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| author | Pavel Tatashin <pasha.tatashin@oracle.com> | 2018-07-19 23:55:42 +0300 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2018-07-20 01:02:43 +0300 |
| commit | 857baa87b6422bcfb84ed3631d6839920cb5b09d (patch) | |
| tree | b63b887069a177a5897821c39f91177173696434 | |
| parent | 5d2a4e91a541cb04d20d11602f0f9340291322ac (diff) | |
| download | linux-857baa87b6422bcfb84ed3631d6839920cb5b09d.tar.xz | |
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 <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: steven.sistare@oracle.com
Cc: daniel.m.jordan@oracle.com
Cc: linux@armlinux.org.uk
Cc: schwidefsky@de.ibm.com
Cc: heiko.carstens@de.ibm.com
Cc: john.stultz@linaro.org
Cc: sboyd@codeaurora.org
Cc: hpa@zytor.com
Cc: douly.fnst@cn.fujitsu.com
Cc: peterz@infradead.org
Cc: prarit@redhat.com
Cc: feng.tang@intel.com
Cc: pmladek@suse.com
Cc: gnomes@lxorguk.ukuu.org.uk
Cc: linux-s390@vger.kernel.org
Cc: boris.ostrovsky@oracle.com
Cc: jgross@suse.com
Cc: pbonzini@redhat.com
Link: https://lkml.kernel.org/r/20180719205545.16512-24-pasha.tatashin@oracle.com
| -rw-r--r-- | init/main.c | 2 | ||||
| -rw-r--r-- | 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); |