diff options
Diffstat (limited to 'kernel/sched_clock.c')
| -rw-r--r-- | kernel/sched_clock.c | 33 |
1 files changed, 21 insertions, 12 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index 857a1291fd23..074edc989379 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -149,7 +149,7 @@ static void lock_double_clock(struct sched_clock_data *data1, u64 sched_clock_cpu(int cpu) { struct sched_clock_data *scd = cpu_sdc(cpu); - u64 now, clock; + u64 now, clock, this_clock, remote_clock; if (unlikely(!sched_clock_running)) return 0ull; @@ -158,26 +158,36 @@ u64 sched_clock_cpu(int cpu) now = sched_clock(); if (cpu != raw_smp_processor_id()) { - /* - * in order to update a remote cpu's clock based on our - * unstable raw time rebase it against: - * tick_raw (offset between raw counters) - * tick_gotd (tick offset between cpus) - */ struct sched_clock_data *my_scd = this_scd(); lock_double_clock(scd, my_scd); - now += scd->tick_raw - my_scd->tick_raw; - now += my_scd->tick_gtod - scd->tick_gtod; + this_clock = __update_sched_clock(my_scd, now); + remote_clock = scd->clock; + + /* + * Use the opportunity that we have both locks + * taken to couple the two clocks: we take the + * larger time as the latest time for both + * runqueues. (this creates monotonic movement) + */ + if (likely(remote_clock < this_clock)) { + clock = this_clock; + scd->clock = clock; + } else { + /* + * Should be rare, but possible: + */ + clock = remote_clock; + my_scd->clock = remote_clock; + } __raw_spin_unlock(&my_scd->lock); } else { __raw_spin_lock(&scd->lock); + clock = __update_sched_clock(scd, now); } - clock = __update_sched_clock(scd, now); - __raw_spin_unlock(&scd->lock); return clock; @@ -223,7 +233,6 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); void sched_clock_idle_wakeup_event(u64 delta_ns) { struct sched_clock_data *scd = this_scd(); - u64 now = sched_clock(); /* * Override the previous timestamp and ignore all |