LXR linux/include/linux/spinlock

   1#ifndef __LINUX_SPINLOCK_UP_H
   2#define __LINUX_SPINLOCK_UP_H
   3
   4#ifndef __LINUX_SPINLOCK_H
   5# error "please don't include this file directly"
   6#endif
   7
   8#include <asm/processor.h>      /* for cpu_relax() */
   9#include <asm/barrier.h>
  10
  11/*
  12 * include/linux/spinlock_up.h - UP-debug version of spinlocks.
  13 *
  14 * portions Copyright 2005, Red Hat, Inc., Ingo Molnar
  15 * Released under the General Public License (GPL).
  16 *
  17 * In the debug case, 1 means unlocked, 0 means locked. (the values
  18 * are inverted, to catch initialization bugs)
  19 *
  20 * No atomicity anywhere, we are on UP. However, we still need
  21 * the compiler barriers, because we do not want the compiler to
  22 * move potentially faulting instructions (notably user accesses)
  23 * into the locked sequence, resulting in non-atomic execution.
  24 */
  25
  26#ifdef CONFIG_DEBUG_SPINLOCK
  27#define arch_spin_is_locked(x)          ((x)->slock == 0)
  28
  29static inline void arch_spin_lock(arch_spinlock_t *lock)
  30{
  31        lock->slock = 0;
  32        barrier();
  33}
  34
  35static inline int arch_spin_trylock(arch_spinlock_t *lock)
  36{
  37        char oldval = lock->slock;
  38
  39        lock->slock = 0;
  40        barrier();
  41
  42        return oldval > 0;
  43}
  44
  45static inline void arch_spin_unlock(arch_spinlock_t *lock)
  46{
  47        barrier();
  48        lock->slock = 1;
  49}
  50
  51/*
  52 * Read-write spinlocks. No debug version.
  53 */
  54#define arch_read_lock(lock)            do { barrier(); (void)(lock); } while (0)
  55#define arch_write_lock(lock)           do { barrier(); (void)(lock); } while (0)
  56#define arch_read_trylock(lock) ({ barrier(); (void)(lock); 1; })
  57#define arch_write_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  58#define arch_read_unlock(lock)          do { barrier(); (void)(lock); } while (0)
  59#define arch_write_unlock(lock) do { barrier(); (void)(lock); } while (0)
  60
  61#else /* DEBUG_SPINLOCK */
  62#define arch_spin_is_locked(lock)       ((void)(lock), 0)
  63/* for sched/core.c and kernel_lock.c: */
  64# define arch_spin_lock(lock)           do { barrier(); (void)(lock); } while (0)
  65# define arch_spin_lock_flags(lock, flags)      do { barrier(); (void)(lock); } while (0)
  66# define arch_spin_unlock(lock) do { barrier(); (void)(lock); } while (0)
  67# define arch_spin_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  68#endif /* DEBUG_SPINLOCK */
  69
  70#define arch_spin_is_contended(lock)    (((void)(lock), 0))
  71
  72#endif /* __LINUX_SPINLOCK_UP_H */
  73