Messages in this thread Patches in this message | | | From | Arnd Bergmann <> | Subject | Re: [PATCH v5] timekeeping: Added a function to return tv_sec portion of ktime_get_ts64() | Date | Sun, 26 Oct 2014 22:01:28 +0100 |
| |
On Saturday 25 October 2014 17:12:48 Thomas Gleixner wrote: > I'd rather have an extra field in the timekeeper > > u64 xtime_sec; > + u64 ktime_sec; > > and update this in tk_update_ktime_data() so the readout function > boils down to > > time64_t ktime_get_seconds(void) > { > #if BITS_PER_LONG < 64 > u64 sec; > int seq; > > do { > seq = read_seqcount_begin(&tk_core.seq); > sec = tk->ktime_sec; > } while (read_seqcount_retry(&tk_core.seq, seq)); > > return sec; > #else > return tk->ktime_sec; > #endif > } > > So 64bit can do w/o the seqcount and 32bit avoids all extra math, right? >
But where would you set ktime_sec? My first thought was tk_update_ktime_data(), but would then either be slightly wrong because it doesn't take the current xtime_nsec + tk->wall_to_monotonic.tv_nsec into account, if we do
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index ec1791fae965..d72a456c6bd3 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -426,8 +426,8 @@ static inline void tk_update_ktime_data(struct timekeeper *tk) * nsec = base_mono + now(); * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec */ - nsec = (s64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec); - nsec *= NSEC_PER_SEC; + tk->ktime_sec = (s64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec); + nsec = tk->ktime_sec * NSEC_PER_SEC; nsec += tk->wall_to_monotonic.tv_nsec; tk->tkr.base_mono = ns_to_ktime(nsec); or we'd have to add an expensive timekeeping_get_ns() call:
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index ec1791fae965..d4c95b815de6 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -426,9 +426,11 @@ static inline void tk_update_ktime_data(struct timekeeper *tk) * nsec = base_mono + now(); * ==> base_mono = (xtime_sec + wtm_sec) * 1e9 + wtm_nsec */ - nsec = (s64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec); - nsec *= NSEC_PER_SEC; - nsec += tk->wall_to_monotonic.tv_nsec; + tk->ktime_sec = (s64)(tk->xtime_sec + tk->wall_to_monotonic.tv_sec); + nsec = tk->wall_to_monotonic.tv_nsec; + if ((nsec + timekeeping_get_ns()) > NSEC_PER_SEC) + tk->ktime_sec += 1; + nsec += tk->ktime_sec * NSEC_PER_SEC; tk->tkr.base_mono = ns_to_ktime(nsec); /* Update the monotonic raw base */ Arnd
| |