Root/drivers/gpu/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 <linux/export.h>
37#include "drmP.h"
38
39static int drm_notifier(void *priv);
40
41static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context);
42
43/**
44 * Lock ioctl.
45 *
46 * \param inode device inode.
47 * \param file_priv DRM file private.
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 */
54int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv)
55{
56    DECLARE_WAITQUEUE(entry, current);
57    struct drm_lock *lock = data;
58    struct drm_master *master = file_priv->master;
59    int ret = 0;
60
61    ++file_priv->lock_count;
62
63    if (lock->context == DRM_KERNEL_CONTEXT) {
64        DRM_ERROR("Process %d using kernel context %d\n",
65              task_pid_nr(current), lock->context);
66        return -EINVAL;
67    }
68
69    DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n",
70          lock->context, task_pid_nr(current),
71          master->lock.hw_lock->lock, lock->flags);
72
73    add_wait_queue(&master->lock.lock_queue, &entry);
74    spin_lock_bh(&master->lock.spinlock);
75    master->lock.user_waiters++;
76    spin_unlock_bh(&master->lock.spinlock);
77
78    for (;;) {
79        __set_current_state(TASK_INTERRUPTIBLE);
80        if (!master->lock.hw_lock) {
81            /* Device has been unregistered */
82            send_sig(SIGTERM, current, 0);
83            ret = -EINTR;
84            break;
85        }
86        if (drm_lock_take(&master->lock, lock->context)) {
87            master->lock.file_priv = file_priv;
88            master->lock.lock_time = jiffies;
89            atomic_inc(&dev->counts[_DRM_STAT_LOCKS]);
90            break; /* Got lock */
91        }
92
93        /* Contention */
94        mutex_unlock(&drm_global_mutex);
95        schedule();
96        mutex_lock(&drm_global_mutex);
97        if (signal_pending(current)) {
98            ret = -EINTR;
99            break;
100        }
101    }
102    spin_lock_bh(&master->lock.spinlock);
103    master->lock.user_waiters--;
104    spin_unlock_bh(&master->lock.spinlock);
105    __set_current_state(TASK_RUNNING);
106    remove_wait_queue(&master->lock.lock_queue, &entry);
107
108    DRM_DEBUG("%d %s\n", lock->context,
109          ret ? "interrupted" : "has lock");
110    if (ret) return ret;
111
112    /* don't set the block all signals on the master process for now
113     * really probably not the correct answer but lets us debug xkb
114      * xserver for now */
115    if (!file_priv->is_master) {
116        sigemptyset(&dev->sigmask);
117        sigaddset(&dev->sigmask, SIGSTOP);
118        sigaddset(&dev->sigmask, SIGTSTP);
119        sigaddset(&dev->sigmask, SIGTTIN);
120        sigaddset(&dev->sigmask, SIGTTOU);
121        dev->sigdata.context = lock->context;
122        dev->sigdata.lock = master->lock.hw_lock;
123        block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask);
124    }
125
126    if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT))
127    {
128        if (dev->driver->dma_quiescent(dev)) {
129            DRM_DEBUG("%d waiting for DMA quiescent\n",
130                  lock->context);
131            return -EBUSY;
132        }
133    }
134
135    return 0;
136}
137
138/**
139 * Unlock ioctl.
140 *
141 * \param inode device inode.
142 * \param file_priv DRM file private.
143 * \param cmd command.
144 * \param arg user argument, pointing to a drm_lock structure.
145 * \return zero on success or negative number on failure.
146 *
147 * Transfer and free the lock.
148 */
149int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv)
150{
151    struct drm_lock *lock = data;
152    struct drm_master *master = file_priv->master;
153
154    if (lock->context == DRM_KERNEL_CONTEXT) {
155        DRM_ERROR("Process %d using kernel context %d\n",
156              task_pid_nr(current), lock->context);
157        return -EINVAL;
158    }
159
160    atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]);
161
162    if (drm_lock_free(&master->lock, lock->context)) {
163        /* FIXME: Should really bail out here. */
164    }
165
166    unblock_all_signals();
167    return 0;
168}
169
170/**
171 * Take the heavyweight lock.
172 *
173 * \param lock lock pointer.
174 * \param context locking context.
175 * \return one if the lock is held, or zero otherwise.
176 *
177 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction.
178 */
179static
180int drm_lock_take(struct drm_lock_data *lock_data,
181          unsigned int context)
182{
183    unsigned int old, new, prev;
184    volatile unsigned int *lock = &lock_data->hw_lock->lock;
185
186    spin_lock_bh(&lock_data->spinlock);
187    do {
188        old = *lock;
189        if (old & _DRM_LOCK_HELD)
190            new = old | _DRM_LOCK_CONT;
191        else {
192            new = context | _DRM_LOCK_HELD |
193                ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ?
194                 _DRM_LOCK_CONT : 0);
195        }
196        prev = cmpxchg(lock, old, new);
197    } while (prev != old);
198    spin_unlock_bh(&lock_data->spinlock);
199
200    if (_DRM_LOCKING_CONTEXT(old) == context) {
201        if (old & _DRM_LOCK_HELD) {
202            if (context != DRM_KERNEL_CONTEXT) {
203                DRM_ERROR("%d holds heavyweight lock\n",
204                      context);
205            }
206            return 0;
207        }
208    }
209
210    if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) {
211        /* Have lock */
212        return 1;
213    }
214    return 0;
215}
216
217/**
218 * This takes a lock forcibly and hands it to context. Should ONLY be used
219 * inside *_unlock to give lock to kernel before calling *_dma_schedule.
