2 * Header file for reservations for dma-buf and ttm
4 * Copyright(C) 2011 Linaro Limited. All rights reserved.
5 * Copyright (C) 2012-2013 Canonical Ltd
6 * Copyright (C) 2012 Texas Instruments
9 * Rob Clark <robdclark@gmail.com>
10 * Maarten Lankhorst <maarten.lankhorst@canonical.com>
11 * Thomas Hellstrom <thellstrom-at-vmware-dot-com>
13 * Based on bo.c which bears the following copyright notice,
14 * but is dual licensed:
16 * Copyright (c) 2006-2009 VMware, Inc., Palo Alto, CA., USA
17 * All Rights Reserved.
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21 * "Software"), to deal in the Software without restriction, including
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24 * permit persons to whom the Software is furnished to do so, subject to
25 * the following conditions:
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39 #ifndef _LINUX_RESERVATION_H
40 #define _LINUX_RESERVATION_H
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>
48 extern struct ww_class reservation_ww_class;
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
57 struct dma_resv_list {
59 u32 shared_count, shared_max;
60 struct dma_fence __rcu *shared[];
64 * struct dma_resv - a reservation object manages fences for a buffer
66 * There are multiple uses for this, with sometimes slightly different rules in
67 * how the fence slots are used.
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.
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.
84 * Update side lock. Don't use directly, instead use the wrapper
85 * functions like dma_resv_lock() and dma_resv_unlock().
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.
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.
100 seqcount_ww_mutex_t seq;
105 * The exclusive fence, if there is one currently.
107 * There are two ways to update this fence:
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.
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.
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
129 struct dma_fence __rcu *fence_excl;
134 * List of current shared fences.
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.
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().
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
149 struct dma_resv_list __rcu *fence;
153 * struct dma_resv_iter - current position into the dma_resv fences
155 * Don't touch this directly in the driver, use the accessor function instead.
157 struct dma_resv_iter {
158 /** @obj: The dma_resv object we iterate over */
159 struct dma_resv *obj;
161 /** @all_fences: If all fences should be returned */
164 /** @fence: the currently handled fence */
165 struct dma_fence *fence;
167 /** @seq: sequence number to check for modifications */
170 /** @index: index into the shared fences */
173 /** @fences: the shared fences; private, *MUST* not dereference */
174 struct dma_resv_list *fences;
176 /** @shared_count: number of shared fences */
177 unsigned int shared_count;
179 /** @is_restarted: true if this is the first returned fence */
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);
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
194 static inline void dma_resv_iter_begin(struct dma_resv_iter *cursor,
195 struct dma_resv *obj,
199 cursor->all_fences = all_fences;
200 cursor->fence = NULL;
204 * dma_resv_iter_end - cleanup a dma_resv_iter object
205 * @cursor: the dma_resv_iter object which should be cleaned up
207 * Make sure that the reference to the fence in the cursor is properly
210 static inline void dma_resv_iter_end(struct dma_resv_iter *cursor)
212 dma_fence_put(cursor->fence);
216 * dma_resv_iter_is_exclusive - test if the current fence is the exclusive one
217 * @cursor: the cursor of the current position
219 * Returns true if the currently returned fence is the exclusive one.
221 static inline bool dma_resv_iter_is_exclusive(struct dma_resv_iter *cursor)
223 return cursor->index == 0;
227 * dma_resv_iter_is_restarted - test if this is the first fence after a restart
228 * @cursor: the cursor with the current position
230 * Return true if this is the first fence in an iteration after a restart.
232 static inline bool dma_resv_iter_is_restarted(struct dma_resv_iter *cursor)
234 return cursor->is_restarted;
238 * dma_resv_for_each_fence_unlocked - unlocked fence iterator
239 * @cursor: a struct dma_resv_iter pointer
240 * @fence: the current fence
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.
