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_notifier(void *priv); 39 40 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context); 41 42 /** 43 * Lock ioctl. 44 * 45 * \param inode device inode. 46 * \param file_priv DRM file private. 47 * \param cmd command. 48 * \param arg user argument, pointing to a drm_lock structure. 49 * \return zero on success or negative number on failure. 50 * 51 * Add the current task to the lock wait queue, and attempt to take to lock. 52 */ 53 int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv) 54 { 55 DECLARE_WAITQUEUE(entry, current); 56 struct drm_lock *lock = data; 57 struct drm_master *master = file_priv->master; 58 int ret = 0; 59 60 ++file_priv->lock_count; 61 62 if (lock->context == DRM_KERNEL_CONTEXT) { 63 DRM_ERROR("Process %d using kernel context %d\n", 64 task_pid_nr(current), lock->context); 65 return -EINVAL; 66 } 67 68 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 69 lock->context, task_pid_nr(current), 70 master->lock.hw_lock->lock, lock->flags); 71 72 if (drm_core_check_feature(dev, DRIVER_DMA_QUEUE)) 73 if (lock->context < 0) 74 return -EINVAL; 75 76 add_wait_queue(&master->lock.lock_queue, &entry); 77 spin_lock_bh(&master->lock.spinlock); 78 master->lock.user_waiters++; 79 spin_unlock_bh(&master->lock.spinlock); 80 81 for (;;) { 82 __set_current_state(TASK_INTERRUPTIBLE); 83 if (!master->lock.hw_lock) { 84 /* Device has been unregistered */ 85 send_sig(SIGTERM, current, 0); 86 ret = -EINTR; 87 break; 88 } 89 if (drm_lock_take(&master->lock, lock->context)) { 90 master->lock.file_priv = file_priv; 91 master->lock.lock_time = jiffies; 92 atomic_inc(&dev->counts[_DRM_STAT_LOCKS]); 93 break; /* Got lock */ 94 } 95 96 /* Contention */ 97 mutex_unlock(&drm_global_mutex); 98 schedule(); 99 mutex_lock(&drm_global_mutex); 100 if (signal_pending(current)) { 101 ret = -EINTR; 102 break; 103 } 104 } 105 spin_lock_bh(&master->lock.spinlock); 106 master->lock.user_waiters--; 107 spin_unlock_bh(&master->lock.spinlock); 108 __set_current_state(TASK_RUNNING); 109 remove_wait_queue(&master->lock.lock_queue, &entry); 110 111 DRM_DEBUG("%d %s\n", lock->context, 112 ret ? "interrupted" : "has lock"); 113 if (ret) return ret; 114 115 /* don't set the block all signals on the master process for now 116 * really probably not the correct answer but lets us debug xkb 117 * xserver for now */ 118 if (!file_priv->is_master) { 119 sigemptyset(&dev->sigmask); 120 sigaddset(&dev->sigmask, SIGSTOP); 121 sigaddset(&dev->sigmask, SIGTSTP); 122 sigaddset(&dev->sigmask, SIGTTIN); 123 sigaddset(&dev->sigmask, SIGTTOU); 124 dev->sigdata.context = lock->context; 125 dev->sigdata.lock = master->lock.hw_lock; 126 block_all_signals(drm_notifier, &dev->sigdata, &dev->sigmask); 127 } 128 129 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT)) 130 { 131 if (dev->driver->dma_quiescent(dev)) { 132 DRM_DEBUG("%d waiting for DMA quiescent\n", 133 lock->context); 134 return -EBUSY; 135 } 136 } 137 138 return 0; 139 } 140 141 /** 142 * Unlock ioctl. 143 * 144 * \param inode device inode. 145 * \param file_priv DRM file private. 146 * \param cmd command. 147 * \param arg user argument, pointing to a drm_lock structure. 148 * \return zero on success or negative number on failure. 149 * 150 * Transfer and free the lock. 151 */ 152 int drm_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) 153 { 154 struct drm_lock *lock = data; 155 struct drm_master *master = file_priv->master; 156 157 if (lock->context == DRM_KERNEL_CONTEXT) { 158 DRM_ERROR("Process %d using kernel context %d\n", 159 task_pid_nr(current), lock->context); 160 return -EINVAL; 161 } 162 163 atomic_inc(&dev->counts[_DRM_STAT_UNLOCKS]); 164 165 if (drm_lock_free(&master->lock, lock->context)) { 166 /* FIXME: Should really bail out here. */ 167 } 168 169 unblock_all_signals(); 170 return 0; 171 } 172 173 /** 174 * Take the heavyweight lock. 175 * 176 * \param lock lock pointer. 177 * \param context locking context. 178 * \return one if the lock is held, or zero otherwise. 179 * 180 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction. 181 */ 182 static 183 int drm_lock_take(struct drm_lock_data *lock_data, 184 unsigned int context) 185 { 186 unsigned int old, new, prev; 187 volatile unsigned int *lock = &lock_data->hw_lock->lock; 188 189 spin_lock_bh(&lock_data->spinlock); 190 do { 191 old = *lock; 192 if (old & _DRM_LOCK_HELD) 193 new = old | _DRM_LOCK_CONT; 194 else { 195 new = context | _DRM_LOCK_HELD | 196 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ? 