On 27/11/17 12:43, Arnd Bergmann wrote:
getnstimeofday() is deprecated, so I'm converting this to use ktime_get_real_ts64() as a safe replacement. I considered using ktime_get_real() instead, but since the algorithm here depends on the exact timing, I decided to introduce fewer changes and leave the code that determines the nanoseconds since the last seconds wrap untouched.
It's not entirely clear to me whether we should also change the time base to CLOCK_BOOTTIME or CLOCK_TAI. With boottime, we would be independent of changes due to settimeofday() and only see the speed adjustment from the upstream clock source, with the downside of having the signal be at an arbirary offset from the start of the UTC second signal. With CLOCK_TAI, we would use the same offset from the UTC second as before and still suffer from settimeofday() adjustments, but would be less confused during leap seconds.
Both boottime and tai only offer usable (i.e. avoiding ktime_t to timespec64 conversion) interfaces for ktime_t though, so either way, changing it wouldn't take significantly more work. CLOCK_MONOTONIC could be used with ktime_get_ts64(), but would lose synchronization across a suspend/resume cycle, which seems worse.
Signed-off-by: Arnd Bergmann email@example.com
Acked-by: Rodolfo Giometti firstname.lastname@example.org