1 /* $NetBSD: ttm_lock.h,v 1.2 2021/12/18 23:45:45 riastradh Exp $ */ 2 3 /************************************************************************** 4 * 5 * Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA 6 * All Rights Reserved. 7 * 8 * Permission is hereby granted, free of charge, to any person obtaining a 9 * copy of this software and associated documentation files (the 10 * "Software"), to deal in the Software without restriction, including 11 * without limitation the rights to use, copy, modify, merge, publish, 12 * distribute, sub license, and/or sell copies of the Software, and to 13 * permit persons to whom the Software is furnished to do so, subject to 14 * the following conditions: 15 * 16 * The above copyright notice and this permission notice (including the 17 * next paragraph) shall be included in all copies or substantial portions 18 * of the Software. 19 * 20 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 21 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 22 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL 23 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, 24 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR 25 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE 26 * USE OR OTHER DEALINGS IN THE SOFTWARE. 27 * 28 **************************************************************************/ 29 /* 30 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com> 31 */ 32 33 /** @file ttm_lock.h 34 * This file implements a simple replacement for the buffer manager use 35 * of the DRM heavyweight hardware lock. 36 * The lock is a read-write lock. Taking it in read mode and write mode 37 * is relatively fast, and intended for in-kernel use only. 38 * 39 * The vt mode is used only when there is a need to block all 40 * user-space processes from validating buffers. 41 * It's allowed to leave kernel space with the vt lock held. 42 * If a user-space process dies while having the vt-lock, 43 * it will be released during the file descriptor release. The vt lock 44 * excludes write lock and read lock. 45 * 46 * The suspend mode is used to lock out all TTM users when preparing for 47 * and executing suspend operations. 48 * 49 */ 50 51 #ifndef _TTM_LOCK_H_ 52 #define _TTM_LOCK_H_ 53 54 #include <linux/atomic.h> 55 #include <linux/wait.h> 56 57 #include "ttm_object.h" 58 59 /** 60 * struct ttm_lock 61 * 62 * @base: ttm base object used solely to release the lock if the client 63 * holding the lock dies. 64 * @queue: Queue for processes waiting for lock change-of-status. 65 * @lock: Spinlock protecting some lock members. 66 * @rw: Read-write lock counter. Protected by @lock. 67 * @flags: Lock state. Protected by @lock. 68 */ 69 70 struct ttm_lock { 71 struct ttm_base_object base; 72 wait_queue_head_t queue; 73 spinlock_t lock; 74 int32_t rw; 75 uint32_t flags; 76 }; 77 78 79 /** 80 * ttm_lock_init 81 * 82 * @lock: Pointer to a struct ttm_lock 83 * Initializes the lock. 84 */ 85 extern void ttm_lock_init(struct ttm_lock *lock); 86 87 /** 88 * ttm_read_unlock 89 * 90 * @lock: Pointer to a struct ttm_lock 91 * 92 * Releases a read lock. 93 */ 94 extern void ttm_read_unlock(struct ttm_lock *lock); 95 96 /** 97 * ttm_read_lock 98 * 99 * @lock: Pointer to a struct ttm_lock 100 * @interruptible: Interruptible sleeping while waiting for a lock. 101 * 102 * Takes the lock in read mode. 103 * Returns: 104 * -ERESTARTSYS If interrupted by a signal and interruptible is true. 105 */ 106 extern int ttm_read_lock(struct ttm_lock *lock, bool interruptible); 107 108 /** 109 * ttm_read_trylock 110 * 111 * @lock: Pointer to a struct ttm_lock 112 * @interruptible: Interruptible sleeping while waiting for a lock. 113 * 114 * Tries to take the lock in read mode. If the lock is already held 115 * in write mode, the function will return -EBUSY. If the lock is held 116 * in vt or suspend mode, the function will sleep until these modes 117 * are unlocked. 118 * 119 * Returns: 120 * -EBUSY The lock was already held in write mode. 121 * -ERESTARTSYS If interrupted by a signal and interruptible is true. 122 */ 123 extern int ttm_read_trylock(struct ttm_lock *lock, bool interruptible); 124 125 /** 126 * ttm_write_unlock 127 * 128 * @lock: Pointer to a struct ttm_lock 129 * 130 * Releases a write lock. 131 */ 132 extern void ttm_write_unlock(struct ttm_lock *lock); 133 134 /** 135 * ttm_write_lock 136 * 137 * @lock: Pointer to a struct ttm_lock 138 * @interruptible: Interruptible sleeping while waiting for a lock. 139 * 140 * Takes the lock in write mode. 141 * Returns: 142 * -ERESTARTSYS If interrupted by a signal and interruptible is true. 143 */ 144 extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible); 145 146 /** 147 * ttm_lock_downgrade 148 * 149 * @lock: Pointer to a struct ttm_lock 150 * 151 * Downgrades a write lock to a read lock. 152 */ 153 extern void ttm_lock_downgrade(struct ttm_lock *lock); 154 155 /** 156 * ttm_suspend_lock 157 * 158 * @lock: Pointer to a struct ttm_lock 159 * 160 * Takes the lock in suspend mode. Excludes read and write mode. 161 */ 162 extern void ttm_suspend_lock(struct ttm_lock *lock); 163 164 /** 165 * ttm_suspend_unlock 166 * 167 * @lock: Pointer to a struct ttm_lock 168 * 169 * Releases a suspend lock 170 */ 171 extern void ttm_suspend_unlock(struct ttm_lock *lock); 172 173 /** 174 * ttm_vt_lock 175 * 176 * @lock: Pointer to a struct ttm_lock 177 * @interruptible: Interruptible sleeping while waiting for a lock. 178 * @tfile: Pointer to a struct ttm_object_file to register the lock with. 179 * 180 * Takes the lock in vt mode. 181 * Returns: 182 * -ERESTARTSYS If interrupted by a signal and interruptible is true. 183 * -ENOMEM: Out of memory when locking. 184 */ 185 extern int ttm_vt_lock(struct ttm_lock *lock, bool interruptible, 186 struct ttm_object_file *tfile); 187 188 /** 189 * ttm_vt_unlock 190 * 191 * @lock: Pointer to a struct ttm_lock 192 * 193 * Releases a vt lock. 194 * Returns: 195 * -EINVAL If the lock was not held. 196 */ 197 extern int ttm_vt_unlock(struct ttm_lock *lock); 198 199 /** 200 * ttm_write_unlock 201 * 202 * @lock: Pointer to a struct ttm_lock 203 * 204 * Releases a write lock. 205 */ 206 extern void ttm_write_unlock(struct ttm_lock *lock); 207 208 /** 209 * ttm_write_lock 210 * 211 * @lock: Pointer to a struct ttm_lock 212 * @interruptible: Interruptible sleeping while waiting for a lock. 213 * 214 * Takes the lock in write mode. 215 * Returns: 216 * -ERESTARTSYS If interrupted by a signal and interruptible is true. 217 */ 218 extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible); 219 220 #endif 221