arch/s390/include/asm/spinlock.h

   1 /*
   2  *  S390 version
   3  *    Copyright IBM Corp. 1999
   4  *    Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
   5  *
   6  *  Derived from "include/asm-i386/spinlock.h"
   7  */
   8
   9 #ifndef __ASM_SPINLOCK_H
  10 #define __ASM_SPINLOCK_H
  11
  12 #include <linux/smp.h>
  13
  14 #define SPINLOCK_LOCKVAL (S390_lowcore.spinlock_lockval)
  15
  16 extern int spin_retry;
  17
  18 static inline int
  19 _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
  20 {
  21         unsigned int old_expected = old;
  22
  23         asm volatile(
  24                 "       cs      %0,%3,%1"
  25                 : "=d" (old), "=Q" (*lock)
  26                 : "0" (old), "d" (new), "Q" (*lock)
  27                 : "cc", "memory" );
  28         return old == old_expected;
  29 }
  30
  31 /*
  32  * Simple spin lock operations.  There are two variants, one clears IRQ's
  33  * on the local processor, one does not.
  34  *
  35  * We make no fairness assumptions. They have a cost.
  36  *
  37  * (the type definitions are in asm/spinlock_types.h)
  38  */
  39
  40 void arch_lock_relax(unsigned int cpu);
  41
  42 void arch_spin_lock_wait(arch_spinlock_t *);
  43 int arch_spin_trylock_retry(arch_spinlock_t *);
  44 void arch_spin_lock_wait_flags(arch_spinlock_t *, unsigned long flags);
  45
  46 static inline void arch_spin_relax(arch_spinlock_t *lock)
  47 {
  48         arch_lock_relax(lock->lock);
  49 }
  50
  51 static inline u32 arch_spin_lockval(int cpu)
  52 {
  53         return ~cpu;
  54 }
  55
  56 static inline int arch_spin_value_unlocked(arch_spinlock_t lock)
  57 {
  58         return lock.lock == 0;
  59 }
  60
  61 static inline int arch_spin_is_locked(arch_spinlock_t *lp)
  62 {
  63         return ACCESS_ONCE(lp->lock) != 0;
  64 }
  65
  66 static inline int arch_spin_trylock_once(arch_spinlock_t *lp)
  67 {
  68         barrier();
  69         return likely(arch_spin_value_unlocked(*lp) &&
  70                       _raw_compare_and_swap(&lp->lock, 0, SPINLOCK_LOCKVAL));
  71 }
  72
  73 static inline void arch_spin_lock(arch_spinlock_t *lp)
  74 {
  75         if (!arch_spin_trylock_once(lp))
  76                 arch_spin_lock_wait(lp);
  77 }
  78
  79 static inline void arch_spin_lock_flags(arch_spinlock_t *lp,
  80                                         unsigned long flags)
  81 {
  82         if (!arch_spin_trylock_once(lp))
  83                 arch_spin_lock_wait_flags(lp, flags);
  84 }
  85
  86 static inline int arch_spin_trylock(arch_spinlock_t *lp)
  87 {
  88         if (!arch_spin_trylock_once(lp))
  89                 return arch_spin_trylock_retry(lp);
  90         return 1;
  91 }
  92
  93 static inline void arch_spin_unlock(arch_spinlock_t *lp)
  94 {
  95         typecheck(unsigned int, lp->lock);
  96         asm volatile(
  97                 __ASM_BARRIER
  98                 "st     %1,%0\n"
  99                 : "+Q" (lp->lock)
 100                 : "d" (0)
 101                 : "cc", "memory");
 102 }
 103
 104 static inline void arch_spin_unlock_wait(arch_spinlock_t *lock)
 105 {
 106         while (arch_spin_is_locked(lock))
 107                 arch_spin_relax(lock);
 108 }
 109
 110 /*
 111  * Read-write spinlocks, allowing multiple readers
 112  * but only one writer.
