1 /* $NetBSD: drm_lock.c,v 1.3 2021/12/18 23:44:57 riastradh Exp $ */ 2 3 /* 4 * \file drm_lock.c 5 * IOCTLs for locking 6 * 7 * \author Rickard E. (Rik) Faith <faith@valinux.com> 8 * \author Gareth Hughes <gareth@valinux.com> 9 */ 10 11 /* 12 * Created: Tue Feb 2 08:37:54 1999 by faith@valinux.com 13 * 14 * Copyright 1999 Precision Insight, Inc., Cedar Park, Texas. 15 * Copyright 2000 VA Linux Systems, Inc., Sunnyvale, California. 16 * All Rights Reserved. 17 * 18 * Permission is hereby granted, free of charge, to any person obtaining a 19 * copy of this software and associated documentation files (the "Software"), 20 * to deal in the Software without restriction, including without limitation 21 * the rights to use, copy, modify, merge, publish, distribute, sublicense, 22 * and/or sell copies of the Software, and to permit persons to whom the 23 * Software is furnished to do so, subject to the following conditions: 24 * 25 * The above copyright notice and this permission notice (including the next 26 * paragraph) shall be included in all copies or substantial portions of the 27 * Software. 28 * 29 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 30 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 31 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL 32 * VA LINUX SYSTEMS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR 33 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, 34 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR 35 * OTHER DEALINGS IN THE SOFTWARE. 36 */ 37 38 #include <sys/cdefs.h> 39 __KERNEL_RCSID(0, "$NetBSD: drm_lock.c,v 1.3 2021/12/18 23:44:57 riastradh Exp $"); 40 41 #include <linux/export.h> 42 #include <linux/sched/signal.h> 43 44 #include <drm/drm.h> 45 #include <drm/drm_drv.h> 46 #include <drm/drm_file.h> 47 #include <drm/drm_print.h> 48 49 #include "drm_internal.h" 50 #include "drm_legacy.h" 51 52 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context); 53 54 /** 55 * Take the heavyweight lock. 56 * 57 * \param lock lock pointer. 58 * \param context locking context. 59 * \return one if the lock is held, or zero otherwise. 60 * 61 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction. 62 */ 63 static 64 int drm_lock_take(struct drm_lock_data *lock_data, 65 unsigned int context) 66 { 67 unsigned int old, new, prev; 68 volatile unsigned int *lock = &lock_data->hw_lock->lock; 69 70 spin_lock_bh(&lock_data->spinlock); 71 do { 72 old = *lock; 73 if (old & _DRM_LOCK_HELD) 74 new = old | _DRM_LOCK_CONT; 75 else { 76 new = context | _DRM_LOCK_HELD | 77 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ? 78 _DRM_LOCK_CONT : 0); 79 } 80 prev = cmpxchg(lock, old, new); 81 } while (prev != old); 82 spin_unlock_bh(&lock_data->spinlock); 83 84 if (_DRM_LOCKING_CONTEXT(old) == context) { 85 if (old & _DRM_LOCK_HELD) { 86 if (context != DRM_KERNEL_CONTEXT) { 87 DRM_ERROR("%d holds heavyweight lock\n", 88 context); 89 } 90 return 0; 91 } 92 } 93 94 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) { 95 /* Have lock */ 96 return 1; 97 } 98 return 0; 99 } 100 101 /** 102 * This takes a lock forcibly and hands it to context. Should ONLY be used 103 * inside *_unlock to give lock to kernel before calling *_dma_schedule. 104 * 105 * \param dev DRM device. 106 * \param lock lock pointer. 107 * \param context locking context. 108 * \return always one. 109 * 110 * Resets the lock file pointer. 111 * Marks the lock as held by the given context, via the \p cmpxchg instruction. 