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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_lock_flags(lock, flags) __raw_spin_lock(lock)
  57 #define __raw_spin_unlock_wait(lock) \
  58         do { while (__raw_spin_is_locked(lock)) \
  59                  _raw_spin_relax(lock); } while (0)
  60
  61 extern void _raw_spin_lock_wait(raw_spinlock_t *, unsigned int pc);
  62 extern int _raw_spin_trylock_retry(raw_spinlock_t *, unsigned int pc);
  63 extern void _raw_spin_relax(raw_spinlock_t *lock);
  64
  65 static inline void __raw_spin_lock(raw_spinlock_t *lp)
  66 {
  67         unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
  68         int old;
  69
  70         old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  71         if (likely(old == 0)) {
  72                 lp->owner_pc = pc;
  73                 return;
  74         }
  75         _raw_spin_lock_wait(lp, pc);
  76 }
  77
  78 static inline int __raw_spin_trylock(raw_spinlock_t *lp)
  79 {
  80         unsigned long pc = 1 | (unsigned long) __builtin_return_address(0);
  81         int old;
  82
  83         old = _raw_compare_and_swap(&lp->owner_cpu, 0, ~smp_processor_id());
  84         if (likely(old == 0)) {
  85                 lp->owner_pc = pc;
  86                 return 1;
  87         }
  88         return _raw_spin_trylock_retry(lp, pc);
  89 }
  90
  91 static inline void __raw_spin_unlock(raw_spinlock_t *lp)
  92 {
  93         lp->owner_pc = 0;
  94         _raw_compare_and_swap(&lp->owner_cpu, lp->owner_cpu, 0);
  95 }
  96
  97 /*
  98  * Read-write spinlocks, allowing multiple readers
  99  * but only one writer.
 100  *
 101  * NOTE! it is quite common to have readers in interrupts
 102  * but no interrupt writers. For those circumstances we
 103  * can "mix" irq-safe locks - any writer needs to get a
 104  * irq-safe write-lock, but readers can get non-irqsafe
 105  * read-locks.
 106  */
 107
 108 /**
 109  * read_can_lock - would read_trylock() succeed?
 110  * @lock: the rwlock in question.
 111  */
 112 #define __raw_read_can_lock(x) ((int)(x)->lock >= 0)
 113
 114 /**
 115  * write_can_lock - would write_trylock() succeed?
 116  * @lock: the rwlock in question.
 117  */
 118 #define __raw_write_can_lock(x) ((x)->lock == 0)
 119
 120 extern void _raw_read_lock_wait(raw_rwlock_t *lp);
 121 extern int _raw_read_trylock_retry(raw_rwlock_t *lp);
 122 extern void _raw_write_lock_wait(raw_rwlock_t *lp);
 123 extern int _raw_write_trylock_retry(raw_rwlock_t *lp);
 124
 125 static inline void __raw_read_lock(raw_rwlock_t *rw)
 126 {
 127         unsigned int old;
 128         old = rw->lock & 0x7fffffffU;
 129         if (_raw_compare_and_swap(&rw->lock, old, old + 1) != old)
 130                 _raw_read_lock_wait(rw);
 131 }
 132
 133 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 134 {
 135         unsigned int old, cmp;
 136
 137         old = rw->lock;
 138         do {
 139                 cmp = old;
 140                 old = _raw_compare_and_swap(&rw->lock, old, old - 1);
 141         } while (cmp != old);
 142 }
 143
 144 static inline void __raw_write_lock(raw_rwlock_t *rw)
 145 {
 146         if (unlikely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) != 0))
 147                 _raw_write_lock_wait(rw);
 148 }
 149
 150 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 151 {
 152         _raw_compare_and_swap(&rw->lock, 0x80000000, 0);
 153 }
 154
 155 static inline int __raw_read_trylock(raw_rwlock_t *rw)
 156 {
 157         unsigned int old;
 158         old = rw->lock & 0x7fffffffU;
 159         if (likely(_raw_compare_and_swap(&rw->lock, old, old + 1) == old))
 160                 return 1;
 161         return _raw_read_trylock_retry(rw);
 162 }
 163
 164 static inline int __raw_write_trylock(raw_rwlock_t *rw)
 165 {
 166         if (likely(_raw_compare_and_swap(&rw->lock, 0, 0x80000000) == 0))
 167                 return 1;
 168         return _raw_write_trylock_retry(rw);
 169 }
 170
 171 #define _raw_read_relax(lock)   cpu_relax()
 172 #define _raw_write_relax(lock)  cpu_relax()
 173
 174 #endif /* __ASM_SPINLOCK_H */