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Linux/include/linux/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 #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 */
 90 

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