[PATCH v6 5/9] Add timekeeping snapshot code capturing system time and counter
From: Christopher S. Hall <hidden>
Date: 2016-01-13 19:18:46
Also in:
intel-wired-lan, lkml
Subsystem:
the rest, timekeeping, clocksource core, ntp, alarmtimer · Maintainers:
Linus Torvalds, John Stultz, Thomas Gleixner
In the current timekeeping code there isn't any interface to atomically capture the current relationship between the system counter and system time. ktime_get_snapshot() returns this triple (counter, monotonic raw, realtime) in the system_time_snapshot struct. Signed-off-by: Christopher S. Hall <redacted> --- include/linux/clocksource.h | 13 +++++++++++++ include/linux/timekeeping.h | 6 ++++++ kernel/time/timekeeping.c | 31 +++++++++++++++++++++++++++++++ 3 files changed, 50 insertions(+)
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h
index 726ca68..cccbd1c 100644
--- a/include/linux/clocksource.h
+++ b/include/linux/clocksource.h@@ -281,4 +281,17 @@ struct correlated_cs { cycle_t cycles); }; +/* + * struct system_time_snapshot - simultaneous raw/real time capture with + * counter value + * @cycles: Clocksource counter value to produce the system times + * @real: Realtime system time + * @raw: Monotonic raw system time + */ +struct system_time_snapshot { + cycles_t cycles; + ktime_t real; + ktime_t raw; +}; + #endif /* _LINUX_CLOCKSOURCE_H */
diff --git a/include/linux/timekeeping.h b/include/linux/timekeeping.h
index 2651e0a..f5fe657 100644
--- a/include/linux/timekeeping.h
+++ b/include/linux/timekeeping.h@@ -301,6 +301,12 @@ struct sync_device_time_cb { extern int get_device_system_crosststamp(struct sync_device_time_cb *cb, struct system_device_crosststamp *ts); +struct system_time_snapshot; +/* + * Simultaneously snapshot realtime and monotonic raw clocks + */ +extern void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot); + /* * Persistent clock related interfaces */
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
index 84534f8..26049df 100644
--- a/kernel/time/timekeeping.c
+++ b/kernel/time/timekeeping.c@@ -862,6 +862,37 @@ time64_t ktime_get_real_seconds(void) } EXPORT_SYMBOL_GPL(ktime_get_real_seconds); +/** + * ktime_get_snapshot - snapshots the realtime/monotonic raw clocks with counter + * @systime_snapshot: pointer to struct receiving the system time snapshot + */ +void ktime_get_snapshot(struct system_time_snapshot *systime_snapshot) +{ + struct timekeeper *tk = &tk_core.timekeeper; + unsigned long seq; + ktime_t base_raw; + ktime_t base_real; + s64 nsec_raw; + s64 nsec_real; + cycle_t now; + + do { + seq = read_seqcount_begin(&tk_core.seq); + + now = tk->tkr_mono.read(tk->tkr_mono.clock); + base_real = ktime_add(tk->tkr_mono.base, + tk_core.timekeeper.offs_real); + base_raw = tk->tkr_raw.base; + nsec_real = timekeeping_cycles_to_ns(&tk->tkr_mono, now); + nsec_raw = timekeeping_cycles_to_ns(&tk->tkr_raw, now); + } while (read_seqcount_retry(&tk_core.seq, seq)); + + systime_snapshot->cycles = now; + systime_snapshot->real = ktime_add_ns(base_real, nsec_real); + systime_snapshot->raw = ktime_add_ns(base_raw, nsec_raw); +} +EXPORT_SYMBOL_GPL(ktime_get_snapshot); + #ifdef CONFIG_NTP_PPS /**
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2.1.4