1 /* 2 * Copyright (c) 2021 Apple Inc. All rights reserved. 3 * 4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ 5 * 6 * This file contains Original Code and/or Modifications of Original Code 7 * as defined in and that are subject to the Apple Public Source License 8 * Version 2.0 (the 'License'). You may not use this file except in 9 * compliance with the License. The rights granted to you under the License 10 * may not be used to create, or enable the creation or redistribution of, 11 * unlawful or unlicensed copies of an Apple operating system, or to 12 * circumvent, violate, or enable the circumvention or violation of, any 13 * terms of an Apple operating system software license agreement. 14 * 15 * Please obtain a copy of the License at 16 * http://www.opensource.apple.com/apsl/ and read it before using this file. 17 * 18 * The Original Code and all software distributed under the License are 19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, 21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 23 * Please see the License for the specific language governing rights and 24 * limitations under the License. 25 * 26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ 27 */ 28 29 #ifndef _KERN_LOCK_ATTR_H_ 30 #define _KERN_LOCK_ATTR_H_ 31 32 #include <kern/lock_types.h> 33 34 __BEGIN_DECLS 35 36 #ifdef XNU_KERNEL_PRIVATE 37 typedef struct _lck_attr_ { 38 unsigned int lck_attr_val; 39 } lck_attr_t; 40 41 extern lck_attr_t LockDefaultLckAttr; 42 43 #define LCK_ATTR_NONE 0 44 #define LCK_ATTR_DEBUG 0x00000001 45 #define LCK_ATTR_RW_SHARED_PRIORITY 0x00010000 46 #else /* !XNU_KERNEL_PRIVATE */ 47 typedef struct __lck_attr__ lck_attr_t; 48 #endif /* !XNU_KERNEL_PRIVATE */ 49 50 #define LCK_ATTR_NULL ((lck_attr_t *)NULL) 51 52 extern lck_attr_t *lck_attr_alloc_init(void); 53 54 extern void lck_attr_setdefault( 55 lck_attr_t *attr); 56 57 extern void lck_attr_setdebug( 58 lck_attr_t *attr); 59 60 extern void lck_attr_cleardebug( 61 lck_attr_t *attr); 62 63 extern void lck_attr_free( 64 lck_attr_t *attr); 65 66 #ifdef XNU_KERNEL_PRIVATE 67 /*! 68 * @function lck_attr_rw_shared_priority 69 * 70 * @abstract 71 * Changes the rw lock behaviour by setting reader priority over writer. 72 * 73 * @discussion 74 * The attribute needs to be set before calling lck_rw_init(). 75 * This attribute changes the locking behaviour by possibly starving the writers. 76 * Readers will always be able to lock the lock as long as a writer is not holding it. 77 * This attribute was added to allow recursive locking in shared mode. 78 * 79 * @param attr attr to modify 80 */ 81 extern void lck_attr_rw_shared_priority( 82 lck_attr_t *attr); 83 #endif /* XNU_KERNEL_PRIVATE */ 84 85 __END_DECLS 86 87 #endif /* _KERN_LOCK_ATTR_H_ */ 88