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  * (the type definitions are in asm/spinlock_types.h)
  32  */
  33
  34 #define __raw_spin_is_locked(x) ((x)->lock != 0)
  35 #define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
  36 #define __raw_spin_unlock_wait(lock) \
  37         do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
  38
  39 extern void _raw_spin_lock_wait(raw_spinlock_t *lp, unsigned int pc);
  40 extern int _raw_spin_trylock_retry(raw_spinlock_t *lp, unsigned int pc);
  41
  42 static inline void __raw_spin_lock(raw_spinlock_t *lp)
  43 {
  44         unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
  45
  46         if (unlikely(_raw_compare_and_swap(&lp->lock, 0, pc) != 0))
  47                 _raw_spin_lock_wait(lp, pc);
  48 }
  49
  50 static inline int __raw_spin_trylock(raw_spinlock_t *lp)
  51 {
  52         unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
  53
  54         if (likely(_raw_compare_and_swap(&lp->lock, 0, pc) == 0))
  55                 return 1;
  56         return _raw_spin_trylock_retry(lp, pc);
  57 }
  58
  59 static inline void __raw_spin_unlock(raw_spinlock_t *lp)
  60 {
  61         _raw_compare_and_swap(&lp->lock, lp->lock, 0);
  62 }
  63
  64 /*
  65  * Read-write spinlocks, allowing multiple readers
  66  * but only one writer.
  67  *
  68  * NOTE! it is quite common to have readers in interrupts
  69  * but no interrupt writers. For those circumstances we
  70  * can "mix" irq-safe locks - any writer needs to get a
  71  * irq-safe write-lock, but readers can get non-irqsafe
  72  * read-locks.
  73  */
  74
  75 /**
  76  * read_can_lock - would read_trylock() succeed?
  77  * @lock: the rwlock in question.
  78  */
  79 #define __raw_read_can_lock(x) ((int)(x)->lock >= 0)
  80
  81 /**
  82  * write_can_lock - would write_trylock() succeed?
  83  * @lock: the rwlock in question.
  84  */
  85 #define __raw_write_can_lock(x) ((x)->lock == 0)
  86
  87 extern void _raw_read_lock_wait(raw_rwlock_t *lp);
  88 extern int _raw_read_trylock_retry(raw_rwlock_t *lp);
  89 extern void _raw_write_lock_wait(raw_rwlock_t *lp);
  90 extern int _raw_write_trylock_retry(raw_rwlock_t *lp);
  91
  92 static inline void __raw_read_lock(raw_rwlock_t *rw)
  93 {
  94         unsigned int old;
  95         old = rw->lock & 0x7fffffffU;
  96         if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
  97                 _raw_read_lock_wait(rw);
  98 }
  99
 100 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 101 {
 102         unsigned int old, cmp;
 103
 104         old = rw->lock;
 105         do {
 106                 cmp = old;
 107                 old = _raw_compare_and_swap(&rw->lock, old, old - 1);
 108         } while (cmp != old);
 109 }
 110
 111 static inline void __raw_write_lock(raw_rwlock_t *rw)
 112 {
 113         if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
 114                 _raw_write_lock_wait(rw);
 115 }
 116
 117 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 118 {
 119         _raw_compare_and_swap(&rw->lock, 0x80000000, 0);
 120 }
 121
 122 static inline int __raw_read_trylock(raw_rwlock_t *rw)
 123 {
 124         unsigned int old;
 125         old = rw->lock & 0x7fffffffU;
 126         if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
 127                 return 1;
 128         return _raw_read_trylock_retry(rw);
 129 }
 130
 131 static inline int __raw_write_trylock(raw_rwlock_t *rw)
 132 {
 133         if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
 134                 return 1;
 135         return _raw_write_trylock_retry(rw);
 136 }
 137
 138 #endif /* __ASM_SPINLOCK_H */