s390: use generic rwsem implementation

generic-y += mcs_spinlock.h

generic-y += mm-arch-hooks.h

generic-y += preempt.h

generic-y += rwsem.h

generic-y += trace_clock.h

generic-y += unaligned.h

generic-y += word-at-a-time.h

#ifndef _S390_RWSEM_H

#define _S390_RWSEM_H

/*

 *  S390 version

 *    Copyright IBM Corp. 2002

 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)

 *

 *  Based on asm-alpha/semaphore.h and asm-i386/rwsem.h

 */

/*

 *

 * The MSW of the count is the negated number of active writers and waiting

 * lockers, and the LSW is the total number of active locks

 *

 * The lock count is initialized to 0 (no active and no waiting lockers).

 *

 * When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an

 * uncontended lock. This can be determined because XADD returns the old value.

 * Readers increment by 1 and see a positive value when uncontended, negative

 * if there are writers (and maybe) readers waiting (in which case it goes to

 * sleep).

 *

 * The value of WAITING_BIAS supports up to 32766 waiting processes. This can

 * be extended to 65534 by manually checking the whole MSW rather than relying

 * on the S flag.

 *

 * The value of ACTIVE_BIAS supports up to 65535 active processes.

 *

 * This should be totally fair - if anything is waiting, a process that wants a

 * lock will go to the back of the queue. When the currently active lock is

 * released, if there's a writer at the front of the queue, then that and only

 * that will be woken up; if there's a bunch of consecutive readers at the

 * front, then they'll all be woken up, but no other readers will be.

 */

#ifndef _LINUX_RWSEM_H

#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"

#endif

#define RWSEM_UNLOCKED_VALUE	0x0000000000000000L

#define RWSEM_ACTIVE_BIAS	0x0000000000000001L

#define RWSEM_ACTIVE_MASK	0x00000000ffffffffL

#define RWSEM_WAITING_BIAS	(-0x0000000100000000L)

#define RWSEM_ACTIVE_READ_BIAS	RWSEM_ACTIVE_BIAS

#define RWSEM_ACTIVE_WRITE_BIAS	(RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)

/*

 * lock for reading

 */

static inline void __down_read(struct rw_semaphore *sem)

{

	signed long old, new;

	asm volatile(

		"	lg	%0,%2\n"

		"0:	lgr	%1,%0\n"

		"	aghi	%1,%4\n"

		"	csg	%0,%1,%2\n"

		"	jl	0b"

		: "=&d" (old), "=&d" (new), "=Q" (sem->count)

		: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)

		: "cc", "memory");

	if (old < 0)

		rwsem_down_read_failed(sem);

}

/*

 * trylock for reading -- returns 1 if successful, 0 if contention

 */

static inline int __down_read_trylock(struct rw_semaphore *sem)

{

	signed long old, new;

	asm volatile(

		"	lg	%0,%2\n"

		"0:	ltgr	%1,%0\n"

		"	jm	1f\n"

		"	aghi	%1,%4\n"

		"	csg	%0,%1,%2\n"

		"	jl	0b\n"

		"1:"

		: "=&d" (old), "=&d" (new), "=Q" (sem->count)

		: "Q" (sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)

		: "cc", "memory");

	return old >= 0 ? 1 : 0;

}

/*

 * lock for writing

 */

static inline long ___down_write(struct rw_semaphore *sem)

{

	signed long old, new, tmp;

	tmp = RWSEM_ACTIVE_WRITE_BIAS;

	asm volatile(

		"	lg	%0,%2\n"

		"0:	lgr	%1,%0\n"

		"	ag	%1,%4\n"

		"	csg	%0,%1,%2\n"

		"	jl	0b"

		: "=&d" (old), "=&d" (new), "=Q" (sem->count)

		: "Q" (sem->count), "m" (tmp)

		: "cc", "memory");

	return old;

}

static inline void __down_write(struct rw_semaphore *sem)

{

	if (___down_write(sem))

		rwsem_down_write_failed(sem);

}

static inline int __down_write_killable(struct rw_semaphore *sem)

{

	if (___down_write(sem))

		if (IS_ERR(rwsem_down_write_failed_killable(sem)))

			return -EINTR;

	return 0;

}

/*

 * trylock for writing -- returns 1 if successful, 0 if contention

 */

static inline int __down_write_trylock(struct rw_semaphore *sem)

{

	signed long old;

	asm volatile(

		"	lg	%0,%1\n"

		"0:	ltgr	%0,%0\n"

		"	jnz	1f\n"

		"	csg	%0,%3,%1\n"

		"	jl	0b\n"

		"1:"

		: "=&d" (old), "=Q" (sem->count)

		: "Q" (sem->count), "d" (RWSEM_ACTIVE_WRITE_BIAS)

		: "cc", "memory");

	return (old == RWSEM_UNLOCKED_VALUE) ? 1 : 0;

}

/*

 * unlock after reading

 */

static inline void __up_read(struct rw_semaphore *sem)

{

	signed long old, new;

	asm volatile(

		"	lg	%0,%2\n"

		"0:	lgr	%1,%0\n"

		"	aghi	%1,%4\n"

		"	csg	%0,%1,%2\n"

		"	jl	0b"

		: "=&d" (old), "=&d" (new), "=Q" (sem->count)

		: "Q" (sem->count), "i" (-RWSEM_ACTIVE_READ_BIAS)

		: "cc", "memory");

	if (new < 0)

		if ((new & RWSEM_ACTIVE_MASK) == 0)

			rwsem_wake(sem);

}

/*

 * unlock after writing

 */

static inline void __up_write(struct rw_semaphore *sem)

{

	signed long old, new, tmp;

	tmp = -RWSEM_ACTIVE_WRITE_BIAS;

	asm volatile(

		"	lg	%0,%2\n"

		"0:	lgr	%1,%0\n"

		"	ag	%1,%4\n"

		"	csg	%0,%1,%2\n"

		"	jl	0b"

		: "=&d" (old), "=&d" (new), "=Q" (sem->count)

		: "Q" (sem->count), "m" (tmp)

		: "cc", "memory");

	if (new < 0)

		if ((new & RWSEM_ACTIVE_MASK) == 0)

			rwsem_wake(sem);

}

/*

 * downgrade write lock to read lock

 */

static inline void __downgrade_write(struct rw_semaphore *sem)

{

	signed long old, new, tmp;

	tmp = -RWSEM_WAITING_BIAS;

	asm volatile(

		"	lg	%0,%2\n"

		"0:	lgr	%1,%0\n"

		"	ag	%1,%4\n"

		"	csg	%0,%1,%2\n"

		"	jl	0b"

		: "=&d" (old), "=&d" (new), "=Q" (sem->count)

		: "Q" (sem->count), "m" (tmp)

		: "cc", "memory");

	if (new > 1)

		rwsem_downgrade_wake(sem);

}

#endif /* _S390_RWSEM_H */