1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Fence mechanism for dma-buf to allow for asynchronous dma access
4  *
5  * Copyright (C) 2012 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  */
12 
13 #ifndef __LINUX_DMA_FENCE_H
14 #define __LINUX_DMA_FENCE_H
15 
16 #include <linux/err.h>
17 #include <linux/wait.h>
18 #include <linux/list.h>
19 #include <linux/bitops.h>
20 #include <linux/kref.h>
21 #include <linux/sched.h>
22 #include <linux/printk.h>
23 #include <linux/rcupdate.h>
24 
25 struct dma_fence;
26 struct dma_fence_ops;
27 struct dma_fence_cb;
28 
29 /**
30  * struct dma_fence - software synchronization primitive
31  * @refcount: refcount for this fence
32  * @ops: dma_fence_ops associated with this fence
33  * @rcu: used for releasing fence with kfree_rcu
34  * @cb_list: list of all callbacks to call
35  * @lock: spin_lock_irqsave used for locking
36  * @context: execution context this fence belongs to, returned by
37  *           dma_fence_context_alloc()
38  * @seqno: the sequence number of this fence inside the execution context,
39  * can be compared to decide which fence would be signaled later.
40  * @flags: A mask of DMA_FENCE_FLAG_* defined below
41  * @timestamp: Timestamp when the fence was signaled.
42  * @error: Optional, only valid if < 0, must be set before calling
43  * dma_fence_signal, indicates that the fence has completed with an error.
44  *
45  * the flags member must be manipulated and read using the appropriate
46  * atomic ops (bit_*), so taking the spinlock will not be needed most
47  * of the time.
48  *
49  * DMA_FENCE_FLAG_SIGNALED_BIT - fence is already signaled
50  * DMA_FENCE_FLAG_TIMESTAMP_BIT - timestamp recorded for fence signaling
51  * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT - enable_signaling might have been called
52  * DMA_FENCE_FLAG_USER_BITS - start of the unused bits, can be used by the
53  * implementer of the fence for its own purposes. Can be used in different
54  * ways by different fence implementers, so do not rely on this.
55  *
56  * Since atomic bitops are used, this is not guaranteed to be the case.
57  * Particularly, if the bit was set, but dma_fence_signal was called right
58  * before this bit was set, it would have been able to set the
59  * DMA_FENCE_FLAG_SIGNALED_BIT, before enable_signaling was called.
60  * Adding a check for DMA_FENCE_FLAG_SIGNALED_BIT after setting
61  * DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT closes this race, and makes sure that
62  * after dma_fence_signal was called, any enable_signaling call will have either
63  * been completed, or never called at all.
64  */
65 struct dma_fence {
66 	spinlock_t *lock;
67 	const struct dma_fence_ops *ops;
68 	/*
69 	 * We clear the callback list on kref_put so that by the time we
70 	 * release the fence it is unused. No one should be adding to the
71 	 * cb_list that they don't themselves hold a reference for.
72 	 *
73 	 * The lifetime of the timestamp is similarly tied to both the
74 	 * rcu freelist and the cb_list. The timestamp is only set upon
75 	 * signaling while simultaneously notifying the cb_list. Ergo, we
76 	 * only use either the cb_list of timestamp. Upon destruction,
77 	 * neither are accessible, and so we can use the rcu. This means
78 	 * that the cb_list is *only* valid until the signal bit is set,
79 	 * and to read either you *must* hold a reference to the fence,
80 	 * and not just the rcu_read_lock.
81 	 *
82 	 * Listed in chronological order.
83 	 */
84 	union {
85 		struct list_head cb_list;
86 		/* @cb_list replaced by @timestamp on dma_fence_signal() */
87 		ktime_t timestamp;
88 		/* @timestamp replaced by @rcu on dma_fence_release() */
89 		struct rcu_head rcu;
90 	};
