1  #ifndef __LINUX_SPINLOCK_UP_H
2  #define __LINUX_SPINLOCK_UP_H
3  
4  #ifndef __LINUX_INSIDE_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  
arch_spin_lock(arch_spinlock_t * lock)29  static inline void arch_spin_lock(arch_spinlock_t *lock)
30  {
31  	lock->slock = 0;
32  	barrier();
33  }
34  
arch_spin_trylock(arch_spinlock_t * lock)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  
arch_spin_unlock(arch_spinlock_t * lock)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_unlock(lock)	do { barrier(); (void)(lock); } while (0)
66  # define arch_spin_trylock(lock)	({ barrier(); (void)(lock); 1; })
67  #endif /* DEBUG_SPINLOCK */
68  
69  #define arch_spin_is_contended(lock)	(((void)(lock), 0))
70  
71  #endif /* __LINUX_SPINLOCK_UP_H */
72