112 */ 113 static int drm_lock_transfer(struct drm_lock_data *lock_data, 114 unsigned int context) 115 { 116 unsigned int old, new, prev; 117 volatile unsigned int *lock = &lock_data->hw_lock->lock; 118 119 lock_data->file_priv = NULL; 120 do { 121 old = *lock; 122 new = context | _DRM_LOCK_HELD; 123 prev = cmpxchg(lock, old, new); 124 } while (prev != old); 125 return 1; 126 } 127 128 static int drm_legacy_lock_free(struct drm_lock_data *lock_data, 129 unsigned int context) 130 { 131 unsigned int old, new, prev; 132 volatile unsigned int *lock = &lock_data->hw_lock->lock; 133 134 spin_lock_bh(&lock_data->spinlock); 135 if (lock_data->kernel_waiters != 0) { 136 drm_lock_transfer(lock_data, 0); 137 lock_data->idle_has_lock = 1; 138 spin_unlock_bh(&lock_data->spinlock); 139 return 1; 140 } 141 spin_unlock_bh(&lock_data->spinlock); 142 143 do { 144 old = *lock; 145 new = _DRM_LOCKING_CONTEXT(old); 146 prev = cmpxchg(lock, old, new); 147 } while (prev != old); 148 149 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 150 DRM_ERROR("%d freed heavyweight lock held by %d\n", 151 context, _DRM_LOCKING_CONTEXT(old)); 152 return 1; 153 } 154 wake_up_interruptible(&lock_data->lock_queue); 155 return 0; 156 } 157 158 /** 159 * Lock ioctl. 160 * 161 * \param inode device inode. 162 * \param file_priv DRM file private. 163 * \param cmd command. 164 * \param arg user argument, pointing to a drm_lock structure. 165 * \return zero on success or negative number on failure. 166 * 167 * Add the current task to the lock wait queue, and attempt to take to lock. 168 */ 169 int drm_legacy_lock(struct drm_device *dev, void *data, 170 struct drm_file *file_priv) 171 { 172 DECLARE_WAITQUEUE(entry, current); 173 struct drm_lock *lock = data; 174 struct drm_master *master = file_priv->master; 175 int ret = 0; 176 177 if (!drm_core_check_feature(dev, DRIVER_LEGACY)) 178 return -EOPNOTSUPP; 179 180 ++file_priv->lock_count; 181 182 if (lock->context == DRM_KERNEL_CONTEXT) { 183 DRM_ERROR("Process %d using kernel context %d\n", 184 task_pid_nr(current), lock->context); 185 return -EINVAL; 186 } 187 188 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 189 lock->context, task_pid_nr(current), 190 master->lock.hw_lock ? master->lock.hw_lock->lock : -1, 191 lock->flags); 192 193 add_wait_queue(&master->lock.lock_queue, &entry); 194 spin_lock_bh(&master->lock.spinlock); 195 master->lock.user_waiters++; 196 spin_unlock_bh(&master->lock.spinlock); 197 198 for (;;) { 199 __set_current_state(TASK_INTERRUPTIBLE); 200 if (!master->lock.hw_lock) { 201 /* Device has been unregistered */ 202 send_sig(SIGTERM, current, 0); 203 ret = -EINTR; 204 break; 205 } 206 if (drm_lock_take(&master->lock, lock->context)) { 207 master->lock.file_priv = file_priv; 208 master->lock.lock_time = jiffies; 209 break; /* Got lock */ 210 } 211 212 /* Contention */ 213 mutex_unlock(&drm_global_mutex); 214 schedule(); 215 mutex_lock(&drm_global_mutex); 216 if (signal_pending(current)) { 217 ret = -EINTR; 218 break; 219 } 220 } 221 spin_lock_bh(&master->lock.spinlock); 222 master->lock.user_waiters--; 223 spin_unlock_bh(&master->lock.spinlock); 224 __set_current_state(TASK_RUNNING); 225 remove_wait_queue(&master->lock.lock_queue, &entry); 226 227 DRM_DEBUG("%d %s\n", lock->context, 228 ret ? "interrupted" : "has lock"); 229 if (ret) return ret; 230 231 /* don't set the block all signals on the master process for now 232 * really probably not the correct answer but lets us debug xkb 233 * xserver for now */ 234 if (!drm_is_current_master(file_priv)) { 235 dev->sigdata.context = lock->context; 236 dev->sigdata.lock = master->lock.hw_lock; 237 } 238 239 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT)) 240 { 241 if (dev->driver->dma_quiescent(dev)) { 242 DRM_DEBUG("%d waiting for DMA quiescent\n", 243 lock->context); 244 return -EBUSY; 245 } 246 } 247 248 return 0; 249 } 250 251 /** 252 * Unlock ioctl. 