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, Version 1.0 only 6 * (the "License"). You may not use this file except in compliance 7 * with the License. 8 * 9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 10 * or http://www.opensolaris.org/os/licensing. 11 * See the License for the specific language governing permissions 12 * and limitations under the License. 13 * 14 * When distributing Covered Code, include this CDDL HEADER in each 15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 16 * If applicable, add the following below this CDDL HEADER, with the 17 * fields enclosed by brackets "[]" replaced with your own identifying 18 * information: Portions Copyright [yyyy] [name of copyright owner] 19 * 20 * CDDL HEADER END 21 */ 22 /* 23 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 24 * Use is subject to license terms. 25 */ 26 27 #pragma ident "%Z%%M% %I% %E% SMI" 28 29 #include <sys/types.h> 30 #include <sys/id_space.h> 31 #include <sys/debug.h> 32 33 /* 34 * ID Spaces 35 * 36 * The id_space_t provides a simple implementation of a managed range of 37 * integer identifiers using a vmem arena. An ID space guarantees that the 38 * next identifer returned by an allocation is larger than the previous one, 39 * unless there are no larger slots remaining in the range. In this case, 40 * the ID space will return the first available slot in the lower part of the 41 * range (viewing the previous identifier as a partitioning element). If no 42 * slots are available, id_alloc() will sleep until an identifier becomes 43 * available. Accordingly, id_space allocations must be initiated from 44 * contexts where sleeping is acceptable. id_alloc_nosleep() will return 45 * -1 if no slots are available or if the system is low on memory. If 46 * id_alloc_nosleep() fails, callers should not try to extend the ID 47 * space. This is to avoid making a possible low-memory situation 48 * worse. 49 * 50 * As an ID space is designed for representing a range of id_t's, there 51 * is a preexisting maximal range: [0, MAXUID]. ID space requests 52 * outside that range will fail on a DEBUG kernel. 53 * 54 * (Presently, the id_space_t abstraction supports only direct allocations; ID 55 * reservation, in which an ID is allocated but placed in a internal 56 * dictionary for later use, should be added when a consuming subsystem 57 * arrives.) 58 */ 59 60 /* 61 * Create an arena to represent the range [low, high). 62 * Caller must be in a context in which VM_SLEEP is legal. 63 */ 64 id_space_t * 65 id_space_create(const char *name, id_t low, id_t high) 66 { 67 ASSERT(low >= 0); 68 ASSERT(low < high); 69 70 return (vmem_create(name, (void *)(uintptr_t)(low + 1), high - low, 1, 71 NULL, NULL, NULL, 0, VM_SLEEP | VMC_IDENTIFIER)); 72 } 73 74 /* 75 * Destroy a previously created ID space. 76 * No restrictions on caller's context. 77 */ 78 void 79 id_space_destroy(id_space_t *isp) 80 { 81 vmem_destroy(isp); 82 } 83 84 void 85 id_space_extend(id_space_t *isp, id_t low, id_t high) 86 { 87 (void) vmem_add(isp, 88 (void *)(uintptr_t)(low + 1), high - low, VM_SLEEP); 89 } 90 91 /* 92 * Allocate an id_t from specified ID space. 93 * Caller must be in a context in which VM_SLEEP is legal. 94 */ 95 id_t 96 id_alloc(id_space_t *isp) 97 { 98 return ((id_t)(uintptr_t) 99 vmem_alloc(isp, 1, VM_SLEEP | VM_NEXTFIT) - 1); 100 } 101 102 /* 103 * Allocate an id_t from specified ID space. 104 * Returns -1 on failure (see module block comments for more information on 105 * failure modes). 106 */ 107 id_t 108 id_alloc_nosleep(id_space_t *isp) 109 { 110 return ((id_t)(uintptr_t) 111 vmem_alloc(isp, 1, VM_NOSLEEP | VM_NEXTFIT) - 1); 112 } 113 114 /* 115 * Free a previously allocated ID. 116 * No restrictions on caller's context. 117 */ 118 void 119 id_free(id_space_t *isp, id_t id) 120 { 121 vmem_free(isp, (void *)(uintptr_t)(id + 1), 1); 122 } 123