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 <will.deacon@arm.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>
Cc: Jeremy.Linton@arm.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Waiman Long <longman@redhat.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1507810851-306-2-git-send-email-will.deacon@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/include/asm-generic/qrwlock.h b/include/asm-generic/qrwlock.h
index 50925327b0a8374a8698b05d4278ff42fc551428..02c0a768e6b085296a81af52e6f0e0dfbe7801a6 100644 (file)
--- 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
index 0abc6b6062fbb1c203bed0f025e05e82ac3eea24..507f2dc51bba98f6f3d3d0f93f58940af9ece784 100644 (file)
--- 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
index 2655f26ec882689f42d2ba7831209f166ce45869..1af791e3734893789682b8eed1b9cdf0c2ae10da 100644 (file)
--- 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();