| 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_notifier(void *priv); |
| 42 | |
| 43 | static int drm_lock_take(struct drm_lock_data *lock_data, unsigned int context); |
| 44 | |
| 45 | /** |
| 46 | * Lock ioctl. |
| 47 | * |
| 48 | * \param inode device inode. |
| 49 | * \param file_priv DRM file private. |
| 50 | * \param cmd command. |
| 51 | * \param arg user argument, pointing to a drm_lock structure. |
| 52 | * \return zero on success or negative number on failure. |
| 53 | * |
| 54 | * Add the current task to the lock wait queue, and attempt to take to lock. |
| 55 | */ |
| 56 | int drm_legacy_lock(struct drm_device *dev, void *data, |
| 57 | struct drm_file *file_priv) |
| 58 | { |
| 59 | DECLARE_WAITQUEUE(entry, current); |
| 60 | struct drm_lock *lock = data; |
| 61 | struct drm_master *master = file_priv->master; |
| 62 | int ret = 0; |
| 63 | |
| 64 | if (drm_core_check_feature(dev, DRIVER_MODESET)) |
| 65 | return -EINVAL; |
| 66 | |
| 67 | ++file_priv->lock_count; |
| 68 | |
| 69 | if (lock->context == DRM_KERNEL_CONTEXT) { |
| 70 | DRM_ERROR("Process %d using kernel context %d\n", |
| 71 | task_pid_nr(current), lock->context); |
| 72 | return -EINVAL; |
| 73 | } |
| 74 | |
| 75 | DRM_DEBUG("%d (pid %d) requests lock (0x%08x), flags = 0x%08x\n", |
| 76 | lock->context, task_pid_nr(current), |
| 77 | master->lock.hw_lock->lock, lock->flags); |
| 78 | |
| 79 | add_wait_queue(&master->lock.lock_queue, &entry); |
| 80 | spin_lock_bh(&master->lock.spinlock); |
| 81 | master->lock.user_waiters++; |
| 82 | spin_unlock_bh(&master->lock.spinlock); |
| 83 | |
| 84 | for (;;) { |
| 85 | __set_current_state(TASK_INTERRUPTIBLE); |
| 86 | if (!master->lock.hw_lock) { |
| 87 | /* Device has been unregistered */ |
| 88 | send_sig(SIGTERM, current, 0); |
| 89 | ret = -EINTR; |
| 90 | break; |
| 91 | } |
| 92 | if (drm_lock_take(&master->lock, lock->context)) { |
| 93 | master->lock.file_priv = file_priv; |
| 94 | master->lock.lock_time = jiffies; |
| 95 | break; /* Got lock */ |
| 96 | } |
| 97 | |
| 98 | /* Contention */ |
| 99 | mutex_unlock(&drm_global_mutex); |
| 100 | schedule(); |
| 101 | mutex_lock(&drm_global_mutex); |
| 102 | if (signal_pending(current)) { |
| 103 | ret = -EINTR; |
| 104 | break; |
| 105 | } |
| 106 | } |
| 107 | spin_lock_bh(&master->lock.spinlock); |
| 108 | master->lock.user_waiters--; |
| 109 | spin_unlock_bh(&master->lock.spinlock); |
| 110 | __set_current_state(TASK_RUNNING); |
| 111 | remove_wait_queue(&master->lock.lock_queue, &entry); |
| 112 | |
| 113 | DRM_DEBUG("%d %s\n", lock->context, |
| 114 | ret ? "interrupted" : "has lock"); |
| 115 | if (ret) return ret; |
| 116 | |
| 117 | /* don't set the block all signals on the master process for now |
| 118 | * really probably not the correct answer but lets us debug xkb |
| 119 | * xserver for now */ |
| 120 | if (!file_priv->is_master) { |
| 121 | sigemptyset(&dev->sigmask); |
| 122 | sigaddset(&dev->sigmask, SIGSTOP); |
| 123 | sigaddset(&dev->sigmask, SIGTSTP); |
