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 <drm/drmP.h> 38 #include "drm_legacy.h" 39 40 static int drm_notifier(void *priv); 41 42 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context); 43 44 /** 45 * Lock ioctl. 46 * 47 * \param inode device inode. 48 * \param file_priv DRM file private. 49 * \param cmd command. 50 * \param arg user argument, pointing to a drm_lock structure. 51 * \return zero on success or negative number on failure. 52 * 53 * Add the current task to the lock wait queue, and attempt to take to lock. 54 */ 55 int drm_lock(struct drm_device *dev, void *data, struct drm_file *file_priv) 56 { 57 DECLARE_WAITQUEUE(entry, current); 58 struct drm_lock *lock = data; 59 struct drm_master *master = file_priv->master; 60 int ret = 0; 61 62 ++file_priv->lock_count; 63 64 if (lock->context == DRM_KERNEL_CONTEXT) { 65 DRM_ERROR("Process %d using kernel context %d\n", 66 task_pid_nr(current), lock->context); 67 return -EINVAL; 68 } 69 70 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 71 lock->context, task_pid_nr(current), 72 master->lock.hw_lock->lock, lock->flags); 73 74 add_wait_queue(&master->lock.lock_queue, &entry); 75 spin_lock_bh(&master->lock.spinlock); 76 master->lock.user_waiters++; 77 spin_unlock_bh(&master->lock.spinlock); 78 79 for (;;) { 80 __set_current_state(TASK_INTERRUPTIBLE); 81 if (!master->lock.hw_lock) { 82 /* Device has been unregistered */ 83 send_sig(SIGTERM, current, 0); 84 ret = -EINTR; 85 break; 86 } 87 if (drm_lock_take(&master->lock, lock->context)) { 88 master->lock.file_priv = file_priv; 89 master->lock.lock_time = jiffies; 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 */ 149 int 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 if (drm_lock_free(&master->lock, lock->context)) { 161 /* FIXME: Should really bail out here. */ 162 } 163 164 unblock_all_signals(); 165 return 0; 166 } 167 168 /** 169 * Take the heavyweight lock. 170 * 171 * \param lock lock pointer. 172 * \param context locking context. 173 * \return one if the lock is held, or zero otherwise. 174 * 175 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction. 176 */ 177 static 178 int drm_lock_take(struct drm_lock_data *lock_data, 179 unsigned int context) 180 { 181 unsigned int old, new, prev; 182 volatile unsigned int *lock = &lock_data->hw_lock->lock; 183 184 spin_lock_bh(&lock_data->spinlock); 185 do { 186 old = *lock; 187 if (old & _DRM_LOCK_HELD) 188 new = old | _DRM_LOCK_CONT; 189 else { 190 new = context | _DRM_LOCK_HELD | 191 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ? 192 _DRM_LOCK_CONT : 0); 193 } 194 prev = cmpxchg(lock, old, new); 195 } while (prev != old); 196 spin_unlock_bh(&lock_data->spinlock); 197 198 if (_DRM_LOCKING_CONTEXT(old) == context) { 199 if (old & _DRM_LOCK_HELD) { 200 if (context != DRM_KERNEL_CONTEXT) { 201 DRM_ERROR("%d holds heavyweight lock\n", 202 context); 203 } 204 return 0; 205 } 206 } 207 208 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) { 209 /* Have lock */ 210 return 1; 211 } 212 return 0; 213 } 214 215 /** 216 * This takes a lock forcibly and hands it to context. Should ONLY be used 217 * inside *_unlock to give lock to kernel before calling *_dma_schedule. 218 * 219 * \param dev DRM device. 220 * \param lock lock pointer. 221 * \param context locking context. 222 * \return always one. 223 * 224 * Resets the lock file pointer. 225 * Marks the lock as held by the given context, via the \p cmpxchg instruction. 226 */ 227 static int drm_lock_transfer(struct drm_lock_data *lock_data, 228 unsigned int context) 229 { 230 unsigned int old, new, prev; 231 volatile unsigned int *lock = &lock_data->hw_lock->lock; 232 233 lock_data->file_priv = NULL; 234 do { 235 old = *lock; 236 new = context | _DRM_LOCK_HELD; 237 prev = cmpxchg(lock, old, new); 238 } while (prev != old); 239 return 1; 240 } 241 242 /** 243 * Free lock. 244 * 245 * \param dev DRM device. 