linux/include/linux/spinlock_up.h
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   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
  10/*
  11 * include/linux/spinlock_up.h - UP-debug version of spinlocks.
  12 *
  13 * portions Copyright 2005, Red Hat, Inc., Ingo Molnar
  14 * Released under the General Public License (GPL).
  15 *
  16 * In the debug case, 1 means unlocked, 0 means locked. (the values
  17 * are inverted, to catch initialization bugs)
  18 *
  19 * No atomicity anywhere, we are on UP. However, we still need
  20 * the compiler barriers, because we do not want the compiler to
  21 * move potentially faulting instructions (notably user accesses)
  22 * into the locked sequence, resulting in non-atomic execution.
  23 */
  24
  25#ifdef CONFIG_DEBUG_SPINLOCK
  26#define arch_spin_is_locked(x)          ((x)->slock == 0)
  27
  28static inline void arch_spin_lock(arch_spinlock_t *lock)
  29{
  30        lock->slock = 0;
  31        barrier();
  32}
  33
  34static inline void
  35arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
  36{
  37        local_irq_save(flags);
  38        lock->slock = 0;
  39        barrier();
  40}
  41
  42static inline int arch_spin_trylock(arch_spinlock_t *lock)
  43{
  44        char oldval = lock->slock;
  45
  46        lock->slock = 0;
  47        barrier();
  48
  49        return oldval > 0;
  50}
  51
  52static inline void arch_spin_unlock(arch_spinlock_t *lock)
  53{
  54        barrier();
  55        lock->slock = 1;
  56}
  57
  58/*
  59 * Read-write spinlocks. No debug version.
  60 */
  61#define arch_read_lock(lock)            do { barrier(); (void)(lock); } while (0)
  62#define arch_write_lock(lock)           do { barrier(); (void)(lock); } while (0)
  63#define arch_read_trylock(lock) ({ barrier(); (void)(lock); 1; })
  64#define arch_write_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  65#define arch_read_unlock(lock)          do { barrier(); (void)(lock); } while (0)
  66#define arch_write_unlock(lock) do { barrier(); (void)(lock); } while (0)
  67
  68#else /* DEBUG_SPINLOCK */
  69#define arch_spin_is_locked(lock)       ((void)(lock), 0)
  70/* for sched.c and kernel_lock.c: */
  71# define arch_spin_lock(lock)           do { barrier(); (void)(lock); } while (0)
  72# define arch_spin_lock_flags(lock, flags)      do { barrier(); (void)(lock); } while (0)
  73# define arch_spin_unlock(lock) do { barrier(); (void)(lock); } while (0)
  74# define arch_spin_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  75#endif /* DEBUG_SPINLOCK */
  76
  77#define arch_spin_is_contended(lock)    (((void)(lock), 0))
  78
  79#define arch_read_can_lock(lock)        (((void)(lock), 1))
  80#define arch_write_can_lock(lock)       (((void)(lock), 1))
  81
  82#define arch_spin_unlock_wait(lock) \
  83                do { cpu_relax(); } while (arch_spin_is_locked(lock))
  84
  85#endif /* __LINUX_SPINLOCK_UP_H */
  86
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