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
   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 */