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  1. /*
  2.  * Copyright (C) 2001-2004 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. #ifndef __RWLOCK_H__
  30. #define __RWLOCK_H__
  31.  
  32. #include <arch/types.h>
  33. #include <typedefs.h>
  34. #include <synch/mutex.h>
  35. #include <synch/synch.h>
  36. #include <synch/spinlock.h>
  37.  
  38. enum rwlock_type {
  39.     RWLOCK_NONE,
  40.     RWLOCK_READER,
  41.     RWLOCK_WRITER
  42. };
  43.  
  44. struct rwlock {
  45.     SPINLOCK_DECLARE(lock);
  46.     mutex_t exclusive;  /**< Mutex for writers, readers can bypass it if readers_in is positive. */
  47.     count_t readers_in; /**< Number of readers in critical section. */
  48. };
  49.  
  50. #define rwlock_write_lock(rwl) \
  51.     _rwlock_write_lock_timeout((rwl),SYNCH_NO_TIMEOUT,SYNCH_BLOCKING)
  52. #define rwlock_read_lock(rwl) \
  53.     _rwlock_read_lock_timeout((rwl),SYNCH_NO_TIMEOUT,SYNCH_BLOCKING)
  54. #define rwlock_write_trylock(rwl) \
  55.     _rwlock_write_lock_timeout((rwl),SYNCH_NO_TIMEOUT,SYNCH_NON_BLOCKING)
  56. #define rwlock_read_trylock(rwl) \
  57.     _rwlock_read_lock_timeout((rwl),SYNCH_NO_TIMEOUT,SYNCH_NON_BLOCKING)
  58. #define rwlock_write_lock_timeout(rwl,usec) \
  59.     _rwlock_write_lock_timeout((rwl),(usec),SYNCH_NON_BLOCKING)
  60. #define rwlock_read_lock_timeout(rwl,usec) \
  61.     _rwlock_read_lock_timeout((rwl),(usec),SYNCH_NON_BLOCKING)
  62.  
  63. extern void rwlock_initialize(rwlock_t *rwl);
  64. extern void rwlock_read_unlock(rwlock_t *rwl);
  65. extern void rwlock_write_unlock(rwlock_t *rwl);
  66. extern int _rwlock_read_lock_timeout(rwlock_t *rwl, __u32 usec, int trylock);
  67. extern int _rwlock_write_lock_timeout(rwlock_t *rwl, __u32 usec, int trylock);
  68.  
  69. #endif
  70.