Subject: sched: fix sched_clock_cpu() From: Peter Zijlstra Make sched_clock_cpu() return 0 before it has been initialized and avoid corrupting its state due to doing so. This fixes the weird printk timestamp jump reported. Signed-off-by: Peter Zijlstra --- kernel/sched_clock.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) Index: linux-2.6/kernel/sched_clock.c =================================================================== --- linux-2.6.orig/kernel/sched_clock.c +++ linux-2.6/kernel/sched_clock.c @@ -59,22 +59,26 @@ static inline struct sched_clock_data *c return &per_cpu(sched_clock_data, cpu); } +static __read_mostly int sched_clock_running; + void sched_clock_init(void) { u64 ktime_now = ktime_to_ns(ktime_get()); - u64 now = 0; + unsigned long now_jiffies = jiffies; int cpu; for_each_possible_cpu(cpu) { struct sched_clock_data *scd = cpu_sdc(cpu); scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; - scd->prev_jiffies = jiffies; - scd->prev_raw = now; - scd->tick_raw = now; + scd->prev_jiffies = now_jiffies; + scd->prev_raw = 0; + scd->tick_raw = 0; scd->tick_gtod = ktime_now; scd->clock = ktime_now; } + + sched_clock_running = 1; } /* @@ -136,6 +140,9 @@ u64 sched_clock_cpu(int cpu) struct sched_clock_data *scd = cpu_sdc(cpu); u64 now, clock; + if (unlikely(!sched_clock_running)) + return 0ull; + WARN_ON_ONCE(!irqs_disabled()); now = sched_clock(); @@ -174,6 +181,9 @@ void sched_clock_tick(void) struct sched_clock_data *scd = this_scd(); u64 now, now_gtod; + if (unlikely(!sched_clock_running)) + return; + WARN_ON_ONCE(!irqs_disabled()); now = sched_clock();