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Commit 46457ea4 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Thomas Gleixner
Browse files

sched/clock: Use static key for sched_clock_running 



sched_clock_running may be read every time sched_clock_cpu() is called.
Yet, this variable is updated only twice during boot, and never changes
again, therefore it is better to make it a static key.

Signed-off-by: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
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: 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/20180719205545.16512-25-pasha.tatashin@oracle.com
parent 857baa87

kernel/sched/clock.c

+8 −8
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ unsigned long long __weak sched_clock(void) 
}

EXPORT_SYMBOL_GPL(sched_clock);



__read_mostly int sched_clock_running;

static DEFINE_STATIC_KEY_FALSE(sched_clock_running);



#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK

/*
@@ -191,7 +191,7 @@ void clear_sched_clock_stable(void) 


	smp_mb(); /* matches sched_clock_init_late() */



	if (sched_clock_running == 2)

	if (static_key_count(&sched_clock_running.key) == 2)

		__clear_sched_clock_stable();

}
@@ -215,7 +215,7 @@ void __init sched_clock_init(void) 
	__sched_clock_gtod_offset();

	local_irq_restore(flags);



	sched_clock_running = 1;

	static_branch_inc(&sched_clock_running);



	/* Now that sched_clock_running is set adjust scd */

	local_irq_save(flags);
@@ -228,7 +228,7 @@ void __init sched_clock_init(void) 
 */

static int __init sched_clock_init_late(void)

{

	sched_clock_running = 2;

	static_branch_inc(&sched_clock_running);

	/*

	 * Ensure that it is impossible to not do a static_key update.

	 *
@@ -373,7 +373,7 @@ u64 sched_clock_cpu(int cpu) 
	if (sched_clock_stable())

		return sched_clock() + __sched_clock_offset;



	if (unlikely(!sched_clock_running))

	if (!static_branch_unlikely(&sched_clock_running))

		return sched_clock();



	preempt_disable_notrace();
@@ -396,7 +396,7 @@ void sched_clock_tick(void) 
	if (sched_clock_stable())

		return;



	if (unlikely(!sched_clock_running))

	if (!static_branch_unlikely(&sched_clock_running))

		return;



	lockdep_assert_irqs_disabled();
@@ -455,13 +455,13 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); 


void __init sched_clock_init(void)

{

	sched_clock_running = 1;

	static_branch_inc(&sched_clock_running);

	generic_sched_clock_init();

}



u64 sched_clock_cpu(int cpu)

{

	if (unlikely(!sched_clock_running))

	if (!static_branch_unlikely(&sched_clock_running))

		return 0;



	return sched_clock();

kernel/sched/debug.c

+0 −2
Original line number Diff line number Diff line
@@ -623,8 +623,6 @@ void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq) 
#undef PU

}



extern __read_mostly int sched_clock_running;



static void print_cpu(struct seq_file *m, int cpu)

{

	struct rq *rq = cpu_rq(cpu);