Commit-ID: 857baa87b6422bcfb84ed3631d6839920cb5b09d Gitweb: https://git.kernel.org/tip/857baa87b6422bcfb84ed3631d6839920cb5b09d Author: Pavel Tatashin <[email protected]> AuthorDate: Thu, 19 Jul 2018 16:55:42 -0400 Committer: Thomas Gleixner <[email protected]> CommitDate: Fri, 20 Jul 2018 00:02:43 +0200
sched/clock: Enable sched clock early Allow sched_clock() to be used before schec_clock_init() is called. This provides a way to get early boot timestamps on machines with unstable clocks. Signed-off-by: Pavel Tatashin <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: https://lkml.kernel.org/r/[email protected] --- init/main.c | 2 +- kernel/sched/clock.c | 20 +++++++++++++++++++- 2 files changed, 20 insertions(+), 2 deletions(-) diff --git a/init/main.c b/init/main.c index 162d931c9511..ff0a24170b95 100644 --- a/init/main.c +++ b/init/main.c @@ -642,7 +642,6 @@ asmlinkage __visible void __init start_kernel(void) softirq_init(); timekeeping_init(); time_init(); - sched_clock_init(); printk_safe_init(); perf_event_init(); profile_init(); @@ -697,6 +696,7 @@ asmlinkage __visible void __init start_kernel(void) acpi_early_init(); if (late_time_init) late_time_init(); + sched_clock_init(); calibrate_delay(); pid_idr_init(); anon_vma_init(); diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index 0e9dbb2d9aea..422cd63f8f17 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -202,7 +202,25 @@ static void __sched_clock_gtod_offset(void) void __init sched_clock_init(void) { + unsigned long flags; + + /* + * Set __gtod_offset such that once we mark sched_clock_running, + * sched_clock_tick() continues where sched_clock() left off. + * + * Even if TSC is buggered, we're still UP at this point so it + * can't really be out of sync. + */ + local_irq_save(flags); + __sched_clock_gtod_offset(); + local_irq_restore(flags); + sched_clock_running = 1; + + /* Now that sched_clock_running is set adjust scd */ + local_irq_save(flags); + sched_clock_tick(); + local_irq_restore(flags); } /* * We run this as late_initcall() such that it runs after all built-in drivers, @@ -356,7 +374,7 @@ u64 sched_clock_cpu(int cpu) return sched_clock() + __sched_clock_offset; if (unlikely(!sched_clock_running)) - return 0ull; + return sched_clock(); preempt_disable_notrace(); scd = cpu_sdc(cpu);
