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 #define dma_resv_held(obj) lockdep_is_held(&(obj)->lock.base) 153 #define dma_resv_assert_held(obj) lockdep_assert_held(&(obj)->lock.base) 154 155 #ifdef CONFIG_DEBUG_MUTEXES 156 void dma_resv_reset_shared_max(struct dma_resv *obj); 157 #else 158 static inline void dma_resv_reset_shared_max(struct dma_resv *obj) {} 159 #endif 160 161 /** 162 * dma_resv_lock - lock the reservation object 163 * @obj: the reservation object 164 * @ctx: the locking context 165 * 166 * Locks the reservation object for exclusive access and modification. Note, 167 * that the lock is only against other writers, readers will run concurrently 168 * with a writer under RCU. The seqlock is used to notify readers if they 169 * overlap with a writer. 170 * 171 * As the reservation object may be locked by multiple parties in an 172 * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle 173 * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation 174 * object may be locked by itself by passing NULL as @ctx. 175 * 176 * When a die situation is indicated by returning -EDEADLK all locks held by 177 * @ctx must be unlocked and then dma_resv_lock_slow() called on @obj. 178 * 179 * Unlocked by calling dma_resv_unlock(). 180 * 181 * See also dma_resv_lock_interruptible() for the interruptible variant. 182 */ 183 static inline int dma_resv_lock(struct dma_resv *obj, 184 struct ww_acquire_ctx *ctx) 185 { 186 return ww_mutex_lock(&obj->lock, ctx); 187 } 188 189 /** 190 * dma_resv_lock_interruptible - lock the reservation object 191 * @obj: the reservation object 192 * @ctx: the locking context 193 * 194 * Locks the reservation object interruptible for exclusive access and 195 * modification. Note, that the lock is only against other writers, readers 196 * will run concurrently with a writer under RCU. The seqlock is used to 197 * notify readers if they overlap with a writer. 198 * 199 * As the reservation object may be locked by multiple parties in an 200 * undefined order, a #ww_acquire_ctx is passed to unwind if a cycle 201 * is detected. See ww_mutex_lock() and ww_acquire_init(). A reservation 202 * object may be locked by itself by passing NULL as @ctx. 203 * 204 * When a die situation is indicated by returning -EDEADLK all locks held by 205 * @ctx must be unlocked and then dma_resv_lock_slow_interruptible() called on 206 * @obj. 207 * 208 * Unlocked by calling dma_resv_unlock(). 209 */ 210 static inline int dma_resv_lock_interruptible(struct dma_resv *obj, 211 struct ww_acquire_ctx *ctx) 212 { 213 return ww_mutex_lock_interruptible(&obj->lock, ctx); 214 } 215 216 /** 217 * dma_resv_lock_slow - slowpath lock the reservation object 218 * @obj: the reservation object 219 * @ctx: the locking context 220 * 221 * Acquires the reservation object after a die case. This function 222 * will sleep until the lock becomes available. See dma_resv_lock() as 223 * well. 224 * 225 * See also dma_resv_lock_slow_interruptible() for the interruptible variant. 226 */ 227 static inline void dma_resv_lock_slow(struct dma_resv *obj, 228 struct ww_acquire_ctx *ctx) 229 { 230 ww_mutex_lock_slow(&obj->lock, ctx); 231 } 232 233 /** 234 * dma_resv_lock_slow_interruptible - slowpath lock the reservation 235 * object, interruptible 236 * @obj: the reservation object 237 * @ctx: the locking context 238 * 239 * Acquires the reservation object interruptible after a die case. This function 240 * will sleep until the lock becomes available. See 241 * dma_resv_lock_interruptible() as well. 242 */ 243 static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj, 244 struct ww_acquire_ctx *ctx) 245 { 246 return ww_mutex_lock_slow_interruptible(&obj->lock, ctx); 247 } 248 249 /** 250 * dma_resv_trylock - trylock the reservation object 251 * @obj: the reservation object 252 * 253 * Tries to lock the reservation object for exclusive access and modification. 254 * Note, that the lock is only against other writers, readers will run 255 * concurrently with a writer under RCU. The seqlock is used to notify readers 256 * if they overlap with a writer. 