Allow sched_clock() to be used before schec_clock_init() and sched_clock_init_late() are called. This provides us with a way to get early boot timestamps on machines with unstable clocks.
Signed-off-by: Pavel Tatashin <pasha.tatas...@oracle.com> --- kernel/sched/clock.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index e086babe6c61..8bc603951c2d 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -217,6 +217,11 @@ void clear_sched_clock_stable(void) */ static int __init sched_clock_init_late(void) { + /* Transition to unstable clock from early clock */ + local_irq_disable(); + __gtod_offset = sched_clock() + __sched_clock_offset - ktime_get_ns(); + local_irq_enable(); + sched_clock_running = 2; /* * Ensure that it is impossible to not do a static_key update. @@ -362,8 +367,9 @@ u64 sched_clock_cpu(int cpu) if (sched_clock_stable()) return sched_clock() + __sched_clock_offset; - if (unlikely(!sched_clock_running)) - return 0ull; + /* Use early clock until sched_clock_init_late() */ + if (unlikely(sched_clock_running < 2)) + return sched_clock() + __sched_clock_offset; preempt_disable_notrace(); scd = cpu_sdc(cpu); -- 2.15.0