LXR linux/include/linux/rwsem-spinlock.h

   1/* rwsem-spinlock.h: fallback C implementation
   2 *
   3 * Copyright (c) 2001   David Howells (dhowells@redhat.com).
   4 * - Derived partially from ideas by Andrea Arcangeli <andrea@suse.de>
   5 * - Derived also from comments by Linus
   6 */
   7
   8#ifndef _LINUX_RWSEM_SPINLOCK_H
   9#define _LINUX_RWSEM_SPINLOCK_H
  10
  11#ifndef _LINUX_RWSEM_H
  12#error "please don't include linux/rwsem-spinlock.h directly, use linux/rwsem.h instead"
  13#endif
  14
  15#include <linux/spinlock.h>
  16#include <linux/list.h>
  17
  18#ifdef __KERNEL__
  19
  20#include <linux/types.h>
  21
  22struct rwsem_waiter;
  23
  24/*
  25 * the rw-semaphore definition
  26 * - if activity is 0 then there are no active readers or writers
  27 * - if activity is +ve then that is the number of active readers
  28 * - if activity is -1 then there is one active writer
  29 * - if wait_list is not empty, then there are processes waiting for the semaphore
  30 */
  31struct rw_semaphore {
  32        __s32                   activity;
  33        spinlock_t              wait_lock;
  34        struct list_head        wait_list;
  35#ifdef CONFIG_DEBUG_LOCK_ALLOC
  36        struct lockdep_map dep_map;
  37#endif
  38};
  39
  40#ifdef CONFIG_DEBUG_LOCK_ALLOC
  41# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname }
  42#else
  43# define __RWSEM_DEP_MAP_INIT(lockname)
  44#endif
  45
  46#define __RWSEM_INITIALIZER(name) \
  47{ 0, __SPIN_LOCK_UNLOCKED(name.wait_lock), LIST_HEAD_INIT((name).wait_list) \
  48  __RWSEM_DEP_MAP_INIT(name) }
  49
  50#define DECLARE_RWSEM(name) \
  51        struct rw_semaphore name = __RWSEM_INITIALIZER(name)
  52
  53extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
  54                         struct lock_class_key *key);
  55
  56#define init_rwsem(sem)                                         \
  57do {                                                            \
  58        static struct lock_class_key __key;                     \
  59                                                                \
  60        __init_rwsem((sem), #sem, &__key);                      \
  61} while (0)
  62
  63extern void __down_read(struct rw_semaphore *sem);
  64extern int __down_read_trylock(struct rw_semaphore *sem);
  65extern void __down_write(struct rw_semaphore *sem);
  66extern void __down_write_nested(struct rw_semaphore *sem, int subclass);
  67extern int __down_write_trylock(struct rw_semaphore *sem);
  68extern void __up_read(struct rw_semaphore *sem);
  69extern void __up_write(struct rw_semaphore *sem);
  70extern void __downgrade_write(struct rw_semaphore *sem);
  71
  72static inline int rwsem_is_locked(struct rw_semaphore *sem)
  73{
  74        return (sem->activity != 0);
  75}
  76
  77#endif /* __KERNEL__ */
  78#endif /* _LINUX_RWSEM_SPINLOCK_H */
  79