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C/C++ Source or Header  |  2005-10-13  |  2KB  |  116 lines
  1. /* rwsem.h: R/W semaphores, public interface
  2.  *
  3.  * Written by David Howells (dhowells@redhat.com).
  4.  * Derived from asm-i386/semaphore.h
  5.  */
  6.  
  7. #ifndef _LINUX_RWSEM_H
  8. #define _LINUX_RWSEM_H
  9.  
  10. #include <linux/linkage.h>
  11.  
  12. #define RWSEM_DEBUG 0
  13.  
  14. #ifdef __KERNEL__
  15.  
  16. #include <linux/config.h>
  17. #include <linux/types.h>
  18. #include <linux/kernel.h>
  19. #include <asm/system.h>
  20. #include <asm/atomic.h>
  21.  
  22. struct rw_semaphore;
  23.  
  24. #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
  25. #include <linux/rwsem-spinlock.h> /* use a generic implementation */
  26. #else
  27. #include <asm/rwsem.h> /* use an arch-specific implementation */
  28. #endif
  29.  
  30. #ifndef rwsemtrace
  31. #if RWSEM_DEBUG
  32. extern void FASTCALL(rwsemtrace(struct rw_semaphore *sem, const char *str));
  33. #else
  34. #define rwsemtrace(SEM,FMT)
  35. #endif
  36. #endif
  37.  
  38. /*
  39.  * lock for reading
  40.  */
  41. static inline void down_read(struct rw_semaphore *sem)
  42. {
  43.     might_sleep();
  44.     rwsemtrace(sem,"Entering down_read");
  45.     __down_read(sem);
  46.     rwsemtrace(sem,"Leaving down_read");
  47. }
  48.  
  49. /*
  50.  * trylock for reading -- returns 1 if successful, 0 if contention
  51.  */
  52. static inline int down_read_trylock(struct rw_semaphore *sem)
  53. {
  54.     int ret;
  55.     rwsemtrace(sem,"Entering down_read_trylock");
  56.     ret = __down_read_trylock(sem);
  57.     rwsemtrace(sem,"Leaving down_read_trylock");
  58.     return ret;
  59. }
  60.  
  61. /*
  62.  * lock for writing
  63.  */
  64. static inline void down_write(struct rw_semaphore *sem)
  65. {
  66.     might_sleep();
  67.     rwsemtrace(sem,"Entering down_write");
  68.     __down_write(sem);
  69.     rwsemtrace(sem,"Leaving down_write");
  70. }
  71.  
  72. /*
  73.  * trylock for writing -- returns 1 if successful, 0 if contention
  74.  */
  75. static inline int down_write_trylock(struct rw_semaphore *sem)
  76. {
  77.     int ret;
  78.     rwsemtrace(sem,"Entering down_write_trylock");
  79.     ret = __down_write_trylock(sem);
  80.     rwsemtrace(sem,"Leaving down_write_trylock");
  81.     return ret;
  82. }
  83.  
  84. /*
  85.  * release a read lock
  86.  */
  87. static inline void up_read(struct rw_semaphore *sem)
  88. {
  89.     rwsemtrace(sem,"Entering up_read");
  90.     __up_read(sem);
  91.     rwsemtrace(sem,"Leaving up_read");
  92. }
  93.  
  94. /*
  95.  * release a write lock
  96.  */
  97. static inline void up_write(struct rw_semaphore *sem)
  98. {
  99.     rwsemtrace(sem,"Entering up_write");
  100.     __up_write(sem);
  101.     rwsemtrace(sem,"Leaving up_write");
  102. }
  103.  
  104. /*
  105.  * downgrade write lock to read lock
  106.  */
  107. static inline void downgrade_write(struct rw_semaphore *sem)
  108. {
  109.     rwsemtrace(sem,"Entering downgrade_write");
  110.     __downgrade_write(sem);
  111.     rwsemtrace(sem,"Leaving downgrade_write");
  112. }
  113.  
  114. #endif /* __KERNEL__ */
  115. #endif /* _LINUX_RWSEM_H */
  116.