include/asm-x86_64/spinlock.h

   1 #ifndef __ASM_SPINLOCK_H
   2 #define __ASM_SPINLOCK_H
   3
   4 #include <asm/atomic.h>
   5 #include <asm/rwlock.h>
   6 #include <asm/page.h>
   7
   8 /*
   9  * Your basic SMP spinlocks, allowing only a single CPU anywhere
  10  *
  11  * Simple spin lock operations.  There are two variants, one clears IRQ's
  12  * on the local processor, one does not.
  13  *
  14  * We make no fairness assumptions. They have a cost.
  15  *
  16  * (the type definitions are in asm/spinlock_types.h)
  17  */
  18
  19 #define __raw_spin_is_locked(x) \
  20                 (*(volatile signed int *)(&(x)->slock) <= 0)
  21
  22 #define __raw_spin_lock_string \
  23         "\n1:\t" \
  24         "lock ; decl %0\n\t" \
  25         "js 2f\n" \
  26         LOCK_SECTION_START("") \
  27         "2:\t" \
  28         "rep;nop\n\t" \
  29         "cmpl $0,%0\n\t" \
  30         "jle 2b\n\t" \
  31         "jmp 1b\n" \
  32         LOCK_SECTION_END
  33
  34 #define __raw_spin_unlock_string \
  35         "movl $1,%0" \
  36                 :"=m" (lock->slock) : : "memory"
  37
  38 static inline void __raw_spin_lock(raw_spinlock_t *lock)
  39 {
  40         __asm__ __volatile__(
  41                 __raw_spin_lock_string
  42                 :"=m" (lock->slock) : : "memory");
  43 }
  44
  45 #define __raw_spin_lock_flags(lock, flags) __raw_spin_lock(lock)
  46
  47 static inline int __raw_spin_trylock(raw_spinlock_t *lock)
  48 {
  49         int oldval;
  50
  51         __asm__ __volatile__(
  52                 "xchgl %0,%1"
  53                 :"=q" (oldval), "=m" (lock->slock)
  54                 :"0" (0) : "memory");
  55
  56         return oldval > 0;
  57 }
  58
  59 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
  60 {
  61         __asm__ __volatile__(
  62                 __raw_spin_unlock_string
  63         );
  64 }
  65
  66 #define __raw_spin_unlock_wait(lock) \
  67         do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
  68
  69 /*
  70  * Read-write spinlocks, allowing multiple readers
  71  * but only one writer.
  72  *
  73  * NOTE! it is quite common to have readers in interrupts
  74  * but no interrupt writers. For those circumstances we
  75  * can "mix" irq-safe locks - any writer needs to get a
  76  * irq-safe write-lock, but readers can get non-irqsafe
  77  * read-locks.
  78  *
  79  * On x86, we implement read-write locks as a 32-bit counter
  80  * with the high bit (sign) being the "contended" bit.
  81  *
  82  * The inline assembly is non-obvious. Think about it.
  83  *
  84  * Changed to use the same technique as rw semaphores.  See
  85  * semaphore.h for details.  -ben
  86  *
  87  * the helpers are in arch/i386/kernel/semaphore.c
  88  */
  89
  90 #define __raw_read_can_lock(x)          ((int)(x)->lock > 0)
  91 #define __raw_write_can_lock(x)         ((x)->lock == RW_LOCK_BIAS)
  92
  93 static inline void __raw_read_lock(raw_rwlock_t *rw)
  94 {
  95         __build_read_lock(rw, "__read_lock_failed");
  96 }
  97
  98 static inline void __raw_write_lock(raw_rwlock_t *rw)
  99 {
 100         __build_write_lock(rw, "__write_lock_failed");
 101 }
 102
 103 static inline int __raw_read_trylock(raw_rwlock_t *lock)
 104 {
 105         atomic_t *count = (atomic_t *)lock;
 106         atomic_dec(count);
 107         if (atomic_read(count) >= 0)
 108                 return 1;
 109         atomic_inc(count);
 110         return 0;
 111 }
 112
 113 static inline int __raw_write_trylock(raw_rwlock_t *lock)
 114 {
 115         atomic_t *count = (atomic_t *)lock;
 116         if (atomic_sub_and_test(RW_LOCK_BIAS, count))
 117                 return 1;
 118         atomic_add(RW_LOCK_BIAS, count);
 119         return 0;
 120 }
 121
 122 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 123 {
 124         asm volatile("lock ; incl %0" :"=m" (rw->lock) : : "memory");
 125 }
 126
 127 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 128 {
 129         asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ",%0"
 130                                 : "=m" (rw->lock) : : "memory");
 131 }
 132
 133 #endif /* __ASM_SPINLOCK_H */