include/sys/condvar_impl.h

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #ifndef _SYS_CONDVAR_IMPL_H
  28 #define _SYS_CONDVAR_IMPL_H
  29
  30 /*
  31  * Implementation-private definitions for condition variables
  32  */
  33
  34 #ifndef _ASM
  35 #include <sys/types.h>
  36 #include <sys/thread.h>
  37 #endif  /* _ASM */
  38
  39 #ifdef  __cplusplus
  40 extern "C" {
  41 #endif
  42
  43 #ifndef _ASM
  44
  45 /*
  46  * Condtion variables.
  47  */
  48
  49 typedef struct _condvar_impl {
  50         ushort_t        cv_waiters;
  51 } condvar_impl_t;
  52
  53 #define CV_HAS_WAITERS(cvp)     (((condvar_impl_t *)(cvp))->cv_waiters != 0)
  54
  55 #endif  /* _ASM */
  56
  57
  58 /*
  59  * The cvwaitlock_t structure and associated macros provide an implementation
  60  * of a locking mechanism that allows recursion on the reader lock without
  61  * danger of a pending write lock elsewhere being able to cause a deadlock.
  62  * The provision for supporting recursion is necessary for use with the
  63  * netinfo (neti) kernel module when processing network data.
  64  *
  65  * Support for recursion (giving precedence to readers and allowing them
  66  * to enter even when a write is blocked) can result in write starvation.
  67  * There is no priority inheritence for this locking interface.
  68  */
  69 typedef struct  cvwaitlock_s    {
  70         kmutex_t        cvw_lock;
  71         kcondvar_t      cvw_waiter;
  72         int             cvw_refcnt;
  73 } cvwaitlock_t;
  74
  75
  76 #define CVW_INIT(_c)            {                               \
  77         mutex_init(&(_c)->cvw_lock, NULL, MUTEX_DRIVER, NULL);  \
  78         cv_init(&(_c)->cvw_waiter, NULL, CV_DRIVER, NULL);      \
  79         (_c)->cvw_refcnt = 0;                                   \
  80 }
  81
  82 #define CVW_ENTER_READ(_c)      {                               \
  83         mutex_enter(&(_c)->cvw_lock);                           \
  84         while ((_c)->cvw_refcnt < 0)                            \
  85                 cv_wait(&((_c)->cvw_waiter), &(_c)->cvw_lock);  \
  86         (_c)->cvw_refcnt++;                                     \
  87         mutex_exit(&(_c)->cvw_lock);                            \
  88 }
  89
  90 #define CVW_ENTER_WRITE(_c)     {                               \
  91         mutex_enter(&(_c)->cvw_lock);                           \
  92         while ((_c)->cvw_refcnt != 0)                           \
  93                 cv_wait(&((_c)->cvw_waiter), &(_c)->cvw_lock);  \
  94         (_c)->cvw_refcnt = -1;                                  \
  95         mutex_exit(&(_c)->cvw_lock);                            \
  96 }
  97
  98 #define CVW_EXIT_READ(_c)       {                       \
  99         mutex_enter(&(_c)->cvw_lock);                   \
 100         ASSERT((_c)->cvw_refcnt > 0);                   \
 101         if ((--((_c)->cvw_refcnt)) == 0)                \
 102                 cv_broadcast(&(_c)->cvw_waiter);        \
 103         mutex_exit(&(_c)->cvw_lock);                    \
 104 }
 105
 106 #define CVW_EXIT_WRITE(_c)      {                       \
 107         mutex_enter(&(_c)->cvw_lock);                   \
 108         ASSERT((_c)->cvw_refcnt == -1);                 \
 109         (_c)->cvw_refcnt = 0;                           \
 110         cv_broadcast(&(_c)->cvw_waiter);                \
 111         mutex_exit(&(_c)->cvw_lock);                    \
 112 }
 113
 114 #define CVW_WRITE_TO_READ(_c)   {                       \
 115         mutex_enter(&(_c)->cvw_lock);                   \
 116         ASSERT((_c)->cvw_refcnt == -1);                 \
 117         (_c)->cvw_refcnt = 1;                           \
 118         cv_broadcast(&(_c)->cvw_waiter);                \
 119         mutex_exit(&(_c)->cvw_lock);                    \
 120 }
 121
 122 #define CVW_DESTROY(_c) {                               \
 123         mutex_destroy(&(_c)->cvw_lock);                 \
 124         cv_destroy(&(_c)->cvw_waiter);                  \
 125 }
 126
 127 #ifdef  __cplusplus
 128 }
 129 #endif
 130
 131 #endif  /* _SYS_CONDVAR_IMPL_H */