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
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_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
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