drm_lock.c revision 302408 
1/*-
2 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
3 * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
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 "Software"),
8 * to deal in the Software without restriction, including without limitation
9 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10 * and/or sell copies of the Software, and to permit persons to whom the
11 * Software is furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice (including the next
14 * paragraph) shall be included in all copies or substantial portions of the
15 * Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
20 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
21 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
22 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
23 * OTHER DEALINGS IN THE SOFTWARE.
24 *
25 * Authors:
26 *    Rickard E. (Rik) Faith <faith@valinux.com>
27 *    Gareth Hughes <gareth@valinux.com>
28 *
29 */
30
31#include <sys/cdefs.h>
32__FBSDID("$FreeBSD: stable/11/sys/dev/drm/drm_lock.c 190023 2009-03-19 08:36:08Z rnoland $");
33
34/** @file drm_lock.c
35 * Implementation of the ioctls and other support code for dealing with the
36 * hardware lock.
37 *
38 * The DRM hardware lock is a shared structure between the kernel and userland.
39 *
40 * On uncontended access where the new context was the last context, the
41 * client may take the lock without dropping down into the kernel, using atomic
42 * compare-and-set.
43 *
44 * If the client finds during compare-and-set that it was not the last owner
45 * of the lock, it calls the DRM lock ioctl, which may sleep waiting for the
46 * lock, and may have side-effects of kernel-managed context switching.
47 *
48 * When the client releases the lock, if the lock is marked as being contended
49 * by another client, then the DRM unlock ioctl is called so that the
50 * contending client may be woken up.
51 */
52
53#include "dev/drm/drmP.h"
54
55int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
56{
57	struct drm_lock *lock = data;
58	int ret = 0;
59
60	if (lock->context == DRM_KERNEL_CONTEXT) {
61		DRM_ERROR("Process %d using kernel context %d\n",
62		    DRM_CURRENTPID, lock->context);
63		return EINVAL;
64	}
65
66	DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
67	    lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock,
68	    lock->flags);
69
70	if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE) &&
71	    lock->context < 0)
72		return EINVAL;
73
74	DRM_LOCK();
75	for (;;) {
76		if (drm_lock_take(&dev->lock, lock->context)) {
77			dev->lock.file_priv = file_priv;
78			dev->lock.lock_time = jiffies;
79			atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
80			break;  /* Got lock */
81		}
82
83		/* Contention */
84		ret = mtx_sleep((void *)&dev->lock.lock_queue, &dev->dev_lock,
85		    PCATCH, "drmlk2", 0);
86		if (ret != 0)
87			break;
88	}
89	DRM_UNLOCK();
90
91	if (ret == ERESTART)
92		DRM_DEBUG("restarting syscall\n");
93	else
94		DRM_DEBUG("%d %s\n", lock->context,
95		    ret ? "interrupted" : "has lock");
96
97	if (ret != 0)
98		return ret;
99
100	/* XXX: Add signal blocking here */
101
102	if (dev->driver->dma_quiescent != NULL &&
103	    (lock->flags & _DRM_LOCK_QUIESCENT))
104		dev->driver->dma_quiescent(dev);
105
106	return 0;
107}
108
109int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
110{
111	struct drm_lock *lock = data;
112
113	DRM_DEBUG("%d (pid %d) requests unlock (0x%08x), flags = 0x%08x\n",
114	    lock->context, DRM_CURRENTPID, dev->lock.hw_lock->lock,
115	    lock->flags);
116
117	if (lock->context == DRM_KERNEL_CONTEXT) {
118		DRM_ERROR("Process %d using kernel context %d\n",
119		    DRM_CURRENTPID, lock->context);
120		return EINVAL;
121	}
122
123	atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
124
125	DRM_LOCK();
126	drm_lock_transfer(&dev->lock, DRM_KERNEL_CONTEXT);
127
128	if (drm_lock_free(&dev->lock, DRM_KERNEL_CONTEXT)) {
129		DRM_ERROR("\n");
130	}
131	DRM_UNLOCK();
132
133	return 0;
134}
135
136int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context)
137{
138	volatile unsigned int *lock = &lock_data->hw_lock->lock;
139	unsigned int old, new;
140
141	do {
142		old = *lock;
143		if (old & _DRM_LOCK_HELD)
144			new = old | _DRM_LOCK_CONT;
145		else
146			new = context | _DRM_LOCK_HELD;
147	} while (!atomic_cmpset_int(lock, old, new));
148
149	if (_DRM_LOCKING_CONTEXT(old) == context) {
150		if (old & _DRM_LOCK_HELD) {
151			if (context != DRM_KERNEL_CONTEXT) {
152				DRM_ERROR("%d holds heavyweight lock\n",
153				    context);
154			}
155			return 0;
156		}
157	}
158	if (new == (context | _DRM_LOCK_HELD)) {
159		/* Have lock */
160		return 1;
161	}
162	return 0;
163}
164
165/* This takes a lock forcibly and hands it to context.	Should ONLY be used
166   inside *_unlock to give lock to kernel before calling *_dma_schedule. */
167int drm_lock_transfer(struct drm_lock_data *lock_data, unsigned int context)
168{
169	volatile unsigned int *lock = &lock_data->hw_lock->lock;
170	unsigned int old, new;
171
172	lock_data->file_priv = NULL;
173	do {
174		old = *lock;
175		new = context | _DRM_LOCK_HELD;
176	} while (!atomic_cmpset_int(lock, old, new));
177
178	return 1;
179}
180
181int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
182{
183	volatile unsigned int *lock = &lock_data->hw_lock->lock;
184	unsigned int old, new;
185
186	lock_data->file_priv = NULL;
187	do {
188		old = *lock;
189		new = 0;
190	} while (!atomic_cmpset_int(lock, old, new));
191
192	if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
193		DRM_ERROR("%d freed heavyweight lock held by %d\n",
194		    context, _DRM_LOCKING_CONTEXT(old));
195		return 1;
196	}
197	DRM_WAKEUP_INT((void *)&lock_data->lock_queue);
198	return 0;
199}
200