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 #include "drm_internal.h" 40 41 static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context); 42 43 /** 44 * Lock ioctl. 45 * 46 * \param inode device inode. 47 * \param file_priv DRM file private. 48 * \param cmd command. 49 * \param arg user argument, pointing to a drm_lock structure. 50 * \return zero on success or negative number on failure. 51 * 52 * Add the current task to the lock wait queue, and attempt to take to lock. 53 */ 54 int drm_legacy_lock(struct drm_device *dev, void *data, 55 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 if (drm_core_check_feature(dev, DRIVER_MODESET)) 63 return -EINVAL; 64 65 ++file_priv->lock_count; 66 67 if (lock->context == DRM_KERNEL_CONTEXT) { 68 DRM_ERROR("Process %d using kernel context %d\n", 69 task_pid_nr(current), lock->context); 70 return -EINVAL; 71 } 72 73 DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", 74 lock->context, task_pid_nr(current), 75 master->lock.hw_lock->lock, lock->flags); 76 77 add_wait_queue(&master->lock.lock_queue, &entry); 78 spin_lock_bh(&master->lock.spinlock); 79 master->lock.user_waiters++; 80 spin_unlock_bh(&master->lock.spinlock); 81 82 for (;;) { 83 __set_current_state(TASK_INTERRUPTIBLE); 84 if (!master->lock.hw_lock) { 85 /* Device has been unregistered */ 86 send_sig(SIGTERM, current, 0); 87 ret = -EINTR; 88 break; 89 } 90 if (drm_lock_take(&master->lock, lock->context)) { 91 master->lock.file_priv = file_priv; 92 master->lock.lock_time = jiffies; 93 break; /* Got lock */ 94 } 95 96 /* Contention */ 97 mutex_unlock(&drm_global_mutex); 98 schedule(); 99 mutex_lock(&drm_global_mutex); 100 if (signal_pending(current)) { 101 ret = -EINTR; 102 break; 103 } 104 } 105 spin_lock_bh(&master->lock.spinlock); 106 master->lock.user_waiters--; 107 spin_unlock_bh(&master->lock.spinlock); 108 __set_current_state(TASK_RUNNING); 109 remove_wait_queue(&master->lock.lock_queue, &entry); 110 111 DRM_DEBUG("%d %s\n", lock->context, 112 ret ? "interrupted" : "has lock"); 113 if (ret) return ret; 114 115 /* don't set the block all signals on the master process for now 116 * really probably not the correct answer but lets us debug xkb 117 * xserver for now */ 118 if (!file_priv->is_master) { 119 dev->sigdata.context = lock->context; 120 dev->sigdata.lock = master->lock.hw_lock; 121 } 122 123 if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT)) 124 { 125 if (dev->driver->dma_quiescent(dev)) { 126 DRM_DEBUG("%d waiting for DMA quiescent\n", 127 lock->context); 128 return -EBUSY; 129 } 130 } 131 132 return 0; 133 } 134 135 /** 136 * Unlock ioctl. 137 * 138 * \param inode device inode. 139 * \param file_priv DRM file private. 140 * \param cmd command. 141 * \param arg user argument, pointing to a drm_lock structure. 142 * \return zero on success or negative number on failure. 143 * 144 * Transfer and free the lock. 145 */ 146 int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) 147 { 148 struct drm_lock *lock = data; 149 struct drm_master *master = file_priv->master; 150 151 if (drm_core_check_feature(dev, DRIVER_MODESET)) 152 return -EINVAL; 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_legacy_lock_free(&master->lock, lock->context)) { 161 /* FIXME: Should really bail out here. */ 162 } 163 164 return 0; 165 } 166 167 /** 168 * Take the heavyweight lock. 169 * 170 * \param lock lock pointer. 171 * \param context locking context. 172 * \return one if the lock is held, or zero otherwise. 173 * 174 * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction. 175 */ 176 static 177 int drm_lock_take(struct drm_lock_data *lock_data, 178 unsigned int context) 179 { 180 unsigned int old, new, prev; 181 volatile unsigned int *lock = &lock_data->hw_lock->lock; 182 183 spin_lock_bh(&lock_data->spinlock); 184 do { 185 old = *lock; 186 if (old & _DRM_LOCK_HELD) 187 new = old | _DRM_LOCK_CONT; 188 else { 189 new = context | _DRM_LOCK_HELD | 190 ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ? 191 _DRM_LOCK_CONT : 0); 192 } 193 prev = cmpxchg(lock, old, new); 194 } while (prev != old); 195 spin_unlock_bh(&lock_data->spinlock); 196 197 if (_DRM_LOCKING_CONTEXT(old) == context) { 198 if (old & _DRM_LOCK_HELD) { 199 if (context != DRM_KERNEL_CONTEXT) { 200 DRM_ERROR("%d holds heavyweight lock\n", 201 context); 202 } 203 return 0; 204 } 205 } 206 207 if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) { 208 /* Have lock */ 209 return 1; 210 } 211 return 0; 212 } 213 214 /** 215 * This takes a lock forcibly and hands it to context. Should ONLY be used 216 * inside *_unlock to give lock to kernel before calling *_dma_schedule. 217 * 218 * \param dev DRM device. 219 * \param lock lock pointer. 220 * \param context locking context. 221 * \return always one. 222 * 223 * Resets the lock file pointer. 224 * Marks the lock as held by the given context, via the \p cmpxchg instruction. 225 */ 226 static int drm_lock_transfer(struct drm_lock_data *lock_data, 227 unsigned int context) 228 { 229 unsigned int old, new, prev; 230 volatile unsigned int *lock = &lock_data->hw_lock->lock; 231 232 lock_data->file_priv = NULL; 233 do { 234 old = *lock; 235 new = context | _DRM_LOCK_HELD; 236 prev = cmpxchg(lock, old, new); 237 } while (prev != old); 238 return 1; 239 } 240 241 /** 242 * Free lock. 243 * 244 * \param dev DRM device. 245 * \param lock lock. 246 * \param context context. 247 * 248 * Resets the lock file pointer. 249 * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task 250 * waiting on the lock queue. 251 */ 252 int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context) 253 { 254 unsigned int old, new, prev; 255 volatile unsigned int *lock = &lock_data->hw_lock->lock; 256 257 spin_lock_bh(&lock_data->spinlock); 258 if (lock_data->kernel_waiters != 0) { 259 drm_lock_transfer(lock_data, 0); 260 lock_data->idle_has_lock = 1; 261 spin_unlock_bh(&lock_data->spinlock); 262 return 1; 263 } 264 spin_unlock_bh(&lock_data->spinlock); 265 266 do { 267 old = *lock; 268 new = _DRM_LOCKING_CONTEXT(old); 269 prev = cmpxchg(lock, old, new); 270 } while (prev != old); 271 272 if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { 273 DRM_ERROR("%d freed heavyweight lock held by %d\n", 274 context, _DRM_LOCKING_CONTEXT(old)); 275 return 1; 276 } 277 wake_up_interruptible(&lock_data->lock_queue); 278 return 0; 279 } 280 281 /** 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 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