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 void
  36 arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
  37 {
  38         local_irq_save(flags);
  39         lock->slock = 0;
  40         barrier();
  41 }
  42
  43 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  44 {
  45         char oldval = lock->slock;
  46
  47         lock->slock = 0;
  48         barrier();
  49
  50         return oldval > 0;
  51 }
  52
  53 static inline void arch_spin_unlock(arch_spinlock_t *lock)
  54 {
  55         barrier();
  56         lock->slock = 1;
  57 }
  58
  59 /*
  60  * Read-write spinlocks. No debug version.
  61  */
  62 #define arch_read_lock(lock)            do { barrier(); (void)(lock); } while (0)
  63 #define arch_write_lock(lock)           do { barrier(); (void)(lock); } while (0)
  64 #define arch_read_trylock(lock) ({ barrier(); (void)(lock); 1; })
  65 #define arch_write_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  66 #define arch_read_unlock(lock)          do { barrier(); (void)(lock); } while (0)
  67 #define arch_write_unlock(lock) do { barrier(); (void)(lock); } while (0)
  68
  69 #else /* DEBUG_SPINLOCK */
  70 #define arch_spin_is_locked(lock)       ((void)(lock), 0)
  71 /* for sched/core.c and kernel_lock.c: */
  72 # define arch_spin_lock(lock)           do { barrier(); (void)(lock); } while (0)
  73 # define arch_spin_lock_flags(lock, flags)      do { barrier(); (void)(lock); } while (0)
  74 # define arch_spin_unlock(lock) do { barrier(); (void)(lock); } while (0)
  75 # define arch_spin_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  76 #endif /* DEBUG_SPINLOCK */
  77
  78 #define arch_spin_is_contended(lock)    (((void)(lock), 0))
  79
  80 #define arch_read_can_lock(lock)        (((void)(lock), 1))
  81 #define arch_write_can_lock(lock)       (((void)(lock), 1))
  82
  83 #endif /* __LINUX_SPINLOCK_UP_H */