| 124 | sigaddset(&dev->sigmask, SIGTTIN); |
| 125 | sigaddset(&dev->sigmask, SIGTTOU); |
| 126 | dev->sigdata.context = lock->context; |
| 127 | dev->sigdata.lock = master->lock.hw_lock; |
| 128 | block_all_signals(drm_notifier, dev, &dev->sigmask); |
| 129 | } |
| 130 | |
| 131 | if (dev->driver->dma_quiescent && (lock->flags & _DRM_LOCK_QUIESCENT)) |
| 132 | { |
| 133 | if (dev->driver->dma_quiescent(dev)) { |
| 134 | DRM_DEBUG("%d waiting for DMA quiescent\n", |
| 135 | lock->context); |
| 136 | return -EBUSY; |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | return 0; |
| 141 | } |
| 142 | |
| 143 | /** |
| 144 | * Unlock ioctl. |
| 145 | * |
| 146 | * \param inode device inode. |
| 147 | * \param file_priv DRM file private. |
| 148 | * \param cmd command. |
| 149 | * \param arg user argument, pointing to a drm_lock structure. |
| 150 | * \return zero on success or negative number on failure. |
| 151 | * |
| 152 | * Transfer and free the lock. |
| 153 | */ |
| 154 | int drm_legacy_unlock(struct drm_device *dev, void *data, struct drm_file *file_priv) |
| 155 | { |
| 156 | struct drm_lock *lock = data; |
| 157 | struct drm_master *master = file_priv->master; |
| 158 | |
| 159 | if (drm_core_check_feature(dev, DRIVER_MODESET)) |
| 160 | return -EINVAL; |
| 161 | |
| 162 | if (lock->context == DRM_KERNEL_CONTEXT) { |
| 163 | DRM_ERROR("Process %d using kernel context %d\n", |
| 164 | task_pid_nr(current), lock->context); |
| 165 | return -EINVAL; |
| 166 | } |
| 167 | |
| 168 | if (drm_legacy_lock_free(&master->lock, lock->context)) { |
| 169 | /* FIXME: Should really bail out here. */ |
| 170 | } |
| 171 | |
| 172 | unblock_all_signals(); |
| 173 | return 0; |
| 174 | } |
| 175 | |
| 176 | /** |
| 177 | * Take the heavyweight lock. |
| 178 | * |
| 179 | * \param lock lock pointer. |
| 180 | * \param context locking context. |
| 181 | * \return one if the lock is held, or zero otherwise. |
| 182 | * |
| 183 | * Attempt to mark the lock as held by the given context, via the \p cmpxchg instruction. |
| 184 | */ |
| 185 | static |
| 186 | int drm_lock_take(struct drm_lock_data *lock_data, |
| 187 | unsigned int context) |
| 188 | { |
| 189 | unsigned int old, new, prev; |
| 190 | volatile unsigned int *lock = &lock_data->hw_lock->lock; |
| 191 | |
| 192 | spin_lock_bh(&lock_data->spinlock); |
| 193 | do { |
| 194 | old = *lock; |
| 195 | if (old & _DRM_LOCK_HELD) |
| 196 | new = old | _DRM_LOCK_CONT; |
| 197 | else { |
| 198 | new = context | _DRM_LOCK_HELD | |
| 199 | ((lock_data->user_waiters + lock_data->kernel_waiters > 1) ? |
| 200 | _DRM_LOCK_CONT : 0); |
| 201 | } |
| 202 | prev = cmpxchg(lock, old, new); |
| 203 | } while (prev != old); |
| 204 | spin_unlock_bh(&lock_data->spinlock); |
| 205 | |
| 206 | if (_DRM_LOCKING_CONTEXT(old) == context) { |
| 207 | if (old & _DRM_LOCK_HELD) { |
| 208 | if (context != DRM_KERNEL_CONTEXT) { |
| 209 | DRM_ERROR("%d holds heavyweight lock\n", |
| 210 | context); |
| 211 | } |
| 212 | return 0; |
| 213 | } |
| 214 | } |
| 215 | |
