locking/qrwlock: Use 'struct qrwlock' instead of 'struct __qrwlock'

There's no good reason to keep the internal structure of struct qrwlock hidden from qrwlock.h, particularly as it's actually needed for unlock and ends up being abstracted independently behind the __qrwlock_write_byte() function. Stop pretending we can hide this stuff, and move the __qrwlock definition into qrwlock, removing the __qrwlock_write_byte() nastiness and using the same struct definition everywhere instead. Signed-off-by: Will Deacon <[email protected]> Acked-by: Peter Zijlstra <[email protected]> Cc: Boqun Feng <[email protected]> Cc: [email protected] Cc: Linus Torvalds <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Waiman Long <[email protected]> Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]>
chewitt · Oct 25, 2017 · e0d0228 · e0d0228
1 parent 5a8897c
commit e0d0228
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Showing 3 changed files with 16 additions and 37 deletions.
diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
@@ -128,23 +128,13 @@ static inline void queued_read_unlock(struct qrwlock *lock)
 	(void)atomic_sub_return_release(_QR_BIAS, &lock->cnts);
 }
 
-/**
- * __qrwlock_write_byte - retrieve the write byte address of a queue rwlock
- * @lock : Pointer to queue rwlock structure
- * Return: the write byte address of a queue rwlock
- */
-static inline u8 *__qrwlock_write_byte(struct qrwlock *lock)
-{
-	return (u8 *)lock + 3 * IS_BUILTIN(CONFIG_CPU_BIG_ENDIAN);
-}
-
 /**
  * queued_write_unlock - release write lock of a queue rwlock
  * @lock : Pointer to queue rwlock structure
  */
 static inline void queued_write_unlock(struct qrwlock *lock)
 {
-	smp_store_release(__qrwlock_write_byte(lock), 0);
+	smp_store_release(&lock->wmode, 0);
 }
 
 /*

diff --git a/include/asm-generic/qrwlock_types.h b/include/asm-generic/qrwlock_types.h
@@ -9,12 +9,23 @@
  */
 
 typedef struct qrwlock {
-	atomic_t		cnts;
+	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
+		};
+	};
 	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,	\
 }
 

diff --git a/kernel/locking/qrwlock.c b/kernel/locking/qrwlock.c
@@ -23,26 +23,6 @@
 #include <linux/spinlock.h>
 #include <asm/qrwlock.h>
 
-/*
- * This internal data structure is used for optimizing access to some of
- * the subfields within the atomic_t cnts.
- */
-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
-		};
-	};
-	arch_spinlock_t	lock;
-};
-
 /**
  * rspin_until_writer_unlock - inc reader count & spin until writer is gone
  * @lock  : Pointer to queue rwlock structure
@@ -125,10 +105,8 @@ void queued_write_lock_slowpath(struct qrwlock *lock)
 	 * or wait for a previous writer to go away.
 	 */
 	for (;;) {
-		struct __qrwlock *l = (struct __qrwlock *)lock;
-
-		if (!READ_ONCE(l->wmode) &&
-		   (cmpxchg_relaxed(&l->wmode, 0, _QW_WAITING) == 0))
+		if (!READ_ONCE(lock->wmode) &&
+		   (cmpxchg_relaxed(&lock->wmode, 0, _QW_WAITING) == 0))
 			break;
 
 		cpu_relax();