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Commit 857baa87 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Thomas Gleixner
Browse files

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: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: default avatarThomas 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
parent 5d2a4e91

init/main.c

+1 −1
Original line number Diff line number Diff line
@@ -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();

kernel/sched/clock.c

+19 −1
Original line number Diff line number Diff line
@@ -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);