| 216 | if ((_DRM_LOCKING_CONTEXT(new)) == context && (new & _DRM_LOCK_HELD)) { |
| 217 | /* Have lock */ |
| 218 | return 1; |
| 219 | } |
| 220 | return 0; |
| 221 | } |
| 222 | |
| 223 | /** |
| 224 | * This takes a lock forcibly and hands it to context. Should ONLY be used |
| 225 | * inside *_unlock to give lock to kernel before calling *_dma_schedule. |
| 226 | * |
| 227 | * \param dev DRM device. |
| 228 | * \param lock lock pointer. |
| 229 | * \param context locking context. |
| 230 | * \return always one. |
| 231 | * |
| 232 | * Resets the lock file pointer. |
| 233 | * Marks the lock as held by the given context, via the \p cmpxchg instruction. |
| 234 | */ |
| 235 | static int drm_lock_transfer(struct drm_lock_data *lock_data, |
| 236 | unsigned int context) |
| 237 | { |
| 238 | unsigned int old, new, prev; |
| 239 | volatile unsigned int *lock = &lock_data->hw_lock->lock; |
| 240 | |
| 241 | lock_data->file_priv = NULL; |
| 242 | do { |
| 243 | old = *lock; |
| 244 | new = context | _DRM_LOCK_HELD; |
| 245 | prev = cmpxchg(lock, old, new); |
| 246 | } while (prev != old); |
| 247 | return 1; |
| 248 | } |
| 249 | |
| 250 | /** |
| 251 | * Free lock. |
| 252 | * |
| 253 | * \param dev DRM device. |
| 254 | * \param lock lock. |
| 255 | * \param context context. |
| 256 | * |
| 257 | * Resets the lock file pointer. |
| 258 | * Marks the lock as not held, via the \p cmpxchg instruction. Wakes any task |
| 259 | * waiting on the lock queue. |
| 260 | */ |
| 261 | int drm_legacy_lock_free(struct drm_lock_data *lock_data, unsigned int context) |
| 262 | { |
| 263 | unsigned int old, new, prev; |
| 264 | volatile unsigned int *lock = &lock_data->hw_lock->lock; |
| 265 | |
| 266 | spin_lock_bh(&lock_data->spinlock); |
| 267 | if (lock_data->kernel_waiters != 0) { |
| 268 | drm_lock_transfer(lock_data, 0); |
| 269 | lock_data->idle_has_lock = 1; |
| 270 | spin_unlock_bh(&lock_data->spinlock); |
| 271 | return 1; |
| 272 | } |
| 273 | spin_unlock_bh(&lock_data->spinlock); |
| 274 | |
| 275 | do { |
| 276 | old = *lock; |
| 277 | new = _DRM_LOCKING_CONTEXT(old); |
| 278 | prev = cmpxchg(lock, old, new); |
| 279 | } while (prev != old); |
| 280 | |
| 281 | if (_DRM_LOCK_IS_HELD(old) && _DRM_LOCKING_CONTEXT(old) != context) { |
| 282 | DRM_ERROR("%d freed heavyweight lock held by %d\n", |
| 283 | context, _DRM_LOCKING_CONTEXT(old)); |
| 284 | return 1; |
| 285 | } |
| 286 | wake_up_interruptible(&lock_data->lock_queue); |
| 287 | return 0; |
| 288 | } |
| 289 | |
| 290 | /** |
| 291 | * If we get here, it means that the process has called DRM_IOCTL_LOCK |
| 292 | * without calling DRM_IOCTL_UNLOCK. |
| 293 | * |
| 294 | * If the lock is not held, then let the signal proceed as usual. If the lock |
| 295 | * is held, then set the contended flag and keep the signal blocked. |
| 296 | * |
| 297 | * \param priv pointer to a drm_device structure. |
| 298 | * \return one if the signal should be delivered normally, or zero if the |
| 299 | * signal should be blocked. |
| 300 | */ |
