include/asm-parisc/spinlock.h

   1 #ifndef __ASM_SPINLOCK_H
   2 #define __ASM_SPINLOCK_H
   3
   4 #include <asm/system.h>
   5 #include <asm/processor.h>
   6 #include <asm/spinlock_types.h>
   7
   8 static inline int __raw_spin_is_locked(raw_spinlock_t *x)
   9 {
  10         volatile unsigned int *a = __ldcw_align(x);
  11         return *a == 0;
  12 }
  13
  14 #define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
  15 #define __raw_spin_unlock_wait(x) \
  16                 do { cpu_relax(); } while (__raw_spin_is_locked(x))
  17
  18 static inline void __raw_spin_lock(raw_spinlock_t *x)
  19 {
  20         volatile unsigned int *a;
  21
  22         mb();
  23         a = __ldcw_align(x);
  24         while (__ldcw(a) == 0)
  25                 while (*a == 0);
  26         mb();
  27 }
  28
  29 static inline void __raw_spin_unlock(raw_spinlock_t *x)
  30 {
  31         volatile unsigned int *a;
  32         mb();
  33         a = __ldcw_align(x);
  34         *a = 1;
  35         mb();
  36 }
  37
  38 static inline int __raw_spin_trylock(raw_spinlock_t *x)
  39 {
  40         volatile unsigned int *a;
  41         int ret;
  42
  43         mb();
  44         a = __ldcw_align(x);
  45         ret = __ldcw(a) != 0;
  46         mb();
  47
  48         return ret;
  49 }
  50
  51 /*
  52  * Read-write spinlocks, allowing multiple readers
  53  * but only one writer.
  54  */
  55
  56 #define __raw_read_trylock(lock) generic__raw_read_trylock(lock)
  57
  58 /* read_lock, read_unlock are pretty straightforward.  Of course it somehow
  59  * sucks we end up saving/restoring flags twice for read_lock_irqsave aso. */
  60
  61 static  __inline__ void __raw_read_lock(raw_rwlock_t *rw)
  62 {
  63         unsigned long flags;
  64         local_irq_save(flags);
  65         __raw_spin_lock(&rw->lock);
  66
  67         rw->counter++;
  68
  69         __raw_spin_unlock(&rw->lock);
  70         local_irq_restore(flags);
  71 }
  72
  73 static  __inline__ void __raw_read_unlock(raw_rwlock_t *rw)
  74 {
  75         unsigned long flags;
  76         local_irq_save(flags);
  77         __raw_spin_lock(&rw->lock);
  78
  79         rw->counter--;
  80
  81         __raw_spin_unlock(&rw->lock);
  82         local_irq_restore(flags);
  83 }
  84
  85 /* write_lock is less trivial.  We optimistically grab the lock and check
  86  * if we surprised any readers.  If so we release the lock and wait till
  87  * they're all gone before trying again
  88  *
  89  * Also note that we don't use the _irqsave / _irqrestore suffixes here.
  90  * If we're called with interrupts enabled and we've got readers (or other
  91  * writers) in interrupt handlers someone fucked up and we'd dead-lock
  92  * sooner or later anyway.   prumpf */
  93
  94 static  __inline__ void __raw_write_lock(raw_rwlock_t *rw)
  95 {
  96 retry:
  97         __raw_spin_lock(&rw->lock);
  98
  99         if(rw->counter != 0) {
 100                 /* this basically never happens */
 101                 __raw_spin_unlock(&rw->lock);
 102
 103                 while (rw->counter != 0)
 104                         cpu_relax();
 105
 106                 goto retry;
 107         }
 108
 109         /* got it.  now leave without unlocking */
 110         rw->counter = -1; /* remember we are locked */
 111 }
 112
 113 /* write_unlock is absolutely trivial - we don't have to wait for anything */
 114
 115 static  __inline__ void __raw_write_unlock(raw_rwlock_t *rw)
 116 {
 117         rw->counter = 0;
 118         __raw_spin_unlock(&rw->lock);
 119 }
 120
 121 static  __inline__ int __raw_write_trylock(raw_rwlock_t *rw)
 122 {
 123         __raw_spin_lock(&rw->lock);
 124         if (rw->counter != 0) {
 125                 /* this basically never happens */
 126                 __raw_spin_unlock(&rw->lock);
 127
 128                 return 0;
 129         }
 130
 131         /* got it.  now leave without unlocking */
 132         rw->counter = -1; /* remember we are locked */
 133         return 1;
 134 }
 135
 136 static __inline__ int __raw_is_read_locked(raw_rwlock_t *rw)
 137 {
 138         return rw->counter > 0;
 139 }
 140
 141 static __inline__ int __raw_is_write_locked(raw_rwlock_t *rw)
 142 {
 143         return rw->counter < 0;
 144 }
 145
 146 #endif /* __ASM_SPINLOCK_H */