253 * 254 * \param inode device inode. 255 * \param file_priv DRM file private. 256 * \param cmd command. 257 * \param arg user argument, pointing to a drm_lock structure. 258 * \return zero on success or negative number on failure. 259 * 260 * Transfer and free the lock. 261 */ 262 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) 263 { 264 struct drm_lock *lock = data; 265 struct drm_master *master = file_priv->master; 266 267 if (!drm_core_check_feature(dev, DRIVER_LEGACY)) 268 return -EOPNOTSUPP; 269 270 if (lock->context == DRM_KERNEL_CONTEXT) { 271 DRM_ERROR("Process %d using kernel context %d\n", 272 task_pid_nr(current), lock->context); 273 return -EINVAL; 274 } 275 276 if (drm_legacy_lock_free(&master->lock, lock->context)) { 277 /* FIXME: Should really bail out here. */ 278 } 279 280 return 0; 281 } 282 283 /** 284 * This function returns immediately and takes the hw lock 285 * with the kernel context if it is free, otherwise it gets the highest priority when and if 286 * it is eventually released. 287 * 288 * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held 289 * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause 290 * a deadlock, which is why the "idlelock" was invented). 291 * 292 * This should be sufficient to wait for GPU idle without 293 * having to worry about starvation. 294 */ 295 296 void drm_legacy_idlelock_take(struct drm_lock_data *lock_data) 297 { 298 int ret; 299 300 spin_lock_bh(&lock_data->spinlock); 301 lock_data->kernel_waiters++; 302 if (!lock_data->idle_has_lock) { 303 304 spin_unlock_bh(&lock_data->spinlock); 305 ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT); 306 spin_lock_bh(&lock_data->spinlock); 307 308 if (ret == 1) 309 lock_data->idle_has_lock = 1; 310 } 311 spin_unlock_bh(&lock_data->spinlock); 312 } 313 EXPORT_SYMBOL(drm_legacy_idlelock_take); 314 315 void drm_legacy_idlelock_release(struct drm_lock_data *lock_data) 316 { 317 unsigned int old, prev; 318 volatile unsigned int *lock = &lock_data->hw_lock->lock; 319 320 spin_lock_bh(&lock_data->spinlock); 321 if (--lock_data->kernel_waiters == 0) { 322 if (lock_data->idle_has_lock) { 323 do { 324 old = *lock; 325 prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT); 326 } while (prev != old); 327 wake_up_interruptible(&lock_data->lock_queue); 328 lock_data->idle_has_lock = 0; 329 } 330 } 331 spin_unlock_bh(&lock_data->spinlock); 332 } 333 EXPORT_SYMBOL(drm_legacy_idlelock_release); 334 335 static int drm_legacy_i_have_hw_lock(struct drm_device *dev, 336 struct drm_file *file_priv) 337 { 338 struct drm_master *master = file_priv->master; 339 return (file_priv->lock_count && master->lock.hw_lock && 340 _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) && 341 master->lock.file_priv == file_priv); 342 } 343 344 void drm_legacy_lock_release(struct drm_device *dev, struct file *filp) 345 { 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 } 359 360 void drm_legacy_lock_master_cleanup(struct drm_device *dev, struct drm_master *master) 361 { 362 if (!drm_core_check_feature(dev, DRIVER_LEGACY)) 363 return; 364 365 /* 366 * Since the master is disappearing, so is the 367 * possibility to lock. 368 */ 369 mutex_lock(&dev->struct_mutex); 370 if (master->lock.hw_lock) { 371 if (dev->sigdata.lock == master->lock.hw_lock) 372 dev->sigdata.lock = NULL; 373 master->lock.hw_lock = NULL; 374 master->lock.file_priv = NULL; 375 wake_up_interruptible_all(&master->lock.lock_queue); 376 } 377 mutex_unlock(&dev->struct_mutex); 378 } 379