197 _DRM_LOCK_CONT : 0); 198 } 199 prev = cmpxchg(lock, old, new); 200 } while (prev != old); 201 spin_unlock_bh(&lock_data->spinlock); 202 203 if (_DRM_LOCKING_CONTEXT(old) == context) { 204 if (old & _DRM_LOCK_HELD) { 205 if (context != DRM_KERNEL_CONTEXT) { 206 DRM_ERROR("%d holds heavyweight lock\n", 207 context); 208 } 209 return 0; 210 } 211 } 212 213 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) { 214 /* Have lock */ 215 return 1; 216 } 217 return 0; 218 } 219 220 /** 221 * This takes a lock forcibly and hands it to context. Should ONLY be used 222 * inside *_unlock to give lock to kernel before calling *_dma_schedule. 223 * 224 * \param dev DRM device. 225 * \param lock lock pointer. 226 * \param context locking context. 227 * \return always one. 228 * 229 * Resets the lock file pointer. 230 * Marks the lock as held by the given context, via the \p cmpxchg instruction. 231 */ 232 static int drm_lock_transfer(struct drm_lock_data *lock_data, 233 unsigned int context) 234 { 235 unsigned int old, new, prev; 236 volatile unsigned int *lock = &lock_data->hw_lock->lock; 237 238 lock_data->file_priv = NULL; 239 do { 240 old = *lock; 241 new = context | _DRM_LOCK_HELD; 242 prev = cmpxchg(lock, old, new); 243 } while (prev != old); 244 return 1; 245 } 246 247 /** 248 * Free lock. 249 * 250 * \param dev DRM device. 251 * \param lock lock. 252 * \param context context. 253 * 254 * Resets the lock file pointer. 255 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task 256 * waiting on the lock queue. 257 */ 258 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context) 259 { 260 unsigned int old, new, prev; 261 volatile unsigned int *lock = &lock_data->hw_lock->lock; 262 263 spin_lock_bh(&lock_data->spinlock); 264 if (lock_data->kernel_waiters != 0) { 265 drm_lock_transfer(lock_data, 0); 266 lock_data->idle_has_lock = 1; 267 spin_unlock_bh(&lock_data->spinlock); 268 return 1; 269 } 270 spin_unlock_bh(&lock_data->spinlock); 271 272 do { 273 old = *lock; 274 new = _DRM_LOCKING_CONTEXT(old); 275 prev = cmpxchg(lock, old, new); 276 } while (prev != old); 277 278 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 279 DRM_ERROR("%d freed heavyweight lock held by %d\n", 280 context, _DRM_LOCKING_CONTEXT(old)); 281 return 1; 282 } 283 wake_up_interruptible(&lock_data->lock_queue); 284 return 0; 285 } 286 287 /** 288 * If we get here, it means that the process has called DRM_IOCTL_LOCK 289 * without calling DRM_IOCTL_UNLOCK. 290 * 291 * If the lock is not held, then let the signal proceed as usual. If the lock 292 * is held, then set the contended flag and keep the signal blocked. 293 * 294 * \param priv pointer to a drm_sigdata structure. 295 * \return one if the signal should be delivered normally, or zero if the 296 * signal should be blocked. 297 */ 298 static int drm_notifier(void *priv) 299 { 300 struct drm_sigdata *s = (struct drm_sigdata *) priv; 301 unsigned int old, new, prev; 302 303 /* Allow signal delivery if lock isn't held */ 304 if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock) 305 || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context) 306 return 1; 307 308 /* Otherwise, set flag to force call to 309 drmUnlock */ 310 do { 311 old = s->lock->lock; 312 new = old | _DRM_LOCK_CONT; 313 prev = cmpxchg(&s->lock->lock, old, new); 314 } while (prev != old); 315 return 0; 316 } 317 318 /** 319 * This function returns immediately and takes the hw lock 320 * with the kernel context if it is free, otherwise it gets the highest priority when and if 321 * it is eventually released. 322 * 323 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held 324 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause 325 * a deadlock, which is why the "idlelock" was invented). 326 * 327 * This should be sufficient to wait for GPU idle without 328 * having to worry about starvation. 329 */ 330 331 void drm_idlelock_take(struct drm_lock_data *lock_data) 332 { 333 int ret = 0; 334 335 spin_lock_bh(&lock_data->spinlock); 336 lock_data->kernel_waiters++; 337 if (!lock_data->idle_has_lock) { 338 339 spin_unlock_bh(&lock_data->spinlock); 340 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT); 341 spin_lock_bh(&lock_data->spinlock); 342 343 if (ret == 1) 344 lock_data->idle_has_lock = 1; 345 } 346 spin_unlock_bh(&lock_data->spinlock); 347 } 348 349 void drm_idlelock_release(struct drm_lock_data *lock_data) 350 { 351 unsigned int old, prev; 352 volatile unsigned int *lock = &lock_data->hw_lock->lock; 353 354 spin_lock_bh(&lock_data->spinlock); 355 if (--lock_data->kernel_waiters == 0) { 356 if (lock_data->idle_has_lock) { 357 do { 358 old = *lock; 359 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT); 360 } while (prev != old); 361 wake_up_interruptible(&lock_data->lock_queue); 362 lock_data->idle_has_lock = 0; 363 } 364 } 365 spin_unlock_bh(&lock_data->spinlock); 366 } 367 368 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv) 369 { 370 struct drm_master *master = file_priv->master; 371 return (file_priv->lock_count && master->lock.hw_lock && 372 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) && 373 master->lock.file_priv == file_priv); 374 } 375