include/asm-s390/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 static inline int
  15 _raw_compare_and_swap(volatile unsigned int *lock,
  16                       unsigned int old, unsigned int new)
  17 {
  18         asm volatile ("cs %0,%3,0(%4)"
  19                       : "=d" (old), "=m" (*lock)
  20                       : "0" (old), "d" (new), "a" (lock), "m" (*lock)
  21                       : "cc", "memory" );
  22         return old;
  23 }
  24
  25 /*
  26  * Simple spin lock operations.  There are two variants, one clears IRQ's
  27  * on the local processor, one does not.
  28  *
  29  * We make no fairness assumptions. They have a cost.
  30  */
  31
  32 typedef struct {
  33         volatile unsigned int lock;
  34 #ifdef CONFIG_PREEMPT
  35         unsigned int break_lock;
  36 #endif
  37 } __attribute__ ((aligned (4))) spinlock_t;
  38
  39 #define SPIN_LOCK_UNLOCKED      (spinlock_t) { 0 }
  40 #define spin_lock_init(lp)      do { (lp)->lock = 0; } while(0)
  41 #define spin_unlock_wait(lp)    do { barrier(); } while(((volatile spinlock_t *)(lp))->lock)
  42 #define spin_is_locked(x)       ((x)->lock != 0)
  43 #define _raw_spin_lock_flags(lock, flags) _raw_spin_lock(lock)
  44
  45 extern void _raw_spin_lock_wait(spinlock_t *lp, unsigned int pc);
  46 extern int _raw_spin_trylock_retry(spinlock_t *lp, unsigned int pc);
  47
  48 static inline void _raw_spin_lock(spinlock_t *lp)
  49 {
  50         unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
  51
  52         if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0))
  53                 _raw_spin_lock_wait(lp, pc);
  54 }
  55
  56 static inline int _raw_spin_trylock(spinlock_t *lp)
  57 {
  58         unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
  59
  60         if (likely(_raw_compare_and_swap(&lp->lock, 0, pc) == 0))
  61                 return 1;
  62         return _raw_spin_trylock_retry(lp, pc);
  63 }
  64
  65 static inline void _raw_spin_unlock(spinlock_t *lp)
  66 {
  67         _raw_compare_and_swap(&lp->lock, lp->lock, 0);
  68 }
  69
  70 /*
  71  * Read-write spinlocks, allowing multiple readers
  72  * but only one writer.
  73  *
  74  * NOTE! it is quite common to have readers in interrupts
  75  * but no interrupt writers. For those circumstances we
  76  * can "mix" irq-safe locks - any writer needs to get a
  77  * irq-safe write-lock, but readers can get non-irqsafe
  78  * read-locks.
  79  */
  80 typedef struct {
  81         volatile unsigned int lock;
  82         volatile unsigned long owner_pc;
  83 #ifdef CONFIG_PREEMPT
  84         unsigned int break_lock;
  85 #endif
  86 } rwlock_t;
  87
  88 #define RW_LOCK_UNLOCKED (rwlock_t) { 0, 0 }
  89
  90 #define rwlock_init(x)  do { *(x) = RW_LOCK_UNLOCKED; } while(0)
  91
  92 /**
  93  * read_can_lock - would read_trylock() succeed?
  94  * @lock: the rwlock in question.
  95  */
  96 #define read_can_lock(x) ((int)(x)->lock >= 0)
  97
  98 /**
  99  * write_can_lock - would write_trylock() succeed?
 100  * @lock: the rwlock in question.
 101  */
 102 #define write_can_lock(x) ((x)->lock == 0)
 103
 104 extern void _raw_read_lock_wait(rwlock_t *lp);
 105 extern int _raw_read_trylock_retry(rwlock_t *lp);
 106 extern void _raw_write_lock_wait(rwlock_t *lp);
 107 extern int _raw_write_trylock_retry(rwlock_t *lp);
 108
 109 static inline void _raw_read_lock(rwlock_t *rw)
 110 {
 111         unsigned int old;
 112         old = rw->lock & 0x7fffffffU;
 113         if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
 114                 _raw_read_lock_wait(rw);
 115 }
 116
 117 static inline void _raw_read_unlock(rwlock_t *rw)
 118 {
 119         unsigned int old, cmp;
 120
 121         old = rw->lock;
 122         do {
 123                 cmp = old;
 124                 old = _raw_compare_and_swap(&rw->lock, old, old - 1);
 125         } while (cmp != old);
 126 }
 127
 128 static inline void _raw_write_lock(rwlock_t *rw)
 129 {
 130         if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
 131                 _raw_write_lock_wait(rw);
 132 }
 133
 134 static inline void _raw_write_unlock(rwlock_t *rw)
 135 {
 136         _raw_compare_and_swap(&rw->lock, 0x80000000, 0);
 137 }
 138
 139 static inline int _raw_read_trylock(rwlock_t *rw)
 140 {
 141         unsigned int old;
 142         old = rw->lock & 0x7fffffffU;
 143         if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
 144                 return 1;
 145         return _raw_read_trylock_retry(rw);
 146 }
 147
 148 static inline int _raw_write_trylock(rwlock_t *rw)
 149 {
 150         if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
 151                 return 1;
 152         return _raw_write_trylock_retry(rw);
 153 }
 154
 155 #endif /* __ASM_SPINLOCK_H */