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