| 1 | /* |
| 2 | * Header file for reservations for dma-buf and ttm |
| 3 | * |
| 4 | * Copyright(C) 2011 Linaro Limited. All rights reserved. |
| 5 | * Copyright (C) 2012-2013 Canonical Ltd |
| 6 | * Copyright (C) 2012 Texas Instruments |
| 7 | * |
| 8 | * Authors: |
| 9 | * Rob Clark <robdclark@gmail.com> |
| 10 | * Maarten Lankhorst <maarten.lankhorst@canonical.com> |
| 11 | * Thomas Hellstrom <thellstrom-at-vmware-dot-com> |
| 12 | * |
| 13 | * Based on bo.c which bears the following copyright notice, |
| 14 | * but is dual licensed: |
| 15 | * |
| 16 | * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA |
| 17 | * All Rights Reserved. |
| 18 | * |
| 19 | * Permission is hereby granted, free of charge, to any person obtaining a |
| 20 | * copy of this software and associated documentation files (the |
| 21 | * "Software"), to deal in the Software without restriction, including |
| 22 | * without limitation the rights to use, copy, modify, merge, publish, |
| 23 | * distribute, sub license, and/or sell copies of the Software, and to |
| 24 | * permit persons to whom the Software is furnished to do so, subject to |
| 25 | * the following conditions: |
| 26 | * |
| 27 | * The above copyright notice and this permission notice (including the |
| 28 | * next paragraph) shall be included in all copies or substantial portions |
| 29 | * of the Software. |
| 30 | * |
| 31 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 32 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 33 | * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL |
| 34 | * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, |
| 35 | * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR |
| 36 | * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE |
| 37 | * USE OR OTHER DEALINGS IN THE SOFTWARE. |
| 38 | */ |
| 39 | #ifndef _LINUX_RESERVATION_H |
| 40 | #define _LINUX_RESERVATION_H |
| 41 | |
| 42 | #include <linux/ww_mutex.h> |
| 43 | #include <linux/dma-fence.h> |
| 44 | #include <linux/slab.h> |
| 45 | #include <linux/seqlock.h> |
| 46 | #include <linux/rcupdate.h> |
| 47 | |
| 48 | extern struct ww_class reservation_ww_class; |
| 49 | |
| 50 | /** |
| 51 | * struct dma_resv_list - a list of shared fences |
| 52 | * @rcu: for internal use |
| 53 | * @shared_count: table of shared fences |
| 54 | * @shared_max: for growing shared fence table |
| 55 | * @shared: shared fence table |
| 56 | */ |
| 57 | struct dma_resv_list { |
| 58 | struct rcu_head rcu; |
| 59 | u32 shared_count, shared_max; |
| 60 | struct dma_fence __rcu *shared[]; |
| 61 | }; |
| 62 | |
| 63 | /** |
| 64 | * struct dma_resv - a reservation object manages fences for a buffer |
| 65 | * |
| 66 | * There are multiple uses for this, with sometimes slightly different rules in |
| 67 | * how the fence slots are used. |
| 68 | * |
| 69 | * One use is to synchronize cross-driver access to a struct dma_buf, either for |
| 70 | * dynamic buffer management or just to handle implicit synchronization between |
| 71 | * different users of the buffer in userspace. See &dma_buf.resv for a more |
| 72 | * in-depth discussion. |
| 73 | * |
| 74 | * The other major use is to manage access and locking within a driver in a |
| 75 | * buffer based memory manager. struct ttm_buffer_object is the canonical |
| 76 | * example here, since this is where reservation objects originated from. But |
| 77 | * use in drivers is spreading and some drivers also manage struct |
| 78 | * drm_gem_object with the same scheme. |
| 79 | */ |
| 80 | struct dma_resv { |
| 81 | /** |
| 82 | * @lock: |
| 83 | * |
| 84 | * Update side lock. Don't use directly, instead use the wrapper |
| 85 | * functions like dma_resv_lock() and dma_resv_unlock(). |
| 86 | * |
| 87 | * Drivers which use the reservation object to manage memory dynamically |
| 88 | * also use this lock to protect buffer object state like placement, |
| 89 | * allocation policies or throughout command submission. |
| 90 | */ |
| 91 | struct ww_mutex lock; |
| 92 | |
| 93 | /** |
| 94 | * @seq: |
| 95 | * |
