Merge branch 'swiotlb' of git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux-2.6
[linux-2.6] / drivers / char / drm / drm_lock.c
1 /**
2  * \file drm_lock.c
3  * IOCTLs for locking
4  *
5  * \author Rickard E. (Rik) Faith <faith@valinux.com>
6  * \author Gareth Hughes <gareth@valinux.com>
7  */
8
9 /*
10  * Created: Tue Feb  2 08:37:54 1999 by faith@valinux.com
11  *
12  * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas.
13  * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California.
14  * All Rights Reserved.
15  *
16  * Permission is hereby granted, free of charge, to any person obtaining a
17  * copy of this software and associated documentation files (the "Software"),
18  * to deal in the Software without restriction, including without limitation
19  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
20  * and/or sell copies of the Software, and to permit persons to whom the
21  * Software is furnished to do so, subject to the following conditions:
22  *
23  * The above copyright notice and this permission notice (including the next
24  * paragraph) shall be included in all copies or substantial portions of the
25  * Software.
26  *
27  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
28  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
29  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
30  * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
31  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
32  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
33  * OTHER DEALINGS IN THE SOFTWARE.
34  */
35
36 #include "drmP.h"
37
38 static int drm_lock_transfer(drm_device_t * dev,
39                              __volatile__ unsigned int *lock,
40                              unsigned int context);
41 static int drm_notifier(void *priv);
42
43 /**
44  * Lock ioctl.
45  *
46  * \param inode device inode.
47  * \param filp file pointer.
48  * \param cmd command.
49  * \param arg user argument, pointing to a drm_lock structure.
50  * \return zero on success or negative number on failure.
51  *
52  * Add the current task to the lock wait queue, and attempt to take to lock.
53  */
54 int drm_lock(struct inode *inode, struct file *filp,
55              unsigned int cmd, unsigned long arg)
56 {
57         drm_file_t *priv = filp->private_data;
58         drm_device_t *dev = priv->head->dev;
59         DECLARE_WAITQUEUE(entry, current);
60         drm_lock_t lock;
61         int ret = 0;
62
63         ++priv->lock_count;
64
65         if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
66                 return -EFAULT;
67
68         if (lock.context == DRM_KERNEL_CONTEXT) {
69                 DRM_ERROR("Process %d using kernel context %d\n",
70                           current->pid, lock.context);
71                 return -EINVAL;
72         }
73
74         DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
75                   lock.context, current->pid,
76                   dev->lock.hw_lock->lock, lock.flags);
77
78         if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE))
79                 if (lock.context < 0)
80                         return -EINVAL;
81
82         add_wait_queue(&dev->lock.lock_queue, &entry);
83         for (;;) {
84                 __set_current_state(TASK_INTERRUPTIBLE);
85                 if (!dev->lock.hw_lock) {
86                         /* Device has been unregistered */
87                         ret = -EINTR;
88                         break;
89                 }
90                 if (drm_lock_take(&dev->lock.hw_lock->lock, lock.context)) {
91                         dev->lock.filp = filp;
92                         dev->lock.lock_time = jiffies;
93                         atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
94                         break;  /* Got lock */
95                 }
96
97                 /* Contention */
98                 schedule();
99                 if (signal_pending(current)) {
100                         ret = -ERESTARTSYS;
101                         break;
102                 }
103         }
104         __set_current_state(TASK_RUNNING);
105         remove_wait_queue(&dev->lock.lock_queue, &entry);
106
107         sigemptyset(&dev->sigmask);
108         sigaddset(&dev->sigmask, SIGSTOP);
109         sigaddset(&dev->sigmask, SIGTSTP);
110         sigaddset(&dev->sigmask, SIGTTIN);
111         sigaddset(&dev->sigmask, SIGTTOU);
112         dev->sigdata.context = lock.context;
113         dev->sigdata.lock = dev->lock.hw_lock;
114         block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
115
116         if (dev->driver->dma_ready && (lock.flags & _DRM_LOCK_READY))
117                 dev->driver->dma_ready(dev);
118
119         if (dev->driver->dma_quiescent && (lock.flags & _DRM_LOCK_QUIESCENT))
120                 return dev->driver->dma_quiescent(dev);
121
122         /* dev->driver->kernel_context_switch isn't used by any of the x86
123          *  drivers but is used by the Sparc driver.
124          */
125
126         if (dev->driver->kernel_context_switch &&
127             dev->last_context != lock.context) {
128                 dev->driver->kernel_context_switch(dev, dev->last_context,
129                                                    lock.context);
130         }
131         DRM_DEBUG("%d %s\n", lock.context, ret ? "interrupted" : "has lock");
132
133         return ret;
134 }
135
136 /**
137  * Unlock ioctl.
138  *
139  * \param inode device inode.
140  * \param filp file pointer.
141  * \param cmd command.
142  * \param arg user argument, pointing to a drm_lock structure.
143  * \return zero on success or negative number on failure.
144  *
145  * Transfer and free the lock.
