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