246 * \param lock lock. 247 * \param context context. 248 * 249 * Resets the lock file pointer. 250 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task 251 * waiting on the lock queue. 252 */ 253 int drm_lock_free(struct drm_lock_data *lock_data, unsigned int context) 254 { 255 unsigned int old, new, prev; 256 volatile unsigned int *lock = &lock_data->hw_lock->lock; 257 258 spin_lock_bh(&lock_data->spinlock); 259 if (lock_data->kernel_waiters != 0) { 260 drm_lock_transfer(lock_data, 0); 261 lock_data->idle_has_lock = 1; 262 spin_unlock_bh(&lock_data->spinlock); 263 return 1; 264 } 265 spin_unlock_bh(&lock_data->spinlock); 266 267 do { 268 old = *lock; 269 new = _DRM_LOCKING_CONTEXT(old); 270 prev = cmpxchg(lock, old, new); 271 } while (prev != old); 272 273 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 274 DRM_ERROR("%d freed heavyweight lock held by %d\n", 275 context, _DRM_LOCKING_CONTEXT(old)); 276 return 1; 277 } 278 wake_up_interruptible(&lock_data->lock_queue); 279 return 0; 280 } 281 282 /** 283 * If we get here, it means that the process has called DRM_IOCTL_LOCK 284 * without calling DRM_IOCTL_UNLOCK. 285 * 286 * If the lock is not held, then let the signal proceed as usual. If the lock 287 * is held, then set the contended flag and keep the signal blocked. 288 * 289 * \param priv pointer to a drm_sigdata structure. 290 * \return one if the signal should be delivered normally, or zero if the 291 * signal should be blocked. 292 */ 293 static int drm_notifier(void *priv) 294 { 295 struct drm_sigdata *s = (struct drm_sigdata *) priv; 296 unsigned int old, new, prev; 297 298 /* Allow signal delivery if lock isn't held */ 299 if (!s->lock || !_DRM_LOCK_IS_HELD(s->lock->lock) 300 || _DRM_LOCKING_CONTEXT(s->lock->lock) != s->context) 301 return 1; 302 303 /* Otherwise, set flag to force call to 304 drmUnlock */ 305 do { 306 old = s->lock->lock; 307 new = old | _DRM_LOCK_CONT; 308 prev = cmpxchg(&s->lock->lock, old, new); 309 } while (prev != old); 310 return 0; 311 } 312 313 /** 314 * This function returns immediately and takes the hw lock 315 * with the kernel context if it is free, otherwise it gets the highest priority when and if 316 * it is eventually released. 317 * 318 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held 319 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause 320 * a deadlock, which is why the "idlelock" was invented). 321 * 322 * This should be sufficient to wait for GPU idle without 323 * having to worry about starvation. 324 */ 325 326 void drm_idlelock_take(struct drm_lock_data *lock_data) 327 { 328 int ret; 329 330 spin_lock_bh(&lock_data->spinlock); 331 lock_data->kernel_waiters++; 332 if (!lock_data->idle_has_lock) { 333 334 spin_unlock_bh(&lock_data->spinlock); 335 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT); 336 spin_lock_bh(&lock_data->spinlock); 337 338 if (ret == 1) 339 lock_data->idle_has_lock = 1; 340 } 341 spin_unlock_bh(&lock_data->spinlock); 342 } 343 EXPORT_SYMBOL(drm_idlelock_take); 344 345 void drm_idlelock_release(struct drm_lock_data *lock_data) 346 { 347 unsigned int old, prev; 348 volatile unsigned int *lock = &lock_data->hw_lock->lock; 349 350 spin_lock_bh(&lock_data->spinlock); 351 if (--lock_data->kernel_waiters == 0) { 352 if (lock_data->idle_has_lock) { 353 do { 354 old = *lock; 355 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT); 356 } while (prev != old); 357 wake_up_interruptible(&lock_data->lock_queue); 358 lock_data->idle_has_lock = 0; 359 } 360 } 361 spin_unlock_bh(&lock_data->spinlock); 362 } 363 EXPORT_SYMBOL(drm_idlelock_release); 364 365 int drm_i_have_hw_lock(struct drm_device *dev, struct drm_file *file_priv) 366 { 367 struct drm_master *master = file_priv->master; 368 return (file_priv->lock_count && master->lock.hw_lock && 369 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) && 370 master->lock.file_priv == file_priv); 371 } 372