1/* SPDX-License-Identifier: GPL-2.0 OR MIT */
  2/**************************************************************************
  3 *
  4 * Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
  5 * All Rights Reserved.
  6 *
  7 * Permission is hereby granted, free of charge, to any person obtaining a
  8 * copy of this software and associated documentation files (the
  9 * "Software"), to deal in the Software without restriction, including
 10 * without limitation the rights to use, copy, modify, merge, publish,
 11 * distribute, sub license, and/or sell copies of the Software, and to
 12 * permit persons to whom the Software is furnished to do so, subject to
 13 * the following conditions:
 14 *
 15 * The above copyright notice and this permission notice (including the
 16 * next paragraph) shall be included in all copies or substantial portions
 17 * of the Software.
 18 *
 19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 20 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 21 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 22 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
 23 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 24 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 25 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 26 *
 27 **************************************************************************/
 28/*
 29 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
 30 */
 31
 32#include <linux/atomic.h>
 33#include <linux/errno.h>
 34#include <linux/wait.h>
 35#include <linux/sched/signal.h>
 36#include "ttm_lock.h"
 37#include "ttm_object.h"
 38
 39#define TTM_WRITE_LOCK_PENDING    (1 << 0)
 40#define TTM_VT_LOCK_PENDING       (1 << 1)
 41#define TTM_SUSPEND_LOCK_PENDING  (1 << 2)
 42#define TTM_VT_LOCK               (1 << 3)
 43#define TTM_SUSPEND_LOCK          (1 << 4)
 44
 45void ttm_lock_init(struct ttm_lock *lock)
 46{
 47	spin_lock_init(&lock->lock);
 48	init_waitqueue_head(&lock->queue);
 49	lock->rw = 0;
 50	lock->flags = 0;
 51}
 52
 53void ttm_read_unlock(struct ttm_lock *lock)
 54{
 55	spin_lock(&lock->lock);
 56	if (--lock->rw == 0)
 57		wake_up_all(&lock->queue);
 58	spin_unlock(&lock->lock);
 59}
 60
 61static bool __ttm_read_lock(struct ttm_lock *lock)
 62{
 63	bool locked = false;
 64
 65	spin_lock(&lock->lock);
 66	if (lock->rw >= 0 && lock->flags == 0) {
 67		++lock->rw;
 68		locked = true;
 69	}
 70	spin_unlock(&lock->lock);
 71	return locked;
 72}
 73
 74int ttm_read_lock(struct ttm_lock *lock, bool interruptible)
 75{
 76	int ret = 0;
 77
 78	if (interruptible)
 79		ret = wait_event_interruptible(lock->queue,
 80					       __ttm_read_lock(lock));
 81	else
 82		wait_event(lock->queue, __ttm_read_lock(lock));
 83	return ret;
 84}
 85
 86static bool __ttm_read_trylock(struct ttm_lock *lock, bool *locked)
 87{
 88	bool block = true;
 89
 90	*locked = false;
 91
 92	spin_lock(&lock->lock);
 93	if (lock->rw >= 0 && lock->flags == 0) {
 94		++lock->rw;
 95		block = false;
 96		*locked = true;
 97	} else if (lock->flags == 0) {
 98		block = false;
 99	}
100	spin_unlock(&lock->lock);
101
102	return !block;
103}
104
105int ttm_read_trylock(struct ttm_lock *lock, bool interruptible)
106{
107	int ret = 0;
108	bool locked;
109
110	if (interruptible)
111		ret = wait_event_interruptible
112			(lock->queue, __ttm_read_trylock(lock, &locked));
113	else
114		wait_event(lock->queue, __ttm_read_trylock(lock, &locked));
115
116	if (unlikely(ret != 0)) {
117		BUG_ON(locked);
118		return ret;
119	}
120
121	return (locked) ? 0 : -EBUSY;
122}
123
124void ttm_write_unlock(struct ttm_lock *lock)
125{
126	spin_lock(&lock->lock);
127	lock->rw = 0;
128	wake_up_all(&lock->queue);
129	spin_unlock(&lock->lock);
130}
131
132static bool __ttm_write_lock(struct ttm_lock *lock)
133{
134	bool locked = false;
135
136	spin_lock(&lock->lock);
137	if (lock->rw == 0 && ((lock->flags & ~TTM_WRITE_LOCK_PENDING) == 0)) {
138		lock->rw = -1;
139		lock->flags &= ~TTM_WRITE_LOCK_PENDING;
140		locked = true;
141	} else {
142		lock->flags |= TTM_WRITE_LOCK_PENDING;
143	}
144	spin_unlock(&lock->lock);
145	return locked;
146}
147
148int ttm_write_lock(struct ttm_lock *lock, bool interruptible)
149{
150	int ret = 0;
151
152	if (interruptible) {
153		ret = wait_event_interruptible(lock->queue,
154					       __ttm_write_lock(lock));
155		if (unlikely(ret != 0)) {
156			spin_lock(&lock->lock);
157			lock->flags &= ~TTM_WRITE_LOCK_PENDING;
158			wake_up_all(&lock->queue);
159			spin_unlock(&lock->lock);
160		}
161	} else
162		wait_event(lock->queue, __ttm_write_lock(lock));
163
164	return ret;
165}
166
167void ttm_suspend_unlock(struct ttm_lock *lock)
168{
169	spin_lock(&lock->lock);
170	lock->flags &= ~TTM_SUSPEND_LOCK;
171	wake_up_all(&lock->queue);
172	spin_unlock(&lock->lock);
173}
174
175static bool __ttm_suspend_lock(struct ttm_lock *lock)
176{
177	bool locked = false;
178
179	spin_lock(&lock->lock);
180	if (lock->rw == 0) {
181		lock->flags &= ~TTM_SUSPEND_LOCK_PENDING;
182		lock->flags |= TTM_SUSPEND_LOCK;
183		locked = true;
184	} else {
185		lock->flags |= TTM_SUSPEND_LOCK_PENDING;
186	}
187	spin_unlock(&lock->lock);
188	return locked;
189}
190
191void ttm_suspend_lock(struct ttm_lock *lock)
192{
193	wait_event(lock->queue, __ttm_suspend_lock(lock));
194}