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   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 #if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ > 2)
  17
  18 static 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 #else /* __GNUC__ */
  31
  32 static inline int
  33 _raw_compare_and_swap(volatile unsigned int *lock,
  34                       unsigned int old, unsigned int new)
  35 {
  36         asm volatile(
  37                 "       cs      %0,%3,0(%4)"
  38                 : "=d" (old), "=m" (*lock)
  39                 : "0" (old), "d" (new), "a" (lock), "m" (*lock)
  40                 : "cc", "memory" );
  41         return old;
  42 }
  43
  44 #endif /* __GNUC__ */
  45
  46 /*
  47  * Simple spin lock operations.  There are two variants, one clears IRQ's
  48  * on the local processor, one does not.
  49  *
  50  * We make no fairness assumptions. They have a cost.
  51  *
  52  * (the type definitions are in asm/spinlock_types.h)
  53  */
  54
  55 #define __raw_spin_is_locked(x) ((x)->owner_cpu != 0)
  56 #define __raw_spin_unlock_wait(lock) \
  57         do { while (__raw_spin_is_locked(lock)) \
  58                  _raw_spin_relax(lock); } while (0)
  59
  60 extern void _raw_spin_lock_wait(raw_spinlock_t *);
  61 extern void _raw_spin_lock_wait_flags(raw_spinlock_t *, unsigned long flags);
  62 extern int _raw_spin_trylock_retry(raw_spinlock_t *);
  63 extern void _raw_spin_relax(raw_spinlock_t *lock);
  64
  65 static inline void __raw_spin_lock(raw_spinlock_t *lp)
  66 {
  67         int old;
  68
  69         old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  70         if (likely(old == 0))
  71                 return;
  72         _raw_spin_lock_wait(lp);
  73 }
  74
  75 static inline void __raw_spin_lock_flags(raw_spinlock_t *lp,
  76                                          unsigned long flags)
  77 {
  78         int old;
  79
  80         old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  81         if (likely(old == 0))
  82                 return;
  83         _raw_spin_lock_wait_flags(lp, flags);
  84 }
  85
  86 static inline int __raw_spin_trylock(raw_spinlock_t *lp)
  87 {
  88         int old;
  89
  90         old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  91         if (likely(old == 0))
  92                 return 1;
  93         return _raw_spin_trylock_retry(lp);
  94 }
  95
  96 static inline void __raw_spin_unlock(raw_spinlock_t *lp)
  97 {
  98         _raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0);
  99 }
 100
 101 /*
 102  * Read-write spinlocks, allowing multiple readers
 103  * but only one writer.
 104  *
 105  * NOTE! it is quite common to have readers in interrupts
 106  * but no interrupt writers. For those circumstances we
 107  * can "mix" irq-safe locks - any writer needs to get a
 108  * irq-safe write-lock, but readers can get non-irqsafe
 109  * read-locks.
 110  */
 111
 112 /**
 113  * read_can_lock - would read_trylock() succeed?
 114  * @lock: the rwlock in question.
 115  */
 116 #define __raw_read_can_lock(x) ((int)(x)->lock >= 0)
 117
 118 /**
 119  * write_can_lock - would write_trylock() succeed?
 120  * @lock: the rwlock in question.
 121  */
 122 #define __raw_write_can_lock(x) ((x)->lock == 0)
 123
 124 extern void _raw_read_lock_wait(raw_rwlock_t *lp);
 125 extern int _raw_read_trylock_retry(raw_rwlock_t *lp);
 126 extern void _raw_write_lock_wait(raw_rwlock_t *lp);
 127 extern int _raw_write_trylock_retry(raw_rwlock_t *lp);
 128
 129 static inline void __raw_read_lock(raw_rwlock_t *rw)
 130 {
 131         unsigned int old;
 132         old = rw->lock & 0x7fffffffU;
 133         if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
 134                 _raw_read_lock_wait(rw);
 135 }
 136
 137 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 138 {
 139         unsigned int old, cmp;
 140
 141         old = rw->lock;
 142         do {
 143                 cmp = old;
 144                 old = _raw_compare_and_swap(&rw->lock, old, old - 1);
 145         } while (cmp != old);
 146 }
 147
 148 static inline void __raw_write_lock(raw_rwlock_t *rw)
 149 {
 150         if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
 151                 _raw_write_lock_wait(rw);
 152 }
 153
 154 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 155 {
 156         _raw_compare_and_swap(&rw->lock, 0x80000000, 0);
 157 }
 158
 159 static inline int __raw_read_trylock(raw_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
 168 static inline int __raw_write_trylock(raw_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 _raw_read_relax(lock)   cpu_relax()
 176 #define _raw_write_relax(lock)  cpu_relax()
 177
 178 #endif /* __ASM_SPINLOCK_H */