| 96 | * Sequence count for managing RCU read-side synchronization, allows |
| 97 | * read-only access to @fence_excl and @fence while ensuring we take a |
| 98 | * consistent snapshot. |
| 99 | */ |
| 100 | seqcount_ww_mutex_t seq; |
| 101 | |
| 102 | /** |
| 103 | * @fence_excl: |
| 104 | * |
| 105 | * The exclusive fence, if there is one currently. |
| 106 | * |
| 107 | * There are two ways to update this fence: |
| 108 | * |
| 109 | * - First by calling dma_resv_add_excl_fence(), which replaces all |
| 110 | * fences attached to the reservation object. To guarantee that no |
| 111 | * fences are lost, this new fence must signal only after all previous |
| 112 | * fences, both shared and exclusive, have signalled. In some cases it |
| 113 | * is convenient to achieve that by attaching a struct dma_fence_array |
| 114 | * with all the new and old fences. |
| 115 | * |
| 116 | * - Alternatively the fence can be set directly, which leaves the |
| 117 | * shared fences unchanged. To guarantee that no fences are lost, this |
| 118 | * new fence must signal only after the previous exclusive fence has |
| 119 | * signalled. Since the shared fences are staying intact, it is not |
| 120 | * necessary to maintain any ordering against those. If semantically |
| 121 | * only a new access is added without actually treating the previous |
| 122 | * one as a dependency the exclusive fences can be strung together |
| 123 | * using struct dma_fence_chain. |
| 124 | * |
| 125 | * Note that actual semantics of what an exclusive or shared fence mean |
| 126 | * is defined by the user, for reservation objects shared across drivers |
| 127 | * see &dma_buf.resv. |
| 128 | */ |
| 129 | struct dma_fence __rcu *fence_excl; |
| 130 | |
| 131 | /** |
| 132 | * @fence: |
| 133 | * |
| 134 | * List of current shared fences. |
| 135 | * |
| 136 | * There are no ordering constraints of shared fences against the |
| 137 | * exclusive fence slot. If a waiter needs to wait for all access, it |
| 138 | * has to wait for both sets of fences to signal. |
| 139 | * |
| 140 | * A new fence is added by calling dma_resv_add_shared_fence(). Since |
| 141 | * this often needs to be done past the point of no return in command |
| 142 | * submission it cannot fail, and therefore sufficient slots need to be |
| 143 | * reserved by calling dma_resv_reserve_shared(). |
| 144 | * |
| 145 | * Note that actual semantics of what an exclusive or shared fence mean |
| 146 | * is defined by the user, for reservation objects shared across drivers |
| 147 | * see &dma_buf.resv. |
| 148 | */ |
| 149 | struct dma_resv_list __rcu *fence; |
| 150 | }; |
| 151 | |
| 152 | /** |
| 153 | * struct dma_resv_iter - current position into the dma_resv fences |
| 154 | * |
| 155 | * Don't touch this directly in the driver, use the accessor function instead. |
| 156 | */ |
| 157 | struct dma_resv_iter { |
| 158 | /** @obj: The dma_resv object we iterate over */ |
| 159 | struct dma_resv *obj; |
| 160 | |
| 161 | /** @all_fences: If all fences should be returned */ |
| 162 | bool all_fences; |
| 163 | |
| 164 | /** @fence: the currently handled fence */ |
| 165 | struct dma_fence *fence; |
| 166 | |
| 167 | /** @seq: sequence number to check for modifications */ |
| 168 | unsigned int seq; |
| 169 | |
| 170 | /** @index: index into the shared fences */ |
| 171 | unsigned int index; |
| 172 | |
| 173 | /** @fences: the shared fences; private, *MUST* not dereference */ |
| 174 | struct dma_resv_list *fences; |
| 175 | |
| 176 | /** @shared_count: number of shared fences */ |
| 177 | unsigned int shared_count; |
| 178 | |
| 179 | /** @is_restarted: true if this is the first returned fence */ |
| 180 | bool is_restarted; |
| 181 | }; |
| 182 | |
| 183 | struct dma_fence *dma_resv_iter_first_unlocked(struct dma_resv_iter *cursor); |
| 184 | struct dma_fence *dma_resv_iter_next_unlocked(struct dma_resv_iter *cursor); |
| 185 | struct dma_fence *dma_resv_iter_first(struct dma_resv_iter *cursor); |
| 186 | struct dma_fence *dma_resv_iter_next(struct dma_resv_iter *cursor); |
