linux-kernel - [PATCH tip/core/rcu 25/88] srcu: Shrink Tiny SRCU a bit more

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Date:   Thu, 25 May 2017 14:58:58 -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 25/88] srcu: Shrink Tiny SRCU a bit more

This commit rearranges Tiny SRCU's srcu_struct structure, substitutes
u8 for bool, and shrinks counters down to short.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 include/linux/srcutiny.h | 8 ++++----
 kernel/rcu/rcutorture.c  | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
index 42311ee0334f..b8859179b001 100644
--- a/include/linux/srcutiny.h
+++ b/include/linux/srcutiny.h
@@ -27,15 +27,15 @@
 #include <linux/swait.h>
 
 struct srcu_struct {
-	int srcu_lock_nesting[2];	/* srcu_read_lock() nesting depth. */
+	short srcu_lock_nesting[2];	/* srcu_read_lock() nesting depth. */
+	short srcu_idx;			/* Current reader array element. */
+	u8 srcu_gp_running;		/* GP workqueue running? */
+	u8 srcu_gp_waiting;		/* GP waiting for readers? */
 	struct swait_queue_head srcu_wq;
 					/* Last srcu_read_unlock() wakes GP. */
 	unsigned long srcu_gp_seq;	/* GP seq # for callback tagging. */
 	struct rcu_segcblist srcu_cblist;
 					/* Pending SRCU callbacks. */
-	int srcu_idx;			/* Current reader array element. */
-	bool srcu_gp_running;		/* GP workqueue running? */
-	bool srcu_gp_waiting;		/* GP waiting for readers? */
 	struct work_struct srcu_work;	/* For driving grace periods. */
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 	struct lockdep_map dep_map;
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index ae6e574d4cf5..a58592b73f19 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -609,7 +609,7 @@ static void srcu_torture_stats(void)
 	pr_cont("\n");
 #elif defined(CONFIG_TINY_SRCU)
 	idx = READ_ONCE(srcu_ctlp->srcu_idx) & 0x1;
-	pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%d,%d)\n",
+	pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n",
 		 torture_type, TORTURE_FLAG, idx,
 		 READ_ONCE(srcu_ctlp->srcu_lock_nesting[!idx]),
 		 READ_ONCE(srcu_ctlp->srcu_lock_nesting[idx]));
-- 
2.5.2