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  3 * Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
  4 * All Rights Reserved.
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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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 15 * next paragraph) shall be included in all copies or substantial portions
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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/wait.h>
 53#include <linux/atomic.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 * @kill_takers: Boolean whether to kill takers of the lock.
 67 * @signal: Signal to send when kill_takers is true.
 68 */
 69
 70struct 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	bool kill_takers;
 77	int signal;
 78	struct ttm_object_file *vt_holder;
 79};
 80
 81
 82/**
 83 * ttm_lock_init
 84 *
 85 * @lock: Pointer to a struct ttm_lock
 86 * Initializes the lock.
 87 */
 88extern void ttm_lock_init(struct ttm_lock *lock);
 89
 90/**
 91 * ttm_read_unlock
 92 *
 93 * @lock: Pointer to a struct ttm_lock
 94 *
 95 * Releases a read lock.
 96 */
 97extern void ttm_read_unlock(struct ttm_lock *lock);
 98
 99/**
100 * ttm_read_lock
101 *
102 * @lock: Pointer to a struct ttm_lock
103 * @interruptible: Interruptible sleeping while waiting for a lock.
104 *
105 * Takes the lock in read mode.
106 * Returns:
107 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
108 */
109extern int ttm_read_lock(struct ttm_lock *lock, bool interruptible);
110
111/**
112 * ttm_read_trylock
113 *
114 * @lock: Pointer to a struct ttm_lock
115 * @interruptible: Interruptible sleeping while waiting for a lock.
116 *
117 * Tries to take the lock in read mode. If the lock is already held
118 * in write mode, the function will return -EBUSY. If the lock is held
119 * in vt or suspend mode, the function will sleep until these modes
120 * are unlocked.
121 *
122 * Returns:
123 * -EBUSY The lock was already held in write mode.
124 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
125 */
126extern int ttm_read_trylock(struct ttm_lock *lock, bool interruptible);
127
128/**
129 * ttm_write_unlock
130 *
131 * @lock: Pointer to a struct ttm_lock
132 *
133 * Releases a write lock.
134 */
135extern void ttm_write_unlock(struct ttm_lock *lock);
136
137/**
138 * ttm_write_lock
139 *
140 * @lock: Pointer to a struct ttm_lock
141 * @interruptible: Interruptible sleeping while waiting for a lock.
142 *
143 * Takes the lock in write mode.
144 * Returns:
145 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
146 */
147extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
148
149/**
150 * ttm_lock_downgrade
151 *
152 * @lock: Pointer to a struct ttm_lock
153 *
154 * Downgrades a write lock to a read lock.
155 */
156extern void ttm_lock_downgrade(struct ttm_lock *lock);
157
158/**
159 * ttm_suspend_lock
160 *
161 * @lock: Pointer to a struct ttm_lock
162 *
163 * Takes the lock in suspend mode. Excludes read and write mode.
164 */
165extern void ttm_suspend_lock(struct ttm_lock *lock);
166
167/**
168 * ttm_suspend_unlock
169 *
170 * @lock: Pointer to a struct ttm_lock
171 *
172 * Releases a suspend lock
173 */
174extern void ttm_suspend_unlock(struct ttm_lock *lock);
175
176/**
177 * ttm_vt_lock
178 *
179 * @lock: Pointer to a struct ttm_lock
180 * @interruptible: Interruptible sleeping while waiting for a lock.
181 * @tfile: Pointer to a struct ttm_object_file to register the lock with.
182 *
183 * Takes the lock in vt mode.
184 * Returns:
185 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
186 * -ENOMEM: Out of memory when locking.
187 */
188extern int ttm_vt_lock(struct ttm_lock *lock, bool interruptible,
189		       struct ttm_object_file *tfile);
190
191/**
192 * ttm_vt_unlock
193 *
194 * @lock: Pointer to a struct ttm_lock
195 *
196 * Releases a vt lock.
197 * Returns:
198 * -EINVAL If the lock was not held.
199 */
200extern int ttm_vt_unlock(struct ttm_lock *lock);
201
202/**
203 * ttm_write_unlock
204 *
205 * @lock: Pointer to a struct ttm_lock
206 *
207 * Releases a write lock.
208 */
209extern void ttm_write_unlock(struct ttm_lock *lock);
210
211/**
212 * ttm_write_lock
213 *
214 * @lock: Pointer to a struct ttm_lock
215 * @interruptible: Interruptible sleeping while waiting for a lock.
216 *
217 * Takes the lock in write mode.
218 * Returns:
219 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
220 */
221extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
222
223/**
224 * ttm_lock_set_kill
225 *
226 * @lock: Pointer to a struct ttm_lock
227 * @val: Boolean whether to kill processes taking the lock.
228 * @signal: Signal to send to the process taking the lock.
229 *
230 * The kill-when-taking-lock functionality is used to kill processes that keep
231 * on using the TTM functionality when its resources has been taken down, for
232 * example when the X server exits. A typical sequence would look like this:
233 * - X server takes lock in write mode.
234 * - ttm_lock_set_kill() is called with @val set to true.
235 * - As part of X server exit, TTM resources are taken down.
236 * - X server releases the lock on file release.
237 * - Another dri client wants to render, takes the lock and is killed.
238 *
239 */
240static inline void ttm_lock_set_kill(struct ttm_lock *lock, bool val,
241				     int signal)
242{
243	lock->kill_takers = val;
244	if (val)
245		lock->signal = signal;
246}
247
248#endif