LXR linux/arch/s390/include/asm/spinlock.h

   1/*
   2 *  include/asm-s390/spinlock.h
   3 *
   4 *  S390 version
   5 *    Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
   6 *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
   7 *
   8 *  Derived from "include/asm-i386/spinlock.h"
   9 */
  10
  11#ifndef __ASM_SPINLOCK_H
  12#define __ASM_SPINLOCK_H
  13
  14#include <linux/smp.h>
  15
  16extern int spin_retry;
  17
  18static inline int
  19_raw_compare_and_swap(volatile unsigned int *lock,
  20                      unsigned int old, unsigned int new)
  21{
  22        asm volatile(
  23                "       cs      %0,%3,%1"
  24                : "=d" (old), "=Q" (*lock)
  25                : "0" (old), "d" (new), "Q" (*lock)
  26                : "cc", "memory" );
  27        return old;
  28}
  29
  30/*
  31 * Simple spin lock operations.  There are two variants, one clears IRQ's
  32 * on the local processor, one does not.
  33 *
  34 * We make no fairness assumptions. They have a cost.
  35 *
  36 * (the type definitions are in asm/spinlock_types.h)
  37 */
  38
  39#define arch_spin_is_locked(x) ((x)->owner_cpu != 0)
  40#define arch_spin_unlock_wait(lock) \
  41        do { while (arch_spin_is_locked(lock)) \
  42                 arch_spin_relax(lock); } while (0)
  43
  44extern void arch_spin_lock_wait(arch_spinlock_t *);
  45extern void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);
  46extern int arch_spin_trylock_retry(arch_spinlock_t *);
  47extern void arch_spin_relax(arch_spinlock_t *lock);
  48
  49static inline void arch_spin_lock(arch_spinlock_t *lp)
  50{
  51        int old;
  52
  53        old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  54        if (likely(old == 0))
  55                return;
  56        arch_spin_lock_wait(lp);
  57}
  58
  59static inline void arch_spin_lock_flags(arch_spinlock_t *lp,
  60                                         unsigned long flags)
  61{
  62        int old;
  63
  64        old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  65        if (likely(old == 0))
  66                return;
  67        arch_spin_lock_wait_flags(lp, flags);
  68}
  69
  70static inline int arch_spin_trylock(arch_spinlock_t *lp)
  71{
  72        int old;
  73
  74        old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  75        if (likely(old == 0))
  76                return 1;
  77        return arch_spin_trylock_retry(lp);
  78}
  79
  80static inline void arch_spin_unlock(arch_spinlock_t *lp)
  81{
  82        _raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0);
  83}
  84                
  85/*
  86 * Read-write spinlocks, allowing multiple readers
  87 * but only one writer.
  88 *
  89 * NOTE! it is quite common to have readers in interrupts
  90 * but no interrupt writers. For those circumstances we
  91 * can "mix" irq-safe locks - any writer needs to get a
  92 * irq-safe write-lock, but readers can get non-irqsafe
  93 * read-locks.
  94 */
  95
  96/**
  97 * read_can_lock - would read_trylock() succeed?
  98 * @lock: the rwlock in question.
  99 */
 100#define arch_read_can_lock(x) ((int)(x)->lock >= 0)
 101
 102/**
 103 * write_can_lock - would write_trylock() succeed?
 104 * @lock: the rwlock in question.
 105 */
 106#define arch_write_can_lock(x) ((x)->lock == 0)
 107
 108extern void _raw_read_lock_wait(arch_rwlock_t *lp);
 109extern void _raw_read_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags);
 110extern int _raw_read_trylock_retry(arch_rwlock_t *lp);
 111extern void _raw_write_lock_wait(arch_rwlock_t *lp);
 112extern void _raw_write_lock_wait_flags(arch_rwlock_t *lp, unsigned long flags);
 113extern int _raw_write_trylock_retry(arch_rwlock_t *lp);
 114
 115static inline void arch_read_lock(arch_rwlock_t *rw)
 116{
 117        unsigned int old;
 118        old = rw->lock & 0x7fffffffU;
 119        if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
 120                _raw_read_lock_wait(rw);
 121}
 122
 123static inline void arch_read_lock_flags(arch_rwlock_t *rw, unsigned long flags)
 124{
 125        unsigned int old;
 126        old = rw->lock & 0x7fffffffU;
 127        if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
 128                _raw_read_lock_wait_flags(rw, flags);
 129}
 130
 131static inline void arch_read_unlock(arch_rwlock_t *rw)
 132{
 133        unsigned int old, cmp;
 134
 135        old = rw->lock;
 136        do {
 137                cmp = old;
 138                old = _raw_compare_and_swap(&rw->lock, old, old - 1);
 139        } while (cmp != old);
 140}
 141
 142static inline void arch_write_lock(arch_rwlock_t *rw)
 143{
 144        if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
 145                _raw_write_lock_wait(rw);
 146}
 147
 148static inline void arch_write_lock_flags(arch_rwlock_t *rw, unsigned long flags)
 149{
 150        if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
 151                _raw_write_lock_wait_flags(rw, flags);
 152}
 153
 154static inline void arch_write_unlock(arch_rwlock_t *rw)
 155{
 156        _raw_compare_and_swap(&rw->lock, 0x80000000, 0);
 157}
 158
 159static inline int arch_read_trylock(arch_rwlock_t *rw)
 160{
 161        unsigned int old;
 162        old = rw->lock & 0x7fffffffU;
 163        if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
 164                return 1;
 165        return _raw_read_trylock_retry(rw);
 166}
 167
 168static inline int arch_write_trylock(arch_rwlock_t *rw)
 169{
 170        if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
 171                return 1;
 172        return _raw_write_trylock_retry(rw);
 173}
 174
 175#define arch_read_relax(lock)   cpu_relax()
 176#define arch_write_relax(lock)  cpu_relax()
 177
 178#endif /* __ASM_SPINLOCK_H */
 179