| 301 | static int drm_notifier(void *priv) |
| 302 | { |
| 303 | struct drm_device *dev = priv; |
| 304 | struct drm_hw_lock *lock = dev->sigdata.lock; |
| 305 | unsigned int old, new, prev; |
| 306 | |
| 307 | /* Allow signal delivery if lock isn't held */ |
| 308 | if (!lock || !_DRM_LOCK_IS_HELD(lock->lock) |
| 309 | || _DRM_LOCKING_CONTEXT(lock->lock) != dev->sigdata.context) |
| 310 | return 1; |
| 311 | |
| 312 | /* Otherwise, set flag to force call to |
| 313 | drmUnlock */ |
| 314 | do { |
| 315 | old = lock->lock; |
| 316 | new = old | _DRM_LOCK_CONT; |
| 317 | prev = cmpxchg(&lock->lock, old, new); |
| 318 | } while (prev != old); |
| 319 | return 0; |
| 320 | } |
| 321 | |
| 322 | /** |
| 323 | * This function returns immediately and takes the hw lock |
| 324 | * with the kernel context if it is free, otherwise it gets the highest priority when and if |
| 325 | * it is eventually released. |
| 326 | * |
| 327 | * This guarantees that the kernel will _eventually_ have the lock _unless_ it is held |
| 328 | * by a blocked process. (In the latter case an explicit wait for the hardware lock would cause |
| 329 | * a deadlock, which is why the "idlelock" was invented). |
| 330 | * |
| 331 | * This should be sufficient to wait for GPU idle without |
| 332 | * having to worry about starvation. |
| 333 | */ |
| 334 | |
| 335 | void drm_legacy_idlelock_take(struct drm_lock_data *lock_data) |
| 336 | { |
| 337 | int ret; |
| 338 | |
| 339 | spin_lock_bh(&lock_data->spinlock); |
| 340 | lock_data->kernel_waiters++; |
| 341 | if (!lock_data->idle_has_lock) { |
| 342 | |
| 343 | spin_unlock_bh(&lock_data->spinlock); |
| 344 | ret = drm_lock_take(lock_data, DRM_KERNEL_CONTEXT); |
| 345 | spin_lock_bh(&lock_data->spinlock); |
| 346 | |
| 347 | if (ret == 1) |
| 348 | lock_data->idle_has_lock = 1; |
| 349 | } |
| 350 | spin_unlock_bh(&lock_data->spinlock); |
| 351 | } |
| 352 | EXPORT_SYMBOL(drm_legacy_idlelock_take); |
| 353 | |
| 354 | void drm_legacy_idlelock_release(struct drm_lock_data *lock_data) |
| 355 | { |
| 356 | unsigned int old, prev; |
| 357 | volatile unsigned int *lock = &lock_data->hw_lock->lock; |
| 358 | |
| 359 | spin_lock_bh(&lock_data->spinlock); |
| 360 | if (--lock_data->kernel_waiters == 0) { |
| 361 | if (lock_data->idle_has_lock) { |
| 362 | do { |
| 363 | old = *lock; |
| 364 | prev = cmpxchg(lock, old, DRM_KERNEL_CONTEXT); |
| 365 | } while (prev != old); |
| 366 | wake_up_interruptible(&lock_data->lock_queue); |
| 367 | lock_data->idle_has_lock = 0; |
| 368 | } |
| 369 | } |
| 370 | spin_unlock_bh(&lock_data->spinlock); |
| 371 | } |
| 372 | EXPORT_SYMBOL(drm_legacy_idlelock_release); |
| 373 | |
| 374 | int drm_legacy_i_have_hw_lock(struct drm_device *dev, |
| 375 | struct drm_file *file_priv) |
| 376 | { |
| 377 | struct drm_master *master = file_priv->master; |
| 378 | return (file_priv->lock_count && master->lock.hw_lock && |
| 379 | _DRM_LOCK_IS_HELD(master->lock.hw_lock->lock) && |
| 380 | master->lock.file_priv == file_priv); |
| 381 | } |