 113  *
 114  * NOTE! it is quite common to have readers in interrupts
 115  * but no interrupt writers. For those circumstances we
 116  * can "mix" irq-safe locks - any writer needs to get a
 117  * irq-safe write-lock, but readers can get non-irqsafe
 118  * read-locks.
 119  */
 120
 121 /**
 122  * read_can_lock - would read_trylock() succeed?
 123  * @lock: the rwlock in question.
 124  */
 125 #define arch_read_can_lock(x) ((int)(x)->lock >= 0)
 126
 127 /**
 128  * write_can_lock - would write_trylock() succeed?
 129  * @lock: the rwlock in question.
 130  */
 131 #define arch_write_can_lock(x) ((x)->lock == 0)
 132
 133 extern void _raw_read_lock_wait(arch_rwlock_t *lp);
 134 extern void _raw_write_lock_wait(arch_rwlock_t *lp);
 135 extern int _raw_read_trylock_retry(arch_rwlock_t *lp);
 136 extern int _raw_write_trylock_retry(arch_rwlock_t *lp);
 137
 138 #define arch_read_lock_flags(lock, flags) arch_read_lock(lock)
 139 #define arch_write_lock_flags(lock, flags) arch_write_lock(lock)
 140
 141 static inline int arch_read_trylock_once(arch_rwlock_t *rw)
 142 {
 143         unsigned int old = ACCESS_ONCE(rw->lock);
 144         return likely((int) old >= 0 &&
 145                       _raw_compare_and_swap(&rw->lock, old, old + 1));
 146 }
 147
 148 static inline int arch_write_trylock_once(arch_rwlock_t *rw)
 149 {
 150         unsigned int old = ACCESS_ONCE(rw->lock);
 151         return likely(old == 0 &&
 152                       _raw_compare_and_swap(&rw->lock, 0, 0x80000000));
 153 }
 154
 155 static inline void arch_read_lock(arch_rwlock_t *rw)
 156 {
 157         if (!arch_read_trylock_once(rw))
 158                 _raw_read_lock_wait(rw);
 159 }
 160
 161 static inline void arch_read_unlock(arch_rwlock_t *rw)
 162 {
 163         unsigned int old;
 164
 165         do {
 166                 old = ACCESS_ONCE(rw->lock);
 167         } while (!_raw_compare_and_swap(&rw->lock, old, old - 1));
 168 }
 169
 170 static inline void arch_write_lock(arch_rwlock_t *rw)
 171 {
 172         if (!arch_write_trylock_once(rw))
 173                 _raw_write_lock_wait(rw);
 174         rw->owner = SPINLOCK_LOCKVAL;
 175 }
 176
 177 static inline void arch_write_unlock(arch_rwlock_t *rw)
 178 {
 179         typecheck(unsigned int, rw->lock);
 180
 181         rw->owner = 0;
 182         asm volatile(
 183                 __ASM_BARRIER
 184                 "st     %1,%0\n"
 185                 : "+Q" (rw->lock)
 186                 : "d" (0)
 187                 : "cc", "memory");
 188 }
 189
 190 static inline int arch_read_trylock(arch_rwlock_t *rw)
 191 {
 192         if (!arch_read_trylock_once(rw))
 193                 return _raw_read_trylock_retry(rw);
 194         return 1;
 195 }
 196
 197 static inline int arch_write_trylock(arch_rwlock_t *rw)
 198 {
 199         if (!arch_write_trylock_once(rw) && !_raw_write_trylock_retry(rw))
 200                 return 0;
 201         rw->owner = SPINLOCK_LOCKVAL;
 202         return 1;
 203 }
 204
 205 static inline void arch_read_relax(arch_rwlock_t *rw)
 206 {
 207         arch_lock_relax(rw->owner);
 208 }
 209
 210 static inline void arch_write_relax(arch_rwlock_t *rw)
 211 {
 212         arch_lock_relax(rw->owner);
 213 }
 214
 215 #endif /* __ASM_SPINLOCK_H */