From 3fcd6a230fa7d03bffcb831a81b40435c146c12b Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@kernel.org>
Date: Thu, 3 Sep 2020 15:23:29 -0700
Subject: x86/cpu: Avoid cpuinfo-induced IPIing of idle CPUs

Currently, accessing /proc/cpuinfo sends IPIs to idle CPUs in order to
learn their clock frequency.  Which is a bit strange, given that waking
them from idle likely significantly changes their clock frequency.
This commit therefore avoids sending /proc/cpuinfo-induced IPIs to
idle CPUs.

[ paulmck: Also check for idle in arch_freq_prepare_all(). ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: <x86@kernel.org>
---
 include/linux/rcutree.h | 1 +
 1 file changed, 1 insertion(+)

(limited to 'include/linux/rcutree.h')

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 59eb5cd567d7..df578b73960f 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -50,6 +50,7 @@ void rcu_irq_exit(void);
 void rcu_irq_exit_preempt(void);
 void rcu_irq_enter_irqson(void);
 void rcu_irq_exit_irqson(void);
+bool rcu_is_idle_cpu(int cpu);
 
 #ifdef CONFIG_PROVE_RCU
 void rcu_irq_exit_check_preempt(void);
-- 
cgit