146  */
147 int drm_unlock(struct inode *inode, struct file *filp,
148                unsigned int cmd, unsigned long arg)
149 {
150         drm_file_t *priv = filp->private_data;
151         drm_device_t *dev = priv->head->dev;
152         drm_lock_t lock;
153
154         if (copy_from_user(&lock, (drm_lock_t __user *) arg, sizeof(lock)))
155                 return -EFAULT;
156
157         if (lock.context == DRM_KERNEL_CONTEXT) {
158                 DRM_ERROR("Process %d using kernel context %d\n",
159                           current->pid, lock.context);
160                 return -EINVAL;
161         }
162
163         atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
164
165         /* kernel_context_switch isn't used by any of the x86 drm
166          * modules but is required by the Sparc driver.
167          */
168         if (dev->driver->kernel_context_switch_unlock)
169                 dev->driver->kernel_context_switch_unlock(dev, &lock);
170         else {
171                 drm_lock_transfer(dev, &dev->lock.hw_lock->lock,
172                                   DRM_KERNEL_CONTEXT);
173
174                 if (drm_lock_free(dev, &dev->lock.hw_lock->lock,
175                                   DRM_KERNEL_CONTEXT)) {
176                         DRM_ERROR("\n");
177                 }
178         }
179
180         unblock_all_signals();
181         return 0;
182 }
183
184 /**
185  * Take the heavyweight lock.
186  *
187  * \param lock lock pointer.
188  * \param context locking context.
189  * \return one if the lock is held, or zero otherwise.
190  *
191  * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
192  */
193 int drm_lock_take(__volatile__ unsigned int *lock, unsigned int context)
194 {
195         unsigned int old, new, prev;
196
197         do {
198                 old = *lock;
199                 if (old & _DRM_LOCK_HELD)
200                         new = old | _DRM_LOCK_CONT;
201                 else
202                         new = context | _DRM_LOCK_HELD;
203                 prev = cmpxchg(lock, old, new);
204         } while (prev != old);
205         if (_DRM_LOCKING_CONTEXT(old) == context) {
206                 if (old & _DRM_LOCK_HELD) {
207                         if (context != DRM_KERNEL_CONTEXT) {
208                                 DRM_ERROR("%d holds heavyweight lock\n",
209                                           context);
210                         }
211                         return 0;
212                 }
213         }
214         if (new == (context | _DRM_LOCK_HELD)) {
215                 /* Have lock */
216                 return 1;
217         }
218         return 0;
219 }
220
221 /**
222  * This takes a lock forcibly and hands it to context.  Should ONLY be used
223  * inside *_unlock to give lock to kernel before calling *_dma_schedule.
224  *
225  * \param dev DRM device.
226  * \param lock lock pointer.
227  * \param context locking context.
228  * \return always one.
229  *
230  * Resets the lock file pointer.
231  * Marks the lock as held by the given context, via the \p cmpxchg instruction.
232  */
233 static int drm_lock_transfer(drm_device_t * dev,
234                              __volatile__ unsigned int *lock,
235                              unsigned int context)
236 {
237         unsigned int old, new, prev;
238
239         dev->lock.filp = NULL;
240         do {
241                 old = *lock;
242                 new = context | _DRM_LOCK_HELD;
243                 prev = cmpxchg(lock, old, new);
244         } while (prev != old);
245         return 1;
246 }
247
248 /**
249  * Free lock.
250  *
251  * \param dev DRM device.
252  * \param lock lock.
253  * \param context context.
254  *
255  * Resets the lock file pointer.
256  * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
257  * waiting on the lock queue.
258  */
259 int drm_lock_free(drm_device_t * dev,
260                   __volatile__ unsigned int *lock, unsigned int context)
261 {
262         unsigned int old, new, prev;
263
264         dev->lock.filp = NULL;
265         do {
266                 old = *lock;
267                 new = 0;
268                 prev = cmpxchg(lock, old, new);
269         } while (prev != old);
270         if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
271                 DRM_ERROR("%d freed heavyweight lock held by %d\n",
272                           context, _DRM_LOCKING_CONTEXT(old));
273                 return 1;
274         }
275         wake_up_interruptible(&dev->lock.lock_queue);
276         return 0;
277 }
278
279 /**
280  * If we get here, it means that the process has called DRM_IOCTL_LOCK
281  * without calling DRM_IOCTL_UNLOCK.
282  *
283  * If the lock is not held, then let the signal proceed as usual.  If the lock
284  * is held, then set the contended flag and keep the signal blocked.
285  *
286  * \param priv pointer to a drm_sigdata structure.
287  * \return one if the signal should be delivered normally, or zero if the
288  * signal should be blocked.
289  */
290 static int drm_notifier(void *priv)
291 {
292         drm_sigdata_t *s = (drm_sigdata_t *) priv;
293         unsigned int old, new, prev;
294
295         /* Allow signal delivery if lock isn't held */
296         if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
297             || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
298                 return 1;
299
300         /* Otherwise, set flag to force call to
301            drmUnlock */
302         do {
303                 old = s->lock->lock;
304                 new = old | _DRM_LOCK_CONT;
305                 prev = cmpxchg(&s->lock->lock, old, new);
306         } while (prev != old);
307         return 0;
308 }