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Commit 22ab8bc0 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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nohz: Allow to check if remote CPU tick is stopped 



This check is racy but provides a good heuristic to determine whether
a CPU may need a remote tick or not.

Signed-off-by: default avatarFrederic Weisbecker <frederic@kernel.org>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Wanpeng Li <kernellwp@gmail.com>
Link: http://lkml.kernel.org/r/1519186649-3242-4-git-send-email-frederic@kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a3642983

include/linux/tick.h

+2 −0
Original line number Diff line number Diff line
@@ -114,6 +114,7 @@ enum tick_dep_bits { 
#ifdef CONFIG_NO_HZ_COMMON

extern bool tick_nohz_enabled;

extern bool tick_nohz_tick_stopped(void);

extern bool tick_nohz_tick_stopped_cpu(int cpu);

extern void tick_nohz_idle_enter(void);

extern void tick_nohz_idle_exit(void);

extern void tick_nohz_irq_exit(void);
@@ -125,6 +126,7 @@ extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time); 
#else /* !CONFIG_NO_HZ_COMMON */

#define tick_nohz_enabled (0)

static inline int tick_nohz_tick_stopped(void) { return 0; }

static inline int tick_nohz_tick_stopped_cpu(int cpu) { return 0; }

static inline void tick_nohz_idle_enter(void) { }

static inline void tick_nohz_idle_exit(void) { }

kernel/time/tick-sched.c

+7 −0
Original line number Diff line number Diff line
@@ -486,6 +486,13 @@ bool tick_nohz_tick_stopped(void) 
	return __this_cpu_read(tick_cpu_sched.tick_stopped);

}



bool tick_nohz_tick_stopped_cpu(int cpu)

{

	struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);



	return ts->tick_stopped;

}



/**

 * tick_nohz_update_jiffies - update jiffies when idle was interrupted

 *