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authorPavel Tatashin <pasha.tatashin@oracle.com>2018-07-19 23:55:42 +0300
committerThomas Gleixner <tglx@linutronix.de>2018-07-20 01:02:43 +0300
commit857baa87b6422bcfb84ed3631d6839920cb5b09d (patch)
treeb63b887069a177a5897821c39f91177173696434
parent5d2a4e91a541cb04d20d11602f0f9340291322ac (diff)
downloadlinux-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.c2
-rw-r--r--kernel/sched/clock.c20
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);