linux-kernel - [PATCH tip/core/rcu 40/88] srcu: Shrink Tiny SRCU a bit

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Date:   Thu, 25 May 2017 14:59:13 -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 40/88] srcu: Shrink Tiny SRCU a bit

In Tiny SRCU, __srcu_read_lock() is a trivial function, outweighed by
its EXPORT_SYMBOL_GPL(), and on many architectures, its call sequence.
This commit therefore moves it to srcutiny.h so that it can be inlined.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 include/linux/srcutiny.h | 14 ++++++++++++++
 kernel/rcu/srcutiny.c    | 15 ---------------
 2 files changed, 14 insertions(+), 15 deletions(-)

diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index b8859179b001..013b1b30a354 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -63,6 +63,20 @@ void srcu_drive_gp(struct work_struct *wp);
 
 void synchronize_srcu(struct srcu_struct *sp);
 
+/*
+ * Counts the new reader in the appropriate per-CPU element of the
+ * srcu_struct.  Must be called from process context.
+ * Returns an index that must be passed to the matching srcu_read_unlock().
+ */
+static inline int __srcu_read_lock(struct srcu_struct *sp)
+{
+	int idx;
+
+	idx = READ_ONCE(sp->srcu_idx);
+	WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1);
+	return idx;
+}
+
 static inline void synchronize_srcu_expedited(struct srcu_struct *sp)
 {
 	synchronize_srcu(sp);
diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 36e1f82faed1..fe0b16db2aae 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -96,21 +96,6 @@ void cleanup_srcu_struct(struct srcu_struct *sp)
 EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
 
 /*
- * Counts the new reader in the appropriate per-CPU element of the
- * srcu_struct.  Must be called from process context.
- * Returns an index that must be passed to the matching srcu_read_unlock().
- */
-int __srcu_read_lock(struct srcu_struct *sp)
-{
-	int idx;
-
-	idx = READ_ONCE(sp->srcu_idx);
-	WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1);
-	return idx;
-}
-EXPORT_SYMBOL_GPL(__srcu_read_lock);
-
-/*
  * Removes the count for the old reader from the appropriate element of
  * the srcu_struct.  Must be called from process context.
  */
-- 
2.5.2