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spinlock_up.h
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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 
10 /*
11  * include/linux/spinlock_up.h - UP-debug version of spinlocks.
12  *
13  * portions Copyright 2005, Red Hat, Inc., Ingo Molnar
14  * Released under the General Public License (GPL).
15  *
16  * In the debug case, 1 means unlocked, 0 means locked. (the values
17  * are inverted, to catch initialization bugs)
18  *
19  * No atomicity anywhere, we are on UP.
20  */
21 
22 #ifdef CONFIG_DEBUG_SPINLOCK
23 #define arch_spin_is_locked(x) ((x)->slock == 0)
24 
25 static inline void arch_spin_lock(arch_spinlock_t *lock)
26 {
27  lock->slock = 0;
28 }
29 
30 static inline void
31 arch_spin_lock_flags(arch_spinlock_t *lock, unsigned long flags)
32 {
33  local_irq_save(flags);
34  lock->slock = 0;
35 }
36 
37 static inline int arch_spin_trylock(arch_spinlock_t *lock)
38 {
39  char oldval = lock->slock;
40 
41  lock->slock = 0;
42 
43  return oldval > 0;
44 }
45 
46 static inline void arch_spin_unlock(arch_spinlock_t *lock)
47 {
48  lock->slock = 1;
49 }
50 
51 /*
52  * Read-write spinlocks. No debug version.
53  */
54 #define arch_read_lock(lock) do { (void)(lock); } while (0)
55 #define arch_write_lock(lock) do { (void)(lock); } while (0)
56 #define arch_read_trylock(lock) ({ (void)(lock); 1; })
57 #define arch_write_trylock(lock) ({ (void)(lock); 1; })
58 #define arch_read_unlock(lock) do { (void)(lock); } while (0)
59 #define arch_write_unlock(lock) do { (void)(lock); } while (0)
60 
61 #else /* DEBUG_SPINLOCK */
62 #define arch_spin_is_locked(lock) ((void)(lock), 0)
63 /* for sched.c and kernel_lock.c: */
64 # define arch_spin_lock(lock) do { (void)(lock); } while (0)
65 # define arch_spin_lock_flags(lock, flags) do { (void)(lock); } while (0)
66 # define arch_spin_unlock(lock) do { (void)(lock); } while (0)
67 # define arch_spin_trylock(lock) ({ (void)(lock); 1; })
68 #endif /* DEBUG_SPINLOCK */
69 
70 #define arch_spin_is_contended(lock) (((void)(lock), 0))
71 
72 #define arch_read_can_lock(lock) (((void)(lock), 1))
73 #define arch_write_can_lock(lock) (((void)(lock), 1))
74 
75 #define arch_spin_unlock_wait(lock) \
76  do { cpu_relax(); } while (arch_spin_is_locked(lock))
77 
78 #endif /* __LINUX_SPINLOCK_UP_H */