include/asm-i386/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 <linux/config.h>
   8 #include <linux/compiler.h>
   9
  10 /*
  11  * Your basic SMP spinlocks, allowing only a single CPU anywhere
  12  *
  13  * Simple spin lock operations.  There are two variants, one clears IRQ's
  14  * on the local processor, one does not.
  15  *
  16  * We make no fairness assumptions. They have a cost.
  17  *
  18  * (the type definitions are in asm/spinlock_types.h)
  19  */
  20
  21 #define __raw_spin_is_locked(x) \
  22                 (*(volatile signed char *)(&(x)->slock) <= 0)
  23
  24 #define __raw_spin_lock_string \
  25         "\n1:\t" \
  26         "lock ; decb %0\n\t" \
  27         "jns 3f\n" \
  28         "2:\t" \
  29         "rep;nop\n\t" \
  30         "cmpb $0,%0\n\t" \
  31         "jle 2b\n\t" \
  32         "jmp 1b\n" \
  33         "3:\n\t"
  34
  35 #define __raw_spin_lock_string_flags \
  36         "\n1:\t" \
  37         "lock ; decb %0\n\t" \
  38         "jns 4f\n\t" \
  39         "2:\t" \
  40         "testl $0x200, %1\n\t" \
  41         "jz 3f\n\t" \
  42         "sti\n\t" \
  43         "3:\t" \
  44         "rep;nop\n\t" \
  45         "cmpb $0, %0\n\t" \
  46         "jle 3b\n\t" \
  47         "cli\n\t" \
  48         "jmp 1b\n" \
  49         "4:\n\t"
  50
  51 static inline void __raw_spin_lock(raw_spinlock_t *lock)
  52 {
  53         __asm__ __volatile__(
  54                 __raw_spin_lock_string
  55                 :"=m" (lock->slock) : : "memory");
  56 }
  57
  58 static inline void __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
  59 {
  60         __asm__ __volatile__(
  61                 __raw_spin_lock_string_flags
  62                 :"=m" (lock->slock) : "r" (flags) : "memory");
  63 }
  64
  65 static inline int __raw_spin_trylock(raw_spinlock_t *lock)
  66 {
  67         char oldval;
  68         __asm__ __volatile__(
  69                 "xchgb %b0,%1"
  70                 :"=q" (oldval), "=m" (lock->slock)
  71                 :"0" (0) : "memory");
  72         return oldval > 0;
  73 }
  74
  75 /*
  76  * __raw_spin_unlock based on writing $1 to the low byte.
  77  * This method works. Despite all the confusion.
  78  * (except on PPro SMP or if we are using OOSTORE, so we use xchgb there)
  79  * (PPro errata 66, 92)
  80  */
  81
  82 #if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE)
  83
  84 #define __raw_spin_unlock_string \
  85         "movb $1,%0" \
  86                 :"=m" (lock->slock) : : "memory"
  87
  88
  89 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
  90 {
  91         __asm__ __volatile__(
  92                 __raw_spin_unlock_string
  93         );
  94 }
  95
  96 #else
  97
  98 #define __raw_spin_unlock_string \
  99         "xchgb %b0, %1" \
 100                 :"=q" (oldval), "=m" (lock->slock) \
 101                 :"0" (oldval) : "memory"
 102
 103 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
 104 {
 105         char oldval = 1;
 106
 107         __asm__ __volatile__(
 108                 __raw_spin_unlock_string
 109         );
 110 }
 111
 112 #endif
 113
 114 #define __raw_spin_unlock_wait(lock) \
 115         do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
 116
 117 /*
 118  * Read-write spinlocks, allowing multiple readers
 119  * but only one writer.
 120  *
 121  * NOTE! it is quite common to have readers in interrupts
 122  * but no interrupt writers. For those circumstances we
 123  * can "mix" irq-safe locks - any writer needs to get a
 124  * irq-safe write-lock, but readers can get non-irqsafe
 125  * read-locks.
 126  *
 127  * On x86, we implement read-write locks as a 32-bit counter
 128  * with the high bit (sign) being the "contended" bit.
 129  *
 130  * The inline assembly is non-obvious. Think about it.
 131  *
 132  * Changed to use the same technique as rw semaphores.  See
 133  * semaphore.h for details.  -ben
 134  *
 135  * the helpers are in arch/i386/kernel/semaphore.c
 136  */
 137
 138 /**
 139  * read_can_lock - would read_trylock() succeed?
 140  * @lock: the rwlock in question.
 141  */
 142 #define __raw_read_can_lock(x)          ((int)(x)->lock > 0)
 143
 144 /**
 145  * write_can_lock - would write_trylock() succeed?
 146  * @lock: the rwlock in question.
 147  */
 148 #define __raw_write_can_lock(x)         ((x)->lock == RW_LOCK_BIAS)
 149
 150 static inline void __raw_read_lock(raw_rwlock_t *rw)
 151 {
 152         __build_read_lock(rw, "__read_lock_failed");
 153 }
 154
 155 static inline void __raw_write_lock(raw_rwlock_t *rw)
 156 {
 157         __build_write_lock(rw, "__write_lock_failed");
 158 }
 159
 160 static inline int __raw_read_trylock(raw_rwlock_t *lock)
 161 {
 162         atomic_t *count = (atomic_t *)lock;
 163         atomic_dec(count);
 164         if (atomic_read(count) >= 0)
 165                 return 1;
 166         atomic_inc(count);
 167         return 0;
 168 }
 169
 170 static inline int __raw_write_trylock(raw_rwlock_t *lock)
 171 {
 172         atomic_t *count = (atomic_t *)lock;
 173         if (atomic_sub_and_test(RW_LOCK_BIAS, count))
 174                 return 1;
 175         atomic_add(RW_LOCK_BIAS, count);
 176         return 0;
 177 }
 178
 179 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 180 {
 181         asm volatile("lock ; incl %0" :"=m" (rw->lock) : : "memory");
 182 }
 183
 184 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 185 {
 186         asm volatile("lock ; addl $" RW_LOCK_BIAS_STR ", %0"
 187                                  : "=m" (rw->lock) : : "memory");
 188 }
 189
 190 #endif /* __ASM_SPINLOCK_H */