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