| 187 | |
| 188 | /** |
| 189 | * dma_resv_iter_begin - initialize a dma_resv_iter object |
| 190 | * @cursor: The dma_resv_iter object to initialize |
| 191 | * @obj: The dma_resv object which we want to iterate over |
| 192 | * @all_fences: If all fences should be returned or just the exclusive one |
| 193 | */ |
| 194 | static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor, |
| 195 | struct dma_resv *obj, |
| 196 | bool all_fences) |
| 197 | { |
| 198 | cursor->obj = obj; |
| 199 | cursor->all_fences = all_fences; |
| 200 | cursor->fence = NULL; |
| 201 | } |
| 202 | |
| 203 | /** |
| 204 | * dma_resv_iter_end - cleanup a dma_resv_iter object |
| 205 | * @cursor: the dma_resv_iter object which should be cleaned up |
| 206 | * |
| 207 | * Make sure that the reference to the fence in the cursor is properly |
| 208 | * dropped. |
| 209 | */ |
| 210 | static inline void dma_resv_iter_end(struct dma_resv_iter *cursor) |
| 211 | { |
| 212 | dma_fence_put(cursor->fence); |
| 213 | } |
| 214 | |
| 215 | /** |
| 216 | * dma_resv_iter_is_exclusive - test if the current fence is the exclusive one |
| 217 | * @cursor: the cursor of the current position |
| 218 | * |
| 219 | * Returns true if the currently returned fence is the exclusive one. |
| 220 | */ |
| 221 | static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter *cursor) |
| 222 | { |
| 223 | return cursor->index == 0; |
| 224 | } |
| 225 | |
| 226 | /** |
| 227 | * dma_resv_iter_is_restarted - test if this is the first fence after a restart |
| 228 | * @cursor: the cursor with the current position |
| 229 | * |
| 230 | * Return true if this is the first fence in an iteration after a restart. |
| 231 | */ |
| 232 | static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor) |
| 233 | { |
| 234 | return cursor->is_restarted; |
| 235 | } |
| 236 | |
| 237 | /** |
| 238 | * dma_resv_for_each_fence_unlocked - unlocked fence iterator |
| 239 | * @cursor: a struct dma_resv_iter pointer |
| 240 | * @fence: the current fence |
| 241 | * |
| 242 | * Iterate over the fences in a struct dma_resv object without holding the |
| 243 | * &dma_resv.lock and using RCU instead. The cursor needs to be initialized |
| 244 | * with dma_resv_iter_begin() and cleaned up with dma_resv_iter_end(). Inside |
| 245 | * the iterator a reference to the dma_fence is held and the RCU lock dropped. |
| 246 | * When the dma_resv is modified the iteration starts over again. |
| 247 | */ |
| 248 | #define dma_resv_for_each_fence_unlocked(cursor, fence) \ |
| 249 | for (fence = dma_resv_iter_first_unlocked(cursor); \ |
| 250 | fence; fence = dma_resv_iter_next_unlocked(cursor)) |
| 251 | |
| 252 | /** |
| 253 | * dma_resv_for_each_fence - fence iterator |
| 254 | * @cursor: a struct dma_resv_iter pointer |
| 255 | * @obj: a dma_resv object pointer |
| 256 | * @all_fences: true if all fences should be returned |
| 257 | * @fence: the current fence |
| 258 | * |
| 259 | * Iterate over the fences in a struct dma_resv object while holding the |
| 260 | * &dma_resv.lock. @all_fences controls if the shared fences are returned as |
| 261 | * well. The cursor initialisation is part of the iterator and the fence stays |
| 262 | * valid as long as the lock is held and so no extra reference to the fence is |
| 263 | * taken. |
| 264 | */ |
| 265 | #define dma_resv_for_each_fence(cursor, obj, all_fences, fence) \ |
| 266 | for (dma_resv_iter_begin(cursor, obj, all_fences), \ |
| 267 | fence = dma_resv_iter_first(cursor); fence; \ |
| 268 | fence = dma_resv_iter_next(cursor)) |
| 269 | |
| 270 | #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base) |
| 271 | #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base) |
| 272 | |
| 273 | #ifdef CONFIG_DEBUG_MUTEXES |
| 274 | void dma_resv_reset_shared_max(struct dma_resv *obj); |
| 275 | #else |
| 276 | static inline void dma_resv_reset_shared_max(struct dma_resv *obj) {} |
| 277 | #endif |
| 278 | |
| 279 | /** |
| 280 | * dma_resv_lock - lock the reservation object |
| 281 | * @obj: the reservation object |
