linux-kernel - [PATCH 6/6] kernel/locking: Remove unused union members from struct qrwlock

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Date:   Thu,  5 Oct 2017 13:54:57 +0100
From:   Will Deacon <will.deacon@....com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org, Jeremy.Linton@....com,
        peterz@...radead.org, mingo@...hat.com, longman@...hat.com,
        boqun.feng@...il.com, paulmck@...ux.vnet.ibm.com,
        Will Deacon <will.deacon@....com>
Subject: [PATCH 6/6] kernel/locking: Remove unused union members from struct qrwlock

Now that all atomic operations are performed on the full lock word of
the qrwlock, there's no need to define a union type exposing the reader
and writer subcomponents. Remove them.

Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Waiman Long <longman@...hat.com>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Signed-off-by: Will Deacon <will.deacon@....com>
---
 include/asm-generic/qrwlock_types.h | 15 ++-------------
 1 file changed, 2 insertions(+), 13 deletions(-)

diff --git a/include/asm-generic/qrwlock_types.h b/include/asm-generic/qrwlock_types.h
index 507f2dc51bba..7f53be31359c 100644
--- a/include/asm-generic/qrwlock_types.h
+++ b/include/asm-generic/qrwlock_types.h
@@ -9,23 +9,12 @@
  */
 
 typedef struct qrwlock {
-	union {
-		atomic_t cnts;
-		struct {
-#ifdef __LITTLE_ENDIAN
-			u8 wmode;	/* Writer mode   */
-			u8 rcnts[3];	/* Reader counts */
-#else
-			u8 rcnts[3];	/* Reader counts */
-			u8 wmode;	/* Writer mode   */
-#endif
-		};
-	};
+	atomic_t cnts;
 	arch_spinlock_t		wait_lock;
 } arch_rwlock_t;
 
 #define	__ARCH_RW_LOCK_UNLOCKED {		\
-	{ .cnts = ATOMIC_INIT(0), },		\
+	.cnts = ATOMIC_INIT(0),			\
 	.wait_lock = __ARCH_SPIN_LOCK_UNLOCKED,	\
 }
 
-- 
2.1.4