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 #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
  29 static inline void arch_spin_lock(arch_spinlock_t *lock)
  30 {
  31         lock->slock = 0;
  32         barrier();
  33 }
  34
  35 static 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
  45 static 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 */