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  4 * All Rights Reserved.
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 11 * permit persons to whom the Software is furnished to do so, subject to
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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 <ttm/ttm_object.h>
 53#include <linux/wait.h>
 54#include <linux/atomic.h>
 55
 56/**
 57 * struct ttm_lock
 58 *
 59 * @base: ttm base object used solely to release the lock if the client
 60 * holding the lock dies.
 61 * @queue: Queue for processes waiting for lock change-of-status.
 62 * @lock: Spinlock protecting some lock members.
 63 * @rw: Read-write lock counter. Protected by @lock.
 64 * @flags: Lock state. Protected by @lock.
 65 * @kill_takers: Boolean whether to kill takers of the lock.
 66 * @signal: Signal to send when kill_takers is true.
 67 */
 68
 69struct ttm_lock {
 70	struct ttm_base_object base;
 71	wait_queue_head_t queue;
 72	spinlock_t lock;
 73	int32_t rw;
 74	uint32_t flags;
 75	bool kill_takers;
 76	int signal;
 77	struct ttm_object_file *vt_holder;
 78};
 79
 80
 81/**
 82 * ttm_lock_init
 83 *
 84 * @lock: Pointer to a struct ttm_lock
 85 * Initializes the lock.
 86 */
 87extern void ttm_lock_init(struct ttm_lock *lock);
 88
 89/**
 90 * ttm_read_unlock
 91 *
 92 * @lock: Pointer to a struct ttm_lock
 93 *
 94 * Releases a read lock.
 95 */
 96extern void ttm_read_unlock(struct ttm_lock *lock);
 97
 98/**
 99 * ttm_read_lock
100 *
101 * @lock: Pointer to a struct ttm_lock
102 * @interruptible: Interruptible sleeping while waiting for a lock.
103 *
104 * Takes the lock in read mode.
105 * Returns:
106 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
107 */
108extern int ttm_read_lock(struct ttm_lock *lock, bool interruptible);
109
110/**
111 * ttm_read_trylock
112 *
113 * @lock: Pointer to a struct ttm_lock
114 * @interruptible: Interruptible sleeping while waiting for a lock.
115 *
116 * Tries to take the lock in read mode. If the lock is already held
117 * in write mode, the function will return -EBUSY. If the lock is held
118 * in vt or suspend mode, the function will sleep until these modes
119 * are unlocked.
120 *
121 * Returns:
122 * -EBUSY The lock was already held in write mode.
123 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
124 */
125extern int ttm_read_trylock(struct ttm_lock *lock, bool interruptible);
126
127/**
128 * ttm_write_unlock
129 *
130 * @lock: Pointer to a struct ttm_lock
131 *
132 * Releases a write lock.
133 */
134extern void ttm_write_unlock(struct ttm_lock *lock);
135
136/**
137 * ttm_write_lock
138 *
139 * @lock: Pointer to a struct ttm_lock
140 * @interruptible: Interruptible sleeping while waiting for a lock.
141 *
142 * Takes the lock in write mode.
143 * Returns:
144 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
145 */
146extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
147
148/**
149 * ttm_lock_downgrade
150 *
151 * @lock: Pointer to a struct ttm_lock
152 *
153 * Downgrades a write lock to a read lock.
154 */
155extern void ttm_lock_downgrade(struct ttm_lock *lock);
156
157/**
158 * ttm_suspend_lock
159 *
160 * @lock: Pointer to a struct ttm_lock
161 *
162 * Takes the lock in suspend mode. Excludes read and write mode.
163 */
164extern void ttm_suspend_lock(struct ttm_lock *lock);
165
166/**
167 * ttm_suspend_unlock
168 *
169 * @lock: Pointer to a struct ttm_lock
170 *
171 * Releases a suspend lock
172 */
173extern void ttm_suspend_unlock(struct ttm_lock *lock);
174
175/**
176 * ttm_vt_lock
177 *
178 * @lock: Pointer to a struct ttm_lock
179 * @interruptible: Interruptible sleeping while waiting for a lock.
180 * @tfile: Pointer to a struct ttm_object_file to register the lock with.
181 *
182 * Takes the lock in vt mode.
183 * Returns:
184 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
185 * -ENOMEM: Out of memory when locking.
186 */
187extern int ttm_vt_lock(struct ttm_lock *lock, bool interruptible,
188		       struct ttm_object_file *tfile);
189
190/**
191 * ttm_vt_unlock
192 *
193 * @lock: Pointer to a struct ttm_lock
194 *
195 * Releases a vt lock.
196 * Returns:
197 * -EINVAL If the lock was not held.
198 */
199extern int ttm_vt_unlock(struct ttm_lock *lock);
200
201/**
202 * ttm_write_unlock
203 *
204 * @lock: Pointer to a struct ttm_lock
205 *
206 * Releases a write lock.
207 */
208extern void ttm_write_unlock(struct ttm_lock *lock);
209
210/**
211 * ttm_write_lock
212 *
213 * @lock: Pointer to a struct ttm_lock
214 * @interruptible: Interruptible sleeping while waiting for a lock.
215 *
216 * Takes the lock in write mode.
217 * Returns:
218 * -ERESTARTSYS If interrupted by a signal and interruptible is true.
219 */
220extern int ttm_write_lock(struct ttm_lock *lock, bool interruptible);
221
222/**
223 * ttm_lock_set_kill
224 *
225 * @lock: Pointer to a struct ttm_lock
226 * @val: Boolean whether to kill processes taking the lock.
227 * @signal: Signal to send to the process taking the lock.
228 *
229 * The kill-when-taking-lock functionality is used to kill processes that keep
230 * on using the TTM functionality when its resources has been taken down, for
231 * example when the X server exits. A typical sequence would look like this:
232 * - X server takes lock in write mode.
233 * - ttm_lock_set_kill() is called with @val set to true.
234 * - As part of X server exit, TTM resources are taken down.
235 * - X server releases the lock on file release.
236 * - Another dri client wants to render, takes the lock and is killed.
237 *
238 */
239static inline void ttm_lock_set_kill(struct ttm_lock *lock, bool val,
240				     int signal)
241{
242	lock->kill_takers = val;
243	if (val)
244		lock->signal = signal;
245}
246
247#endif