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  2 *
  3 * Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
  4 * All Rights Reserved.
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  6 * Permission is hereby granted, free of charge, to any person obtaining a
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 11 * permit persons to whom the Software is furnished to do so, subject to
 12 * the following conditions:
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 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.
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 19 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 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
 68struct 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 */
 83extern 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 */
 92extern 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 */
104extern 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 */
121extern 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 */
130extern 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 */
142extern 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 */
151extern 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 */
160extern 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 */
169extern 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 */
183extern 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 */
195extern 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 */
204extern 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 */
216extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
217
218#endif