include/linux/rwsem.h

   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  * Trylock by Brian Watson (Brian.J.Watson@compaq.com).
   7  */
   8
   9 #ifndef _LINUX_RWSEM_H
  10 #define _LINUX_RWSEM_H
  11
  12 #include <linux/linkage.h>
  13
  14 #define RWSEM_DEBUG 0
  15
  16 #ifdef __KERNEL__
  17
  18 #include <linux/config.h>
  19 #include <linux/types.h>
  20 #include <linux/kernel.h>
  21 #include <asm/system.h>
  22 #include <asm/atomic.h>
  23
  24 struct rw_semaphore;
  25
  26 #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
  27 #include <linux/rwsem-spinlock.h> /* use a generic implementation */
  28 #else
  29 #include <asm/rwsem.h> /* use an arch-specific implementation */
  30 #endif
  31
  32 #ifndef rwsemtrace
  33 #if RWSEM_DEBUG
  34 extern void FASTCALL(rwsemtrace(struct rw_semaphore *sem, const char *str));
  35 #else
  36 #define rwsemtrace(SEM,FMT)
  37 #endif
  38 #endif
  39
  40 /*
  41  * lock for reading
  42  */
  43 static inline void down_read(struct rw_semaphore *sem)
  44 {
  45         rwsemtrace(sem,"Entering down_read");
  46         __down_read(sem);
  47         rwsemtrace(sem,"Leaving down_read");
  48 }
  49
  50 /*
  51  * trylock for reading -- returns 1 if successful, 0 if contention
  52  */
  53 static inline int down_read_trylock(struct rw_semaphore *sem)
  54 {
  55         int ret;
  56         rwsemtrace(sem,"Entering down_read_trylock");
  57         ret = __down_read_trylock(sem);
  58         rwsemtrace(sem,"Leaving down_read_trylock");
  59         return ret;
  60 }
  61
  62 /*
  63  * lock for writing
  64  */
  65 static inline void down_write(struct rw_semaphore *sem)
  66 {
  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 #endif /* __KERNEL__ */
 106 #endif /* _LINUX_RWSEM_H */