Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: Missing CLOCK_BOOTTIME_RAW? | Date | Mon, 18 May 2020 15:01:25 +0200 |
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Pali Rohár <pali@kernel.org> writes: > On Monday 18 May 2020 14:13:48 Thomas Gleixner wrote: >> Of course not, but the kernel relies on that application behaving >> sanely. If it does not then the time stamps you are complaining about >> are the least of your worries. > > I do not thing it is too bad... When I needed to deal in userspace with > time/date/clock I just needed either "current time in UTC" to show it to > user (possible in different timezone and pretty formatted) or I needed > "timestamp since some epoch" suitable for measuring time differences. > > For first case I used CLOCK_REALTIME and for second case I used > CLOCK_MONOTONIC_RAW (as it was not affected by adjtime()). > > And I would like to know, it is correct to use these two clocks in those > situations?
It's your choice to do so. I prefer CLOCK_MONOTONIC simply because it's in human understandable units and not some assumed frequency.
> Anyway, what would happen with CLOCK_BOOTTIME when during suspend is > that external RTC source shifted back? Is kernel guarantee that > CLOCK_BOOTTIME is always monotonic even in this case?
If the RTC delta is negative, then it's ignored, i.e. 0 sleep time injected.
Thanks,
tglx
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