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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: Pavel Tatashin <pasha.tatashin@oracle.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter 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
This commit is contained in:
Pavel Tatashin 2018-07-19 16:55:43 -04:00 committed by Thomas Gleixner
parent 857baa87b6
commit 46457ea464
2 changed files with 8 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
kernel/sched/clock.c
View File

@ -67,7 +67,7 @@ unsigned long long __weak sched_clock(void)
} }
EXPORT_SYMBOL_GPL(sched_clock); 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 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
/* /*
@ -191,7 +191,7 @@ void clear_sched_clock_stable(void)
smp_mb(); /* matches sched_clock_init_late() */ 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(); __clear_sched_clock_stable();
} }
@ -215,7 +215,7 @@ void __init sched_clock_init(void)
__sched_clock_gtod_offset(); __sched_clock_gtod_offset();
local_irq_restore(flags); local_irq_restore(flags);
sched_clock_running = 1; static_branch_inc(&sched_clock_running);
/* Now that sched_clock_running is set adjust scd */ /* Now that sched_clock_running is set adjust scd */
local_irq_save(flags); local_irq_save(flags);
@ -228,7 +228,7 @@ void __init sched_clock_init(void)
*/ */
static int __init sched_clock_init_late(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. * 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()) if (sched_clock_stable())
return sched_clock() + __sched_clock_offset; return sched_clock() + __sched_clock_offset;
if (unlikely(!sched_clock_running)) if (!static_branch_unlikely(&sched_clock_running))
return sched_clock(); return sched_clock();
preempt_disable_notrace(); preempt_disable_notrace();
@ -396,7 +396,7 @@ void sched_clock_tick(void)
if (sched_clock_stable()) if (sched_clock_stable())
return; return;
if (unlikely(!sched_clock_running)) if (!static_branch_unlikely(&sched_clock_running))
return; return;
lockdep_assert_irqs_disabled(); lockdep_assert_irqs_disabled();
@ -455,13 +455,13 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
void __init sched_clock_init(void) void __init sched_clock_init(void)
{ {
sched_clock_running = 1; static_branch_inc(&sched_clock_running);
generic_sched_clock_init(); generic_sched_clock_init();
} }
u64 sched_clock_cpu(int cpu) u64 sched_clock_cpu(int cpu)
{ {
if (unlikely(!sched_clock_running)) if (!static_branch_unlikely(&sched_clock_running))
return 0; return 0;
return sched_clock(); return sched_clock();

2
kernel/sched/debug.c
View File

@ -623,8 +623,6 @@ void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq)
#undef PU #undef PU
} }
extern __read_mostly int sched_clock_running;
static void print_cpu(struct seq_file *m, int cpu) static void print_cpu(struct seq_file *m, int cpu)
{ {
struct rq *rq = cpu_rq(cpu); struct rq *rq = cpu_rq(cpu);