include/linux/spinlock_up.h

   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
  28 static inline void arch_spin_lock(arch_spinlock_t *lock)
  29 {
  30         lock->slock = 0;
  31         barrier();
  32 }
  33
  34 static inline void
  35 arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
  36 {
  37         local_irq_save(flags);
  38         lock->slock = 0;
  39         barrier();
  40 }
  41
  42 static 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
  52 static 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/core.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 */