Commit e0d02285 authored by Will Deacon's avatar Will Deacon Committed by Ingo Molnar
Browse files

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: default avatarWill Deacon <will.deacon@arm.com>
Acked-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 5a8897cc

include/asm-generic/qrwlock.h

+1 −11
Original line number Diff line number Diff line
@@ -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);

}



/*

include/asm-generic/qrwlock_types.h

+13 −2
Original line number Diff line number Diff line
@@ -9,12 +9,23 @@ 
 */



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

		};

	};

	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,	\

}

kernel/locking/qrwlock.c

+2 −24
Original line number Diff line number Diff line
@@ -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();

CRA Git | Maintained and supported by SUSTech CRA and CCSE