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))
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
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
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))
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)
273 #ifdef CONFIG_DEBUG_MUTEXES
274 void dma_resv_reset_shared_max(struct dma_resv *obj);
276 static inline void dma_resv_reset_shared_max(struct dma_resv *obj) {}
280 * dma_resv_lock - lock the reservation object
281 * @obj: the reservation object
282 * @ctx: the locking context
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.
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.
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.
297 * Unlocked by calling dma_resv_unlock().
299 * See also dma_resv_lock_interruptible() for the interruptible variant.
301 static inline int dma_resv_lock(struct dma_resv *obj,
302 struct ww_acquire_ctx *ctx)
304 return ww_mutex_lock(&obj->lock, ctx);
308 * dma_resv_lock_interruptible - lock the reservation object
309 * @obj: the reservation object
310 * @ctx: the locking context
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.
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.
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
326 * Unlocked by calling dma_resv_unlock().
328 static inline int dma_resv_lock_interruptible(struct dma_resv *obj,
329 struct ww_acquire_ctx *ctx)
331 return ww_mutex_lock_interruptible(&obj->lock, ctx);
335 * dma_resv_lock_slow - slowpath lock the reservation object
336 * @obj: the reservation object
337 * @ctx: the locking context
339 * Acquires the reservation object after a die case. This function
340 * will sleep until the lock becomes available. See dma_resv_lock() as
343 * See also dma_resv_lock_slow_interruptible() for the interruptible variant.
345 static inline void dma_resv_lock_slow(struct dma_resv *obj,
346 struct ww_acquire_ctx *ctx)
348 ww_mutex_lock_slow(&obj->lock, ctx);
352 * dma_resv_lock_slow_interruptible - slowpath lock the reservation
353 * object, interruptible
354 * @obj: the reservation object
355 * @ctx: the locking context
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.
361 static inline int dma_resv_lock_slow_interruptible(struct dma_resv *obj,
362 struct ww_acquire_ctx *ctx)
364 return ww_mutex_lock_slow_interruptible(&obj->lock, ctx);
368 * dma_resv_trylock - trylock the reservation object
369 * @obj: the reservation object
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.
376 * Also note that since no context is provided, no deadlock protection is
377 * possible, which is also not needed for a trylock.
379 * Returns true if the lock was acquired, false otherwise.
381 static inline bool __must_check dma_resv_trylock(struct dma_resv *obj)
383 return ww_mutex_trylock(&obj->lock, NULL);
387 * dma_resv_is_locked - is the reservation object locked
388 * @obj: the reservation object
390 * Returns true if the mutex is locked, false if unlocked.
392 static inline bool dma_resv_is_locked(struct dma_resv *obj)
394 return ww_mutex_is_locked(&obj->lock);
398 * dma_resv_locking_ctx - returns the context used to lock the object
399 * @obj: the reservation object
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.
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
409 static inline struct ww_acquire_ctx *dma_resv_locking_ctx(struct dma_resv *obj)
411 return READ_ONCE(obj->lock.ctx);
415 * dma_resv_unlock - unlock the reservation object
416 * @obj: the reservation object
418 * Unlocks the reservation object following exclusive access.
420 static inline void dma_resv_unlock(struct dma_resv *obj)
422 dma_resv_reset_shared_max(obj);
423 ww_mutex_unlock(&obj->lock);
427 * dma_resv_excl_fence - return the object's exclusive fence
428 * @obj: the reservation object
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
435 * The exclusive fence or NULL
437 static inline struct dma_fence *
438 dma_resv_excl_fence(struct dma_resv *obj)
440 return rcu_dereference_check(obj->fence_excl, dma_resv_held(obj));
444 * dma_resv_shared_list - get the reservation object's shared fence list
445 * @obj: the reservation object
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
451 static inline struct dma_resv_list *dma_resv_shared_list(struct dma_resv *obj)
453 return rcu_dereference_check(obj->fence, dma_resv_held(obj));
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);
469 #endif /* _LINUX_RESERVATION_H */