Re: [PATCHv4 15/28] x86/vdso: Add offsets page in vvar

[Dmitry Safonov <0x7f454c46@gmail.com>]

On 6/14/19 2:58 PM, Thomas Gleixner wrote:
> On Wed, 12 Jun 2019, Dmitry Safonov wrote:
>>  
>> +#ifdef CONFIG_TIME_NS
>> +notrace static __always_inline void clk_to_ns(clockid_t clk, struct timespec *ts)
>> +{
>> +	struct timens_offsets *timens = (struct timens_offsets *) &timens_page;
>> +	struct timespec64 *offset64;
>> +
>> +	switch (clk) {
>> +	case CLOCK_MONOTONIC:
>> +	case CLOCK_MONOTONIC_COARSE:
>> +	case CLOCK_MONOTONIC_RAW:
>> +		offset64 = &timens->monotonic;
>> +		break;
>> +	case CLOCK_BOOTTIME:
>> +		offset64 = &timens->boottime;
>> +	default:
>> +		return;
>> +	}
>> +
>> +	ts->tv_nsec += offset64->tv_nsec;
>> +	ts->tv_sec += offset64->tv_sec;
>> +	if (ts->tv_nsec >= NSEC_PER_SEC) {
>> +		ts->tv_nsec -= NSEC_PER_SEC;
>> +		ts->tv_sec++;
>> +	}
>> +	if (ts->tv_nsec < 0) {
>> +		ts->tv_nsec += NSEC_PER_SEC;
>> +		ts->tv_sec--;
>> +	}
> 
> I had to think twice why adding the offset (which can be negative) can
> never result in negative time being returned. A comment explaining this
> would be appreciated.
> 
> As I'm planning to merge Vincezos VDSO consolidation into 5.3, can you
> please start to work on top of his series, which should be available as
> final v7 next week hopefully.

Yes, will rebase on the top of his series.

Thanks much,
          Dmitry