linux-kernel - [PATCH tip/core/rcu 55/88] rcu: Eliminate the unused __rcu_is

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Date:   Thu, 25 May 2017 14:59:28 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 55/88] rcu: Eliminate the unused __rcu_is_watching() function

The __rcu_is_watching() function is currently not used, aside from
to implement the rcu_is_watching() function.  This commit therefore
eliminates __rcu_is_watching(), which has the beneficial side-effect
of shrinking include/linux/rcupdate.h a bit.

Reported-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 include/linux/rcupdate.h |  4 ----
 include/linux/rcutiny.h  | 11 -----------
 kernel/rcu/tiny.c        | 13 -------------
 kernel/rcu/tree.c        | 19 ++++---------------
 4 files changed, 4 insertions(+), 43 deletions(-)

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 415633076cb1..b4edfe0966c6 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -204,10 +204,6 @@ do { \
 		rcu_note_voluntary_context_switch(current); \
 } while (0)
 
-#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP)
-bool __rcu_is_watching(void);
-#endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP) */
-
 /*
  * Infrastructure to implement the synchronize_() primitives in
  * TREE_RCU and rcu_barrier_() primitives in TINY_RCU.
diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h
index ade360e0d58c..5ed6934152a6 100644
--- a/include/linux/rcutiny.h
+++ b/include/linux/rcutiny.h
@@ -232,22 +232,11 @@ static inline void rcu_scheduler_starting(void)
 }
 #endif /* #else #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) */
 
-#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE)
-
-static inline bool rcu_is_watching(void)
-{
-	return __rcu_is_watching();
-}
-
-#else /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
-
 static inline bool rcu_is_watching(void)
 {
 	return true;
 }
 
-#endif /* #else defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
-
 static inline void rcu_request_urgent_qs_task(struct task_struct *t)
 {
 }
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index e5385731e391..2306cab2195d 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -59,19 +59,6 @@ void rcu_barrier_sched(void)
 }
 EXPORT_SYMBOL(rcu_barrier_sched);
 
-#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE)
-
-/*
- * Test whether RCU thinks that the current CPU is idle.
- */
-bool notrace __rcu_is_watching(void)
-{
-	return true;
-}
-EXPORT_SYMBOL(__rcu_is_watching);
-
-#endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */
-
 /*
  * Helper function for rcu_sched_qs() and rcu_bh_qs().
  * Also irqs are disabled to avoid confusion due to interrupt handlers
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 5ebc830297c1..61a97164abcc 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1139,22 +1139,11 @@ void rcu_nmi_exit(void)
 }
 
 /**
- * __rcu_is_watching - are RCU read-side critical sections safe?
- *
- * Return true if RCU is watching the running CPU, which means that
- * this CPU can safely enter RCU read-side critical sections.  Unlike
- * rcu_is_watching(), the caller of __rcu_is_watching() must have at
- * least disabled preemption.
- */
-bool notrace __rcu_is_watching(void)
-{
-	return !rcu_dynticks_curr_cpu_in_eqs();
-}
-
-/**
  * rcu_is_watching - see if RCU thinks that the current CPU is idle
  *
- * If the current CPU is in its idle loop and is neither in an interrupt
+ * Return true if RCU is watching the running CPU, which means that this
+ * CPU can safely enter RCU read-side critical sections.  In other words,
+ * if the current CPU is in its idle loop and is neither in an interrupt
  * or NMI handler, return true.
  */
 bool notrace rcu_is_watching(void)
@@ -1162,7 +1151,7 @@ bool notrace rcu_is_watching(void)
 	bool ret;
 
 	preempt_disable_notrace();
-	ret = __rcu_is_watching();
+	ret = !rcu_dynticks_curr_cpu_in_eqs();
 	preempt_enable_notrace();
 	return ret;
 }
-- 
2.5.2