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 */ 132