| 282 | * @ctx: the locking context |
| 283 | * |
| 284 | * Locks the reservation object for exclusive access and modification. Note, |
| 285 | * that the lock is only against other writers, readers will run concurrently |
| 286 | * with a writer under RCU. The seqlock is used to notify readers if they |
| 287 | * overlap with a writer. |
| 288 | * |
| 289 | * As the reservation object may be locked by multiple parties in an |
| 290 | * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle |
| 291 | * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation |
| 292 | * object may be locked by itself by passing NULL as @ctx. |
| 293 | * |
| 294 | * When a die situation is indicated by returning -EDEADLK all locks held by |
| 295 | * @ctx must be unlocked and then dma_resv_lock_slow() called on @obj. |
| 296 | * |
| 297 | * Unlocked by calling dma_resv_unlock(). |
| 298 | * |
| 299 | * See also dma_resv_lock_interruptible() for the interruptible variant. |
| 300 | */ |
| 301 | static inline int dma_resv_lock(struct dma_resv *obj, |
| 302 | struct ww_acquire_ctx *ctx) |
| 303 | { |
| 304 | return ww_mutex_lock(&obj->lock, ctx); |
| 305 | } |
| 306 | |
| 307 | /** |
| 308 | * dma_resv_lock_interruptible - lock the reservation object |
| 309 | * @obj: the reservation object |
| 310 | * @ctx: the locking context |
| 311 | * |
| 312 | * Locks the reservation object interruptible for exclusive access and |
| 313 | * modification. Note, that the lock is only against other writers, readers |
| 314 | * will run concurrently with a writer under RCU. The seqlock is used to |
| 315 | * notify readers if they overlap with a writer. |
| 316 | * |
| 317 | * As the reservation object may be locked by multiple parties in an |
| 318 | * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle |
| 319 | * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation |
| 320 | * object may be locked by itself by passing NULL as @ctx. |
| 321 | * |
| 322 | * When a die situation is indicated by returning -EDEADLK all locks held by |
| 323 | * @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on |
| 324 | * @obj. |
| 325 | * |
| 326 | * Unlocked by calling dma_resv_unlock(). |
| 327 | */ |
| 328 | static inline int dma_resv_lock_interruptible(struct dma_resv *obj, |
| 329 | struct ww_acquire_ctx *ctx) |
| 330 | { |
| 331 | return ww_mutex_lock_interruptible(&obj->lock, ctx); |
| 332 | } |
| 333 | |
| 334 | /** |
| 335 | * dma_resv_lock_slow - slowpath lock the reservation object |
| 336 | * @obj: the reservation object |
| 337 | * @ctx: the locking context |
| 338 | * |
| 339 | * Acquires the reservation object after a die case. This function |
| 340 | * will sleep until the lock becomes available. See dma_resv_lock() as |
| 341 | * well. |
| 342 | * |
| 343 | * See also dma_resv_lock_slow_interruptible() for the interruptible variant. |
| 344 | */ |
| 345 | static inline void dma_resv_lock_slow(struct dma_resv *obj, |
| 346 | struct ww_acquire_ctx *ctx) |
| 347 | { |
| 348 | ww_mutex_lock_slow(&obj->lock, ctx); |
| 349 | } |
| 350 | |
| 351 | /** |
| 352 | * dma_resv_lock_slow_interruptible - slowpath lock the reservation |
| 353 | * object, interruptible |
| 354 | * @obj: the reservation object |
| 355 | * @ctx: the locking context |
| 356 | * |
| 357 | * Acquires the reservation object interruptible after a die case. This function |
| 358 | * will sleep until the lock becomes available. See |
| 359 | * dma_resv_lock_interruptible() as well. |
| 360 | */ |
| 361 | static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj, |
| 362 | struct ww_acquire_ctx *ctx) |
| 363 | { |
| 364 | return ww_mutex_lock_slow_interruptible(&obj->lock, ctx); |
| 365 | } |
| 366 | |
| 367 | /** |
| 368 | * dma_resv_trylock - trylock the reservation object |
| 369 | * @obj: the reservation object |
| 370 | * |
| 371 | * Tries to lock the reservation object for exclusive access and modification. |
| 372 | * Note, that the lock is only against other writers, readers will run |
| 373 | * concurrently with a writer under RCU. The seqlock is used to notify readers |
