[PATCH] rcu: remove rcu_is_idle_cpu

[Yipeng Zou <zouyipeng@huawei.com>]

The commit "x86/cpu: Avoid cpuinfo-induced IPIing of idle CPUs" introduce
this function to identify the current CPU idle state.
But after commit "x86/aperfmperf: Replace arch_freq_get_on_cpu()" we
just use MAX_SAMPLE_AGE to do that, So there is no use of this function.

Fixes: f3eca381bd49 ("x86/aperfmperf: Replace arch_freq_get_on_cpu()")
Signed-off-by: Yipeng Zou <zouyipeng@huawei.com>
---
 include/linux/rcutiny.h | 2 --
 include/linux/rcutree.h | 2 --
 kernel/rcu/tree.c       | 6 ------
 3 files changed, 10 deletions(-)

diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index 9bc025aa79a3..5c271bf3a1e7 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -146,8 +146,6 @@ static inline void rcu_virt_note_context_switch(void) { }
 static inline void rcu_cpu_stall_reset(void) { }
 static inline int rcu_jiffies_till_stall_check(void) { return 21 * HZ; }
 static inline void rcu_irq_exit_check_preempt(void) { }
-#define rcu_is_idle_cpu(cpu) \
-	(is_idle_task(current) && !in_nmi() && !in_hardirq() && !in_serving_softirq())
 static inline void exit_rcu(void) { }
 static inline bool rcu_preempt_need_deferred_qs(struct task_struct *t)
 {
diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 70795386b9ff..4003bf6cfa1c 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -87,8 +87,6 @@ bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
 void cond_synchronize_rcu(unsigned long oldstate);
 void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp);
 
-bool rcu_is_idle_cpu(int cpu);
-
 #ifdef CONFIG_PROVE_RCU
 void rcu_irq_exit_check_preempt(void);
 #else
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5ec97e3f7468..f6561aa401c0 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -301,12 +301,6 @@ static bool rcu_dynticks_in_eqs(int snap)
 	return !(snap & RCU_DYNTICKS_IDX);
 }
 
-/* Return true if the specified CPU is currently idle from an RCU viewpoint.  */
-bool rcu_is_idle_cpu(int cpu)
-{
-	return rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu));
-}
-
 /*
  * Return true if the CPU corresponding to the specified rcu_data
  * structure has spent some time in an extended quiescent state since
-- 
2.17.1