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 * Copyright 2007 Sun Microsystems, Inc. All rights reserved. 23 * Use is subject to license terms. 24 */ 25 26 #ifndef _SYS_RR_RW_LOCK_H 27 #define _SYS_RR_RW_LOCK_H 28 29 #pragma ident "%Z%%M% %I% %E% SMI" 30 31 #ifdef __cplusplus 32 extern "C" { 33 #endif 34 35 #include <sys/inttypes.h> 36 #include <sys/zfs_context.h> 37 #include <sys/refcount.h> 38 39 /* 40 * A reader-writer lock implementation that allows re-entrant reads, but 41 * still gives writers priority on "new" reads. 42 * 43 * See rrwlock.c for more details about the implementation. 44 * 45 * Fields of the rrwlock_t structure: 46 * - rr_lock: protects modification and reading of rrwlock_t fields 47 * - rr_cv: cv for waking up readers or waiting writers 48 * - rr_writer: thread id of the current writer 49 * - rr_anon_rount: number of active anonymous readers 50 * - rr_linked_rcount: total number of non-anonymous active readers 51 * - rr_writer_wanted: a writer wants the lock 52 */ 53 typedef struct rrwlock { 54 kmutex_t rr_lock; 55 kcondvar_t rr_cv; 56 kthread_t *rr_writer; 57 refcount_t rr_anon_rcount; 58 refcount_t rr_linked_rcount; 59 boolean_t rr_writer_wanted; 60 } rrwlock_t; 61 62 /* 63 * 'tag' is used in reference counting tracking. The 64 * 'tag' must be the same in a rrw_enter() as in its 65 * corresponding rrw_exit(). 66 */ 67 void rrw_init(rrwlock_t *rrl); 68 void rrw_destroy(rrwlock_t *rrl); 69 void rrw_enter(rrwlock_t *rrl, krw_t rw, void *tag); 70 void rrw_exit(rrwlock_t *rrl, void *tag); 71 boolean_t rrw_held(rrwlock_t *rrl, krw_t rw); 72 73 #define RRW_READ_HELD(x) rrw_held(x, RW_READER) 74 #define RRW_WRITE_HELD(x) rrw_held(x, RW_WRITER) 75 76 #ifdef __cplusplus 77 } 78 #endif 79 80 #endif /* _SYS_RR_RW_LOCK_H */ 81