| 374 | * if they overlap with a writer. |
| 375 | * |
| 376 | * Also note that since no context is provided, no deadlock protection is |
| 377 | * possible, which is also not needed for a trylock. |
| 378 | * |
| 379 | * Returns true if the lock was acquired, false otherwise. |
| 380 | */ |
| 381 | static inline bool __must_check dma_resv_trylock(struct dma_resv *obj) |
| 382 | { |
| 383 | return ww_mutex_trylock(&obj->lock, NULL); |
| 384 | } |
| 385 | |
| 386 | /** |
| 387 | * dma_resv_is_locked - is the reservation object locked |
| 388 | * @obj: the reservation object |
| 389 | * |
| 390 | * Returns true if the mutex is locked, false if unlocked. |
| 391 | */ |
| 392 | static inline bool dma_resv_is_locked(struct dma_resv *obj) |
| 393 | { |
| 394 | return ww_mutex_is_locked(&obj->lock); |
| 395 | } |
| 396 | |
| 397 | /** |
| 398 | * dma_resv_locking_ctx - returns the context used to lock the object |
| 399 | * @obj: the reservation object |
| 400 | * |
| 401 | * Returns the context used to lock a reservation object or NULL if no context |
| 402 | * was used or the object is not locked at all. |
| 403 | * |
| 404 | * WARNING: This interface is pretty horrible, but TTM needs it because it |
| 405 | * doesn't pass the struct ww_acquire_ctx around in some very long callchains. |
| 406 | * Everyone else just uses it to check whether they're holding a reservation or |
| 407 | * not. |
| 408 | */ |
| 409 | static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj) |
| 410 | { |
| 411 | return READ_ONCE(obj->lock.ctx); |
| 412 | } |
| 413 | |
| 414 | /** |
| 415 | * dma_resv_unlock - unlock the reservation object |
| 416 | * @obj: the reservation object |
| 417 | * |
| 418 | * Unlocks the reservation object following exclusive access. |
| 419 | */ |
| 420 | static inline void dma_resv_unlock(struct dma_resv *obj) |
| 421 | { |
| 422 | dma_resv_reset_shared_max(obj); |
| 423 | ww_mutex_unlock(&obj->lock); |
| 424 | } |
| 425 | |
| 426 | /** |
| 427 | * dma_resv_excl_fence - return the object's exclusive fence |
| 428 | * @obj: the reservation object |
| 429 | * |
| 430 | * Returns the exclusive fence (if any). Caller must either hold the objects |
| 431 | * through dma_resv_lock() or the RCU read side lock through rcu_read_lock(), |
| 432 | * or one of the variants of each |
| 433 | * |
| 434 | * RETURNS |
| 435 | * The exclusive fence or NULL |
| 436 | */ |
| 437 | static inline struct dma_fence * |
| 438 | dma_resv_excl_fence(struct dma_resv *obj) |
| 439 | { |
| 440 | return rcu_dereference_check(obj->fence_excl, dma_resv_held(obj)); |
| 441 | } |
| 442 | |
| 443 | /** |
| 444 | * dma_resv_shared_list - get the reservation object's shared fence list |
| 445 | * @obj: the reservation object |
| 446 | * |
| 447 | * Returns the shared fence list. Caller must either hold the objects |
| 448 | * through dma_resv_lock() or the RCU read side lock through rcu_read_lock(), |
| 449 | * or one of the variants of each |
| 450 | */ |
| 451 | static inline struct dma_resv_list *dma_resv_shared_list(struct dma_resv *obj) |
| 452 | { |
| 453 | return rcu_dereference_check(obj->fence, dma_resv_held(obj)); |
| 454 | } |
| 455 | |
| 456 | void dma_resv_init(struct dma_resv *obj); |
| 457 | void dma_resv_fini(struct dma_resv *obj); |
| 458 | int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences); |
| 459 | void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence); |
| 460 | void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence); |
| 461 | int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **pfence_excl, |
| 462 | unsigned *pshared_count, struct dma_fence ***pshared); |
| 463 | int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src); |
| 464 | long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr, |
| 465 | unsigned long timeout); |
| 466 | bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all); |
| 467 | void dma_resv_describe(struct dma_resv *obj, struct seq_file *seq); |
| 468 | |
| 469 | #endif /* _LINUX_RESERVATION_H */ |