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 
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_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 */
73