257 * 258 * Also note that since no context is provided, no deadlock protection is 259 * possible, which is also not needed for a trylock. 260 * 261 * Returns true if the lock was acquired, false otherwise. 262 */ 263 static inline bool __must_check dma_resv_trylock(struct dma_resv *obj) 264 { 265 return ww_mutex_trylock(&obj->lock); 266 } 267 268 /** 269 * dma_resv_is_locked - is the reservation object locked 270 * @obj: the reservation object 271 * 272 * Returns true if the mutex is locked, false if unlocked. 273 */ 274 static inline bool dma_resv_is_locked(struct dma_resv *obj) 275 { 276 return ww_mutex_is_locked(&obj->lock); 277 } 278 279 /** 280 * dma_resv_locking_ctx - returns the context used to lock the object 281 * @obj: the reservation object 282 * 283 * Returns the context used to lock a reservation object or NULL if no context 284 * was used or the object is not locked at all. 285 * 286 * WARNING: This interface is pretty horrible, but TTM needs it because it 287 * doesn't pass the struct ww_acquire_ctx around in some very long callchains. 288 * Everyone else just uses it to check whether they're holding a reservation or 289 * not. 290 */ 291 static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj) 292 { 293 return READ_ONCE(obj->lock.ctx); 294 } 295 296 /** 297 * dma_resv_unlock - unlock the reservation object 298 * @obj: the reservation object 299 * 300 * Unlocks the reservation object following exclusive access. 301 */ 302 static inline void dma_resv_unlock(struct dma_resv *obj) 303 { 304 dma_resv_reset_shared_max(obj); 305 ww_mutex_unlock(&obj->lock); 306 } 307 308 /** 309 * dma_resv_excl_fence - return the object's exclusive fence 310 * @obj: the reservation object 311 * 312 * Returns the exclusive fence (if any). Caller must either hold the objects 313 * through dma_resv_lock() or the RCU read side lock through rcu_read_lock(), 314 * or one of the variants of each 315 * 316 * RETURNS 317 * The exclusive fence or NULL 318 */ 319 static inline struct dma_fence * 320 dma_resv_excl_fence(struct dma_resv *obj) 321 { 322 return rcu_dereference_check(obj->fence_excl, dma_resv_held(obj)); 323 } 324 325 /** 326 * dma_resv_get_excl_unlocked - get the reservation object's 327 * exclusive fence, without lock held. 328 * @obj: the reservation object 329 * 330 * If there is an exclusive fence, this atomically increments it's 331 * reference count and returns it. 332 * 333 * RETURNS 334 * The exclusive fence or NULL if none 335 */ 336 static inline struct dma_fence * 337 dma_resv_get_excl_unlocked(struct dma_resv *obj) 338 { 339 struct dma_fence *fence; 340 341 if (!rcu_access_pointer(obj->fence_excl)) 342 return NULL; 343 344 rcu_read_lock(); 345 fence = dma_fence_get_rcu_safe(&obj->fence_excl); 346 rcu_read_unlock(); 347 348 return fence; 349 } 350 351 /** 352 * dma_resv_shared_list - get the reservation object's shared fence list 353 * @obj: the reservation object 354 * 355 * Returns the shared fence list. Caller must either hold the objects 356 * through dma_resv_lock() or the RCU read side lock through rcu_read_lock(), 357 * or one of the variants of each 358 */ 359 static inline struct dma_resv_list *dma_resv_shared_list(struct dma_resv *obj) 360 { 361 return rcu_dereference_check(obj->fence, dma_resv_held(obj)); 362 } 363 364 void dma_resv_init(struct dma_resv *obj); 365 void dma_resv_fini(struct dma_resv *obj); 366 int dma_resv_reserve_shared(struct dma_resv *obj, unsigned int num_fences); 367 void dma_resv_add_shared_fence(struct dma_resv *obj, struct dma_fence *fence); 368 void dma_resv_add_excl_fence(struct dma_resv *obj, struct dma_fence *fence); 369 int dma_resv_get_fences(struct dma_resv *obj, struct dma_fence **pfence_excl, 370 unsigned *pshared_count, struct dma_fence ***pshared); 371 int dma_resv_copy_fences(struct dma_resv *dst, struct dma_resv *src); 372 long dma_resv_wait_timeout(struct dma_resv *obj, bool wait_all, bool intr, 373 unsigned long timeout); 374 bool dma_resv_test_signaled(struct dma_resv *obj, bool test_all); 375 376 #endif /* _LINUX_RESERVATION_H */ 377