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#ifndef _S390_RWSEM_H

#define _S390_RWSEM_H

/*

 *  include/asm-s390/rwsem.h

 *

 *  S390 version

 *    Copyright (C) 2002 IBM Deutschland Entwicklung GmbH, IBM Corporation

 *    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 consequtive readers at the

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

 */

#ifndef _LINUX_RWSEM_H

#error please dont include asm/rwsem.h directly, use linux/rwsem.h instead

#endif

#ifdef __KERNEL__

#include <linux/list.h>

#include <linux/spinlock.h>

struct rwsem_waiter;

extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);

extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);

extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);

/*

 * the semaphore definition

 */

struct rw_semaphore {

        signed long             count;

        spinlock_t              wait_lock;

        struct list_head        wait_list;

};

#define RWSEM_UNLOCKED_VALUE    0x00000000

#define RWSEM_ACTIVE_BIAS       0x00000001

#define RWSEM_ACTIVE_MASK       0x0000ffff

#define RWSEM_WAITING_BIAS      (-0x00010000)

#define RWSEM_ACTIVE_READ_BIAS  RWSEM_ACTIVE_BIAS

#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)

/*

 * initialisation

 */

#define __RWSEM_INITIALIZER(name) \

{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) }

#define DECLARE_RWSEM(name) \

        struct rw_semaphore name = __RWSEM_INITIALIZER(name)

static inline void init_rwsem(struct rw_semaphore *sem)

{

        sem->count = RWSEM_UNLOCKED_VALUE;

        spin_lock_init(&sem->wait_lock);

        INIT_LIST_HEAD(&sem->wait_list);

}

/*

 * lock for reading

 */

static inline void __down_read(struct rw_semaphore *sem)

{

        signed long old, new;

        __asm__ __volatile__(

                "   l    %0,0(%2)\n"

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

                "   ahi  %1,%3\n"

                "   cs   %0,%1,0(%2)\n"

                "   jl   0b"

                : "=&d" (old), "=&d" (new)

                : "a" (&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__(

                "   l    %0,0(%2)\n"

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

                "   jm   1f\n"

                "   ahi  %1,%3\n"

                "   cs   %0,%1,0(%2)\n"

                "   jl   0b\n"

                "1:"

                : "=&d" (old), "=&d" (new)

                : "a" (&sem->count), "i" (RWSEM_ACTIVE_READ_BIAS)

                : "cc", "memory" );

        return old >= 0 ? 1 : 0;

}

/*

 * lock for writing

 */

static inline void __down_write(struct rw_semaphore *sem)

{

        signed long old, new, tmp;

        tmp = RWSEM_ACTIVE_WRITE_BIAS;

        __asm__ __volatile__(

                "   l    %0,0(%2)\n"

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

                "   a    %1,%3\n"

                "   cs   %0,%1,0(%2)\n"

                "   jl   0b"

                : "=&d" (old), "=&d" (new)

                : "a" (&sem->count), "m" (tmp)

                : "cc", "memory" );

        if (old != 0)

                rwsem_down_write_failed(sem);

}

/*

 * 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__(

                "   l    %0,0(%1)\n"

                "0: ltr  %0,%0\n"

                "   jnz  1f\n"

                "   cs   %0,%2,0(%1)\n"

                "   jl   0b\n"

                "1:"

                : "=&d" (old)

                : "a" (&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__(

                "   l    %0,0(%2)\n"

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

                "   ahi  %1,%3\n"

                "   cs   %0,%1,0(%2)\n"

                "   jl   0b"

                : "=&d" (old), "=&d" (new)

                : "a" (&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__(

                "   l    %0,0(%2)\n"

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

                "   a    %1,%3\n"

                "   cs   %0,%1,0(%2)\n"

                "   jl   0b"

                : "=&d" (old), "=&d" (new)

                : "a" (&sem->count), "m" (tmp)

                : "cc", "memory" );

        if (new < 0)

                if ((new & RWSEM_ACTIVE_MASK) == 0)

                        rwsem_wake(sem);

}

/*

 * implement atomic add functionality

 */

static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)

{

        signed long old, new;

        __asm__ __volatile__(

                "   l    %0,0(%2)\n"

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

                "   ar   %1,%3\n"

                "   cs   %0,%1,0(%2)\n"

                "   jl   0b"

                : "=&d" (old), "=&d" (new)

                : "a" (&sem->count), "d" (delta)

                : "cc", "memory" );

}

/*

 * implement exchange and add functionality

 */

static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)

{

        signed long old, new;

        __asm__ __volatile__(

                "   l    %0,0(%2)\n"

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

                "   ar   %1,%3\n"

                "   cs   %0,%1,0(%2)\n"

                "   jl   0b"

                : "=&d" (old), "=&d" (new)

                : "a" (&sem->count), "d" (delta)

                : "cc", "memory" );

        return new;

}

#endif /* __KERNEL__ */

#endif /* _S390_RWSEM_H */