arch/sparc/include/asm/spinlock_32.h

   1 /* spinlock.h: 32-bit Sparc spinlock support.
   2  *
   3  * Copyright (C) 1997 David S. Miller (davem@caip.rutgers.edu)
   4  */
   5
   6 #ifndef __SPARC_SPINLOCK_H
   7 #define __SPARC_SPINLOCK_H
   8
   9 #ifndef __ASSEMBLY__
  10
  11 #include <asm/psr.h>
  12
  13 #define arch_spin_is_locked(lock) (*((volatile unsigned char *)(lock)) != 0)
  14
  15 #define arch_spin_unlock_wait(lock) \
  16         do { while (arch_spin_is_locked(lock)) cpu_relax(); } while (0)
  17
  18 static inline void arch_spin_lock(arch_spinlock_t *lock)
  19 {
  20         __asm__ __volatile__(
  21         "\n1:\n\t"
  22         "ldstub [%0], %%g2\n\t"
  23         "orcc   %%g2, 0x0, %%g0\n\t"
  24         "bne,a  2f\n\t"
  25         " ldub  [%0], %%g2\n\t"
  26         ".subsection    2\n"
  27         "2:\n\t"
  28         "orcc   %%g2, 0x0, %%g0\n\t"
  29         "bne,a  2b\n\t"
  30         " ldub  [%0], %%g2\n\t"
  31         "b,a    1b\n\t"
  32         ".previous\n"
  33         : /* no outputs */
  34         : "r" (lock)
  35         : "g2", "memory", "cc");
  36 }
  37
  38 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  39 {
  40         unsigned int result;
  41         __asm__ __volatile__("ldstub [%1], %0"
  42                              : "=r" (result)
  43                              : "r" (lock)
  44                              : "memory");
  45         return (result == 0);
  46 }
  47
  48 static inline void arch_spin_unlock(arch_spinlock_t *lock)
  49 {
  50         __asm__ __volatile__("stb %%g0, [%0]" : : "r" (lock) : "memory");
  51 }
  52
  53 /* Read-write spinlocks, allowing multiple readers
  54  * but only one writer.
  55  *
  56  * NOTE! it is quite common to have readers in interrupts
  57  * but no interrupt writers. For those circumstances we
  58  * can "mix" irq-safe locks - any writer needs to get a
  59  * irq-safe write-lock, but readers can get non-irqsafe
  60  * read-locks.
  61  *
  62  * XXX This might create some problems with my dual spinlock
  63  * XXX scheme, deadlocks etc. -DaveM
  64  *
  65  * Sort of like atomic_t's on Sparc, but even more clever.
  66  *
  67  *      ------------------------------------
  68  *      | 24-bit counter           | wlock |  arch_rwlock_t
  69  *      ------------------------------------
  70  *       31                       8 7     0
  71  *
  72  * wlock signifies the one writer is in or somebody is updating
  73  * counter. For a writer, if he successfully acquires the wlock,
  74  * but counter is non-zero, he has to release the lock and wait,
  75  * till both counter and wlock are zero.
  76  *
  77  * Unfortunately this scheme limits us to ~16,000,000 cpus.
  78  */
  79 static inline void __arch_read_lock(arch_rwlock_t *rw)
  80 {
  81         register arch_rwlock_t *lp asm("g1");
  82         lp = rw;
  83         __asm__ __volatile__(
  84         "mov    %%o7, %%g4\n\t"
  85         "call   ___rw_read_enter\n\t"
  86         " ldstub        [%%g1 + 3], %%g2\n"
  87         : /* no outputs */
  88         : "r" (lp)
  89         : "g2", "g4", "memory", "cc");
  90 }
  91
  92 #define arch_read_lock(lock) \
  93 do {    unsigned long flags; \
  94         local_irq_save(flags); \
  95         __arch_read_lock(lock); \
  96         local_irq_restore(flags); \
  97 } while(0)
  98
  99 static inline void __arch_read_unlock(arch_rwlock_t *rw)
 100 {
 101         register arch_rwlock_t *lp asm("g1");
 102         lp = rw;
 103         __asm__ __volatile__(
 104         "mov    %%o7, %%g4\n\t"
 105         "call   ___rw_read_exit\n\t"
 106         " ldstub        [%%g1 + 3], %%g2\n"
 107         : /* no outputs */
 108         : "r" (lp)
 109         : "g2", "g4", "memory", "cc");
 110 }
 111
 112 #define arch_read_unlock(lock) \
 113 do {    unsigned long flags; \
 114         local_irq_save(flags); \
 115         __arch_read_unlock(lock); \
 116         local_irq_restore(flags); \
 117 } while(0)
 118
 119 static inline void arch_write_lock(arch_rwlock_t *rw)
 120 {
 121         register arch_rwlock_t *lp asm("g1");
 122         lp = rw;
 123         __asm__ __volatile__(
 124         "mov    %%o7, %%g4\n\t"
 125         "call   ___rw_write_enter\n\t"
 126         " ldstub        [%%g1 + 3], %%g2\n"
 127         : /* no outputs */
 128         : "r" (lp)
 129         : "g2", "g4", "memory", "cc");
 130         *(volatile __u32 *)&lp->lock = ~0U;
 131 }
 132
 133 static inline int arch_write_trylock(arch_rwlock_t *rw)
 134 {
 135         unsigned int val;
 136
 137         __asm__ __volatile__("ldstub [%1 + 3], %0"
 138                              : "=r" (val)
 139                              : "r" (&rw->lock)
 140                              : "memory");
 141
 142         if (val == 0) {
 143                 val = rw->lock & ~0xff;
 144                 if (val)
 145                         ((volatile u8*)&rw->lock)[3] = 0;
 146                 else
 147                         *(volatile u32*)&rw->lock = ~0U;
 148         }
 149
 150         return (val == 0);
 151 }
 152
 153 static inline int __arch_read_trylock(arch_rwlock_t *rw)
 154 {
 155         register arch_rwlock_t *lp asm("g1");
 156         register int res asm("o0");
 157         lp = rw;
 158         __asm__ __volatile__(
 159         "mov    %%o7, %%g4\n\t"
 160         "call   ___rw_read_try\n\t"
 161         " ldstub        [%%g1 + 3], %%g2\n"
 162         : "=r" (res)
 163         : "r" (lp)
 164         : "g2", "g4", "memory", "cc");
 165         return res;
 166 }
 167
 168 #define arch_read_trylock(lock) \
 169 ({      unsigned long flags; \
 170         int res; \
 171         local_irq_save(flags); \
 172         res = __arch_read_trylock(lock); \
 173         local_irq_restore(flags); \
 174         res; \
 175 })
 176
 177 #define arch_write_unlock(rw)   do { (rw)->lock = 0; } while(0)
 178
 179 #define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
 180 #define arch_read_lock_flags(rw, flags)   arch_read_lock(rw)
 181 #define arch_write_lock_flags(rw, flags)  arch_write_lock(rw)
 182
 183 #define arch_spin_relax(lock)   cpu_relax()
 184 #define arch_read_relax(lock)   cpu_relax()
 185 #define arch_write_relax(lock)  cpu_relax()
 186
 187 #define arch_read_can_lock(rw) (!((rw)->lock & 0xff))
 188 #define arch_write_can_lock(rw) (!(rw)->lock)
 189
 190 #endif /* !(__ASSEMBLY__) */
 191
 192 #endif /* __SPARC_SPINLOCK_H */