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 <linux/sched/signal.h> 38 39 #include <drm/drm.h> 40 #include <drm/drm_drv.h> 41 #include <drm/drm_file.h> 42 #include <drm/drm_print.h> 43 44 #include "drm_internal.h" 45 #include "drm_legacy.h" 46 47 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context); 48 49 /** 50 * Take the heavyweight lock. 51 * 52 * \param lock lock pointer. 53 * \param context locking context. 54 * \return one if the lock is held, or zero otherwise. 55 * 56 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction. 57 */ 58 static 59 int drm_lock_take(struct drm_lock_data *lock_data, 60 unsigned int context) 61 { 62 unsigned int old, new, prev; 63 volatile unsigned int *lock = &lock_data->hw_lock->lock; 64 65 spin_lock_bh(&lock_data->spinlock); 66 do { 67 old = *lock; 68 if (old & _DRM_LOCK_HELD) 69 new = old | _DRM_LOCK_CONT; 70 else { 71 new = context | _DRM_LOCK_HELD | 72 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ? 73 _DRM_LOCK_CONT : 0); 74 } 75 prev = cmpxchg(lock, old, new); 76 } while (prev != old); 77 spin_unlock_bh(&lock_data->spinlock); 78 79 if (_DRM_LOCKING_CONTEXT(old) == context) { 80 if (old & _DRM_LOCK_HELD) { 81 if (context != DRM_KERNEL_CONTEXT) { 82 DRM_ERROR("%d holds heavyweight lock\n", 83 context); 84 } 85 return 0; 86 } 87 } 88 89 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) { 90 /* Have lock */ 91 return 1; 92 } 93 return 0; 94 } 95 96 /** 97 * This takes a lock forcibly and hands it to context. Should ONLY be used 98 * inside *_unlock to give lock to kernel before calling *_dma_schedule. 99 * 100 * \param dev DRM device. 101 * \param lock lock pointer. 102 * \param context locking context. 103 * \return always one. 104 * 105 * Resets the lock file pointer. 106 * Marks the lock as held by the given context, via the \p cmpxchg instruction. 107 */ 108 static int drm_lock_transfer(struct drm_lock_data *lock_data, 109 unsigned int context) 110 { 111 unsigned int old, new, prev; 112 volatile unsigned int *lock = &lock_data->hw_lock->lock; 113 114 lock_data->file_priv = NULL; 115 do { 116 old = *lock; 117 new = context | _DRM_LOCK_HELD; 118 prev = cmpxchg(lock, old, new); 119 } while (prev != old); 120 return 1; 121 } 122 123 static int drm_legacy_lock_free(struct drm_lock_data *lock_data, 124 unsigned int context) 125 { 126 unsigned int old, new, prev; 127 volatile unsigned int *lock = &lock_data->hw_lock->lock; 128 129 spin_lock_bh(&lock_data->spinlock); 130 if (lock_data->kernel_waiters != 0) { 131 drm_lock_transfer(lock_data, 0); 132 lock_data->idle_has_lock = 1; 133 spin_unlock_bh(&lock_data->spinlock); 134 return 1; 135 } 136 spin_unlock_bh(&lock_data->spinlock); 137 138 do { 139 old = *lock; 140 new = _DRM_LOCKING_CONTEXT(old); 141 prev = cmpxchg(lock, old, new); 142 } while (prev != old); 143 144 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 145 DRM_ERROR("%d freed heavyweight lock held by %d\n", 146 context, _DRM_LOCKING_CONTEXT(old)); 147 return 1; 148 } 149 wake_up_interruptible(&lock_data->lock_queue); 150 return 0; 151 } 152 153 /** 154 * Lock ioctl. 155 * 156 * \param inode device inode. 157 * \param file_priv DRM file private. 158 * \param cmd command. 159 * \param arg user argument, pointing to a drm_lock structure. 160 * \return zero on success or negative number on failure. 161 * 162 * Add the current task to the lock wait queue, and attempt to take to lock. 163 */ 164 int drm_legacy_lock(struct drm_device *dev, void *data, 165 struct drm_file *file_priv) 166 { 167 DECLARE_WAITQUEUE(entry, current); 168 struct drm_lock *lock = data; 169 struct drm_master *master = file_priv->master; 170 int ret = 0; 171 172 if (!drm_core_check_feature(dev, DRIVER_LEGACY)) 173 return -EOPNOTSUPP; 174 175 ++file_priv->lock_count; 176 177 if (lock->context == DRM_KERNEL_CONTEXT) { 178 DRM_ERROR("Process %d using kernel context %d\n", 179 task_pid_nr(current), lock->context); 180 return -EINVAL; 181 } 182 183 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 184 lock->context, task_pid_nr(current), 185 master->lock.hw_lock ? master->lock.hw_lock->lock : -1, 186 lock->flags); 187 188 add_wait_queue(&master->lock.lock_queue, &entry); 189 spin_lock_bh(&master->lock.spinlock); 190 master->lock.user_waiters++; 191 spin_unlock_bh(&master->lock.spinlock); 192 193 for (;;) { 194 __set_current_state(TASK_INTERRUPTIBLE); 195 if (!master->lock.hw_lock) { 196 /* Device has been unregistered */ 197 send_sig(SIGTERM, current, 0); 198 ret = -EINTR; 199 break; 200 } 201 if (drm_lock_take(&master->lock, lock->context)) { 202 master->lock.file_priv = file_priv; 203 master->lock.lock_time = jiffies; 204 break; /* Got lock */ 205 } 206 207 /* Contention */ 208 mutex_unlock(&drm_global_mutex); 209 schedule(); 210 mutex_lock(&drm_global_mutex); 211 if (signal_pending(current)) { 212 ret = -EINTR; 213 break; 214 } 215 } 216 spin_lock_bh(&master->lock.spinlock); 217 master->lock.user_waiters--; 218 spin_unlock_bh(&master->lock.spinlock); 219 __set_current_state(TASK_RUNNING); 220 remove_wait_queue(&master->lock.lock_queue, &entry); 221 222 DRM_DEBUG("%d %s\n", lock->context, 223 ret ? "interrupted" : "has lock"); 224 if (ret) return ret; 225 226 /* don't set the block all signals on the master process for now 227 * really probably not the correct answer but lets us debug xkb 228 * xserver for now */ 229 if (!drm_is_current_master(file_priv)) { 230 dev->sigdata.context = lock->context; 231 dev->sigdata.lock = master->lock.hw_lock; 232 } 233 234 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT)) 235 { 236 if (dev->driver->dma_quiescent(dev)) { 237 DRM_DEBUG("%d waiting for DMA quiescent\n", 238 lock->context); 239 return -EBUSY; 240 } 241 } 242 243 return 0; 244 } 245 246 /** 247 * Unlock ioctl. 248 * 249 * \param inode device inode. 250 * \param file_priv DRM file private. 251 * \param cmd command. 252 * \param arg user argument, pointing to a drm_lock structure. 253 * \return zero on success or negative number on failure. 254 * 255 * Transfer and free the lock. 256 */ 257 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) 258 { 259 struct drm_lock *lock = data; 260 struct drm_master *master = file_priv->master; 261 262 if (!drm_core_check_feature(dev, DRIVER_LEGACY)) 263 return -EOPNOTSUPP; 264 265 if (lock->context == DRM_KERNEL_CONTEXT) { 266 DRM_ERROR("Process %d using kernel context %d\n", 267 task_pid_nr(current), lock->context); 268 return -EINVAL; 269 } 270 271 if (drm_legacy_lock_free(&master->lock, lock->context)) { 272 /* FIXME: Should really bail out here. */ 273 } 274 275 return 0; 276 } 277 278 /** 279 * This function returns immediately and takes the hw lock 280 * with the kernel context if it is free, otherwise it gets the highest priority when and if 281 * it is eventually released. 282 * 283 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held 284 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause 285 * a deadlock, which is why the "idlelock" was invented). 286 * 287 * This should be sufficient to wait for GPU idle without 288 * having to worry about starvation. 289 */ 290 291 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data) 292 { 293 int ret; 294 295 spin_lock_bh(&lock_data->spinlock); 296 lock_data->kernel_waiters++; 297 if (!lock_data->idle_has_lock) { 298 299 spin_unlock_bh(&lock_data->spinlock); 300 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT); 301 spin_lock_bh(&lock_data->spinlock); 302 303 if (ret == 1) 304 lock_data->idle_has_lock = 1; 305 } 306 spin_unlock_bh(&lock_data->spinlock); 307 } 308 EXPORT_SYMBOL(drm_legacy_idlelock_take); 309 310 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data) 311 { 312 unsigned int old, prev; 313 volatile unsigned int *lock = &lock_data->hw_lock->lock; 314 315 spin_lock_bh(&lock_data->spinlock); 316 if (--lock_data->kernel_waiters == 0) { 317 if (lock_data->idle_has_lock) { 318 do { 319 old = *lock; 320 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT); 321 } while (prev != old); 322 wake_up_interruptible(&lock_data->lock_queue); 323 lock_data->idle_has_lock = 0; 324 } 325 } 326 spin_unlock_bh(&lock_data->spinlock); 327 } 328 EXPORT_SYMBOL(drm_legacy_idlelock_release); 329 330 static int drm_legacy_i_have_hw_lock(struct drm_device *dev, 331 struct drm_file *file_priv) 332 { 333 struct drm_master *master = file_priv->master; 334 return (file_priv->lock_count && master->lock.hw_lock && 335 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) && 336 master->lock.file_priv == file_priv); 337 } 338 339 void drm_legacy_lock_release(struct drm_device *dev, struct file *filp) 340 { 341 struct drm_file *file_priv = filp->private_data; 342 343 /* if the master has gone away we can't do anything with the lock */ 344 if (!dev->master) 345 return; 346 347 if (drm_legacy_i_have_hw_lock(dev, file_priv)) { 348 DRM_DEBUG("File %p released, freeing lock for context %d\n", 349 filp, _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock)); 350 drm_legacy_lock_free(&file_priv->master->lock, 351 _DRM_LOCKING_CONTEXT(file_priv->master->lock.hw_lock->lock)); 352 } 353 } 354 355 void drm_legacy_lock_master_cleanup(struct drm_device *dev, struct drm_master *master) 356 { 357 if (!drm_core_check_feature(dev, DRIVER_LEGACY)) 358 return; 359 360 /* 361 * Since the master is disappearing, so is the 362 * possibility to lock. 363 */ mutex_lock(&dev->struct_mutex); 364 if (master->lock.hw_lock) { 365 if (dev->sigdata.lock == master->lock.hw_lock) 366 dev->sigdata.lock = NULL; 367 master->lock.hw_lock = NULL; 368 master->lock.file_priv = NULL; 369 wake_up_interruptible_all(&master->lock.lock_queue); 370 } 371 mutex_unlock(&dev->struct_mutex); 372 } 373