;
> int band = 1;
>

OK, I will.

>> +
>> + /*
>> + * We don't know any frequency yet, but waiting for
>> + * 40940000000/HZ cycles is safe:
>> + * 4 GHz == 10 jiffies
>> + * 1 GHz == 40 jiffies
>> + * 1 << 1 + 1 << 2 +...+ 1 << 11 = 4094
>> + */
>> + do {
>> + __delay(((1 << band++) * 10000000UL) / HZ);
>
> s/1/1U/
>

Got it!

Thanks,

dou.


>> + } while (band < 12 && time_before_eq(jiffies, ticks + 4));
>> +}
>
> Thanks,
>
> tglx
>
>
>


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