220 *
221 * \param dev DRM device.
222 * \param lock lock pointer.
223 * \param context locking context.
224 * \return always one.
225 *
226 * Resets the lock file pointer.
227 * Marks the lock as held by the given context, via the \p cmpxchg instruction.
228 */
229static int drm_lock_transfer(struct drm_lock_data *lock_data,
230                 unsigned int context)
231{
232    unsigned int old, new, prev;
233    volatile unsigned int *lock = &lock_data->hw_lock->lock;
234
235    lock_data->file_priv = NULL;
236    do {
237        old = *lock;
238        new = context | _DRM_LOCK_HELD;
239        prev = cmpxchg(lock, old, new);
240    } while (prev != old);
241    return 1;
242}
243
244/**
245 * Free lock.
246 *
247 * \param dev DRM device.
248 * \param lock lock.
249 * \param context context.
250 *
251 * Resets the lock file pointer.
252 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task
253 * waiting on the lock queue.
254 */
255int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context)
256{
257    unsigned int old, new, prev;
258    volatile unsigned int *lock = &lock_data->hw_lock->lock;
259
260    spin_lock_bh(&lock_data->spinlock);
261    if (lock_data->kernel_waiters != 0) {
262        drm_lock_transfer(lock_data, 0);
263        lock_data->idle_has_lock = 1;
264        spin_unlock_bh(&lock_data->spinlock);
265        return 1;
266    }
267    spin_unlock_bh(&lock_data->spinlock);
268
269    do {
270        old = *lock;
271        new = _DRM_LOCKING_CONTEXT(old);
272        prev = cmpxchg(lock, old, new);
273    } while (prev != old);
274
275    if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) {
276        DRM_ERROR("%d freed heavyweight lock held by %d\n",
277              context, _DRM_LOCKING_CONTEXT(old));
278        return 1;
279    }
280    wake_up_interruptible(&lock_data->lock_queue);
281    return 0;
282}
283
284/**
285 * If we get here, it means that the process has called DRM_IOCTL_LOCK
286 * without calling DRM_IOCTL_UNLOCK.
287 *
288 * If the lock is not held, then let the signal proceed as usual. If the lock
289 * is held, then set the contended flag and keep the signal blocked.
290 *
291 * \param priv pointer to a drm_sigdata structure.
292 * \return one if the signal should be delivered normally, or zero if the
293 * signal should be blocked.
294 */
295static int drm_notifier(void *priv)
296{
297    struct drm_sigdata *s = (struct drm_sigdata *) priv;
298    unsigned int old, new, prev;
299
300    /* Allow signal delivery if lock isn't held */
301    if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock)
302        || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context)
303        return 1;
304
305    /* Otherwise, set flag to force call to
306       drmUnlock */
307    do {
308        old = s->lock->lock;
309        new = old | _DRM_LOCK_CONT;
310        prev = cmpxchg(&s->lock->lock, old, new);
311    } while (prev != old);
312    return 0;
313}
314
315/**
316 * This function returns immediately and takes the hw lock
317 * with the kernel context if it is free, otherwise it gets the highest priority when and if
318 * it is eventually released.
319 *
320 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held
321 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause
322 * a deadlock, which is why the "idlelock" was invented).
323 *
324 * This should be sufficient to wait for GPU idle without
325 * having to worry about starvation.
326 */
327
328void drm_idlelock_take(struct drm_lock_data *lock_data)
329{
330    int ret;
331
332    spin_lock_bh(&lock_data->spinlock);
333    lock_data->kernel_waiters++;
334    if (!lock_data->idle_has_lock) {
335
336        spin_unlock_bh(&lock_data->spinlock);
337        ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT);
338        spin_lock_bh(&lock_data->spinlock);
339
340        if (ret == 1)
341            lock_data->idle_has_lock = 1;
342    }
343    spin_unlock_bh(&lock_data->spinlock);
344}
345EXPORT_SYMBOL(drm_idlelock_take);
346
347void drm_idlelock_release(struct drm_lock_data *lock_data)
348{
349    unsigned int old, prev;
350    volatile unsigned int *lock = &lock_data->hw_lock->lock;
351
352    spin_lock_bh(&lock_data->spinlock);
353    if (--lock_data->kernel_waiters == 0) {
354        if (lock_data->idle_has_lock) {
355            do {
356                old = *lock;
357                prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT);
358            } while (prev != old);
359            wake_up_interruptible(&lock_data->lock_queue);
360            lock_data->idle_has_lock = 0;
361        }
362    }
363    spin_unlock_bh(&lock_data->spinlock);
364}
365EXPORT_SYMBOL(drm_idlelock_release);
366
367int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv)
368{
369    struct drm_master *master = file_priv->master;
370    return (file_priv->lock_count && master->lock.hw_lock &&
371        _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) &&
372        master->lock.file_priv == file_priv);
373}
374

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