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_unlock_wait(arch_spinlock_t *lock)
  30 {
  31         smp_cond_load_acquire(&lock->slock, VAL);
  32 }
  33
  34 static inline void arch_spin_lock(arch_spinlock_t *lock)
  35 {
  36         lock->slock = 0;
  37         barrier();
  38 }
  39
  40 static inline void
  41 arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
  42 {
  43         local_irq_save(flags);
  44         lock->slock = 0;
  45         barrier();
  46 }
  47
  48 static inline int arch_spin_trylock(arch_spinlock_t *lock)
  49 {
  50         char oldval = lock->slock;
  51
  52         lock->slock = 0;
  53         barrier();
  54
  55         return oldval > 0;
  56 }
  57
  58 static inline void arch_spin_unlock(arch_spinlock_t *lock)
  59 {
  60         barrier();
  61         lock->slock = 1;
  62 }
  63
  64 /*
  65  * Read-write spinlocks. No debug version.
  66  */
  67 #define arch_read_lock(lock)            do { barrier(); (void)(lock); } while (0)
  68 #define arch_write_lock(lock)           do { barrier(); (void)(lock); } while (0)
  69 #define arch_read_trylock(lock) ({ barrier(); (void)(lock); 1; })
  70 #define arch_write_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  71 #define arch_read_unlock(lock)          do { barrier(); (void)(lock); } while (0)
  72 #define arch_write_unlock(lock) do { barrier(); (void)(lock); } while (0)
  73
  74 #else /* DEBUG_SPINLOCK */
  75 #define arch_spin_is_locked(lock)       ((void)(lock), 0)
  76 #define arch_spin_unlock_wait(lock)     do { barrier(); (void)(lock); } while (0)
  77 /* for sched/core.c and kernel_lock.c: */
  78 # define arch_spin_lock(lock)           do { barrier(); (void)(lock); } while (0)
  79 # define arch_spin_lock_flags(lock, flags)      do { barrier(); (void)(lock); } while (0)
  80 # define arch_spin_unlock(lock) do { barrier(); (void)(lock); } while (0)
  81 # define arch_spin_trylock(lock)        ({ barrier(); (void)(lock); 1; })
  82 #endif /* DEBUG_SPINLOCK */
  83
  84 #define arch_spin_is_contended(lock)    (((void)(lock), 0))
  85
  86 #define arch_read_can_lock(lock)        (((void)(lock), 1))
  87 #define arch_write_can_lock(lock)       (((void)(lock), 1))
  88
  89 #endif /* __LINUX_SPINLOCK_UP_H */