LXR linux-bk/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
  22struct 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
  32extern 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 */
  41static 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 */
  52static 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 */
  64static 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 */
  75static 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 */
  87static 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 */
  97static 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 */
 107static 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