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