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 #include <asm/processor.h>
   8
   9 /*
  10  * Your basic SMP spinlocks, allowing only a single CPU anywhere
  11  *
  12  * Simple spin lock operations.  There are two variants, one clears IRQ's
  13  * on the local processor, one does not.
  14  *
  15  * We make no fairness assumptions. They have a cost.
  16  *
  17  * (the type definitions are in asm/spinlock_types.h)
  18  */
  19
  20 static inline int __raw_spin_is_locked(raw_spinlock_t *lock)
  21 {
  22         return *(volatile signed int *)(&(lock)->slock) <= 0;
  23 }
  24
  25 static inline void __raw_spin_lock(raw_spinlock_t *lock)
  26 {
  27         asm volatile(
  28                 "\n1:\t"
  29                 LOCK_PREFIX " ; decl %0\n\t"
  30                 "jns 2f\n"
  31                 "3:\n"
  32                 "rep;nop\n\t"
  33                 "cmpl $0,%0\n\t"
  34                 "jle 3b\n\t"
  35                 "jmp 1b\n"
  36                 "2:\t" : "=m" (lock->slock) : : "memory");
  37 }
  38
  39 /*
  40  * Same as __raw_spin_lock, but reenable interrupts during spinning.
  41  */
  42 #ifndef CONFIG_PROVE_LOCKING
  43 static inline void __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
  44 {
  45         asm volatile(
  46                 "\n1:\t"
  47                 LOCK_PREFIX " ; decl %0\n\t"
  48                 "jns 5f\n"
  49                 "testl $0x200, %1\n\t"  /* interrupts were disabled? */
  50                 "jz 4f\n\t"
  51                 "sti\n"
  52                 "3:\t"
  53                 "rep;nop\n\t"
  54                 "cmpl $0, %0\n\t"
  55                 "jle 3b\n\t"
  56                 "cli\n\t"
  57                 "jmp 1b\n"
  58                 "4:\t"
  59                 "rep;nop\n\t"
  60                 "cmpl $0, %0\n\t"
  61                 "jg 1b\n\t"
  62                 "jmp 4b\n"
  63                 "5:\n\t"
  64                 : "+m" (lock->slock) : "r" ((unsigned)flags) : "memory");
  65 }
  66 #endif
  67
  68 static inline int __raw_spin_trylock(raw_spinlock_t *lock)
  69 {
  70         int oldval;
  71
  72         asm volatile(
  73                 "xchgl %0,%1"
  74                 :"=q" (oldval), "=m" (lock->slock)
  75                 :"0" (0) : "memory");
  76
  77         return oldval > 0;
  78 }
  79
  80 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
  81 {
  82         asm volatile("movl $1,%0" :"=m" (lock->slock) :: "memory");
  83 }
  84
  85 static inline void __raw_spin_unlock_wait(raw_spinlock_t *lock)
  86 {
  87         while (__raw_spin_is_locked(lock))
  88                 cpu_relax();
  89 }
  90
  91 /*
  92  * Read-write spinlocks, allowing multiple readers
  93  * but only one writer.
  94  *
  95  * NOTE! it is quite common to have readers in interrupts
  96  * but no interrupt writers. For those circumstances we
  97  * can "mix" irq-safe locks - any writer needs to get a
  98  * irq-safe write-lock, but readers can get non-irqsafe
  99  * read-locks.
 100  *
 101  * On x86, we implement read-write locks as a 32-bit counter
 102  * with the high bit (sign) being the "contended" bit.
 103  */
 104
 105 static inline int __raw_read_can_lock(raw_rwlock_t *lock)
 106 {
 107         return (int)(lock)->lock > 0;
 108 }
 109
 110 static inline int __raw_write_can_lock(raw_rwlock_t *lock)
 111 {
 112         return (lock)->lock == RW_LOCK_BIAS;
 113 }
 114
 115 static inline void __raw_read_lock(raw_rwlock_t *rw)
 116 {
 117         asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t"
 118                      "jns 1f\n"
 119                      "call __read_lock_failed\n"
 120                      "1:\n"
 121                      ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory");
 122 }
 123
 124 static inline void __raw_write_lock(raw_rwlock_t *rw)
 125 {
 126         asm volatile(LOCK_PREFIX "subl %1,(%0)\n\t"
 127                      "jz 1f\n"
 128                      "\tcall __write_lock_failed\n\t"
 129                      "1:\n"
 130                      ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory");
 131 }
 132
 133 static inline int __raw_read_trylock(raw_rwlock_t *lock)
 134 {
 135         atomic_t *count = (atomic_t *)lock;
 136         atomic_dec(count);
 137         if (atomic_read(count) >= 0)
 138                 return 1;
 139         atomic_inc(count);
 140         return 0;
 141 }
 142
 143 static inline int __raw_write_trylock(raw_rwlock_t *lock)
 144 {
 145         atomic_t *count = (atomic_t *)lock;
 146         if (atomic_sub_and_test(RW_LOCK_BIAS, count))
 147                 return 1;
 148         atomic_add(RW_LOCK_BIAS, count);
 149         return 0;
 150 }
 151
 152 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 153 {
 154         asm volatile(LOCK_PREFIX " ; incl %0" :"=m" (rw->lock) : : "memory");
 155 }
 156
 157 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 158 {
 159         asm volatile(LOCK_PREFIX " ; addl $" RW_LOCK_BIAS_STR ",%0"
 160                                 : "=m" (rw->lock) : : "memory");
 161 }
 162
 163 #define _raw_spin_relax(lock)   cpu_relax()
 164 #define _raw_read_relax(lock)   cpu_relax()
 165 #define _raw_write_relax(lock)  cpu_relax()
 166
 167 #endif /* __ASM_SPINLOCK_H */