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/compiler.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 #define __raw_spin_is_locked(x) \
  21                 (*(volatile signed char *)(&(x)->slock) <= 0)
  22
  23 #define __raw_spin_lock_string \
  24         "\n1:\t" \
  25         "lock ; decb %0\n\t" \
  26         "jns 3f\n" \
  27         "2:\t" \
  28         "rep;nop\n\t" \
  29         "cmpb $0,%0\n\t" \
  30         "jle 2b\n\t" \
  31         "jmp 1b\n" \
  32         "3:\n\t"
  33
  34 #define __raw_spin_lock_string_flags \
  35         "\n1:\t" \
  36         "lock ; decb %0\n\t" \
  37         "jns 5f\n" \
  38         "2:\t" \
  39         "testl $0x200, %1\n\t" \
  40         "jz 4f\n\t" \
  41         "sti\n" \
  42         "3:\t" \
  43         "rep;nop\n\t" \
  44         "cmpb $0, %0\n\t" \
  45         "jle 3b\n\t" \
  46         "cli\n\t" \
  47         "jmp 1b\n" \
  48         "4:\t" \
  49         "rep;nop\n\t" \
  50         "cmpb $0, %0\n\t" \
  51         "jg 1b\n\t" \
  52         "jmp 4b\n" \
  53         "5:\n\t"
  54
  55 #define __raw_spin_lock_string_up \
  56         "\n\tdecb %0"
  57
  58 static inline void __raw_spin_lock(raw_spinlock_t *lock)
  59 {
  60         alternative_smp(
  61                 __raw_spin_lock_string,
  62                 __raw_spin_lock_string_up,
  63                 "=m" (lock->slock) : : "memory");
  64 }
  65
  66 static inline void __raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long flags)
  67 {
  68         alternative_smp(
  69                 __raw_spin_lock_string_flags,
  70                 __raw_spin_lock_string_up,
  71                 "=m" (lock->slock) : "r" (flags) : "memory");
  72 }
  73
  74 static inline int __raw_spin_trylock(raw_spinlock_t *lock)
  75 {
  76         char oldval;
  77         __asm__ __volatile__(
  78                 "xchgb %b0,%1"
  79                 :"=q" (oldval), "=m" (lock->slock)
  80                 :"0" (0) : "memory");
  81         return oldval > 0;
  82 }
  83
  84 /*
  85  * __raw_spin_unlock based on writing $1 to the low byte.
  86  * This method works. Despite all the confusion.
  87  * (except on PPro SMP or if we are using OOSTORE, so we use xchgb there)
  88  * (PPro errata 66, 92)
  89  */
  90
  91 #if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE)
  92
  93 #define __raw_spin_unlock_string \
  94         "movb $1,%0" \
  95                 :"=m" (lock->slock) : : "memory"
  96
  97
  98 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
  99 {
 100         __asm__ __volatile__(
 101                 __raw_spin_unlock_string
 102         );
 103 }
 104
 105 #else
 106
 107 #define __raw_spin_unlock_string \
 108         "xchgb %b0, %1" \
 109                 :"=q" (oldval), "=m" (lock->slock) \
 110                 :"0" (oldval) : "memory"
 111
 112 static inline void __raw_spin_unlock(raw_spinlock_t *lock)
 113 {
 114         char oldval = 1;
 115
 116         __asm__ __volatile__(
 117                 __raw_spin_unlock_string
 118         );
 119 }
 120
 121 #endif
 122
 123 #define __raw_spin_unlock_wait(lock) \
 124         do { while (__raw_spin_is_locked(lock)) cpu_relax(); } while (0)
 125
 126 /*
 127  * Read-write spinlocks, allowing multiple readers
 128  * but only one writer.
 129  *
 130  * NOTE! it is quite common to have readers in interrupts
 131  * but no interrupt writers. For those circumstances we
 132  * can "mix" irq-safe locks - any writer needs to get a
 133  * irq-safe write-lock, but readers can get non-irqsafe
 134  * read-locks.
 135  *
 136  * On x86, we implement read-write locks as a 32-bit counter
 137  * with the high bit (sign) being the "contended" bit.
 138  *
 139  * The inline assembly is non-obvious. Think about it.
 140  *
 141  * Changed to use the same technique as rw semaphores.  See
 142  * semaphore.h for details.  -ben
 143  *
 144  * the helpers are in arch/i386/kernel/semaphore.c
 145  */
 146
 147 /**
 148  * read_can_lock - would read_trylock() succeed?
 149  * @lock: the rwlock in question.
 150  */
 151 #define __raw_read_can_lock(x)          ((int)(x)->lock > 0)
 152
 153 /**
 154  * write_can_lock - would write_trylock() succeed?
 155  * @lock: the rwlock in question.
 156  */
 157 #define __raw_write_can_lock(x)         ((x)->lock == RW_LOCK_BIAS)
 158
 159 static inline void __raw_read_lock(raw_rwlock_t *rw)
 160 {
 161         __build_read_lock(rw, "__read_lock_failed");
 162 }
 163
 164 static inline void __raw_write_lock(raw_rwlock_t *rw)
 165 {
 166         __build_write_lock(rw, "__write_lock_failed");
 167 }
 168
 169 static inline int __raw_read_trylock(raw_rwlock_t *lock)
 170 {
 171         atomic_t *count = (atomic_t *)lock;
 172         atomic_dec(count);
 173         if (atomic_read(count) >= 0)
 174                 return 1;
 175         atomic_inc(count);
 176         return 0;
 177 }
 178
 179 static inline int __raw_write_trylock(raw_rwlock_t *lock)
 180 {
 181         atomic_t *count = (atomic_t *)lock;
 182         if (atomic_sub_and_test(RW_LOCK_BIAS, count))
 183                 return 1;
 184         atomic_add(RW_LOCK_BIAS, count);
 185         return 0;
 186 }
 187
 188 static inline void __raw_read_unlock(raw_rwlock_t *rw)
 189 {
 190         asm volatile(LOCK_PREFIX "incl %0" :"=m" (rw->lock) : : "memory");
 191 }
 192
 193 static inline void __raw_write_unlock(raw_rwlock_t *rw)
 194 {
 195         asm volatile(LOCK_PREFIX "addl $" RW_LOCK_BIAS_STR ", %0"
 196                                  : "=m" (rw->lock) : : "memory");
 197 }
 198
 199 #endif /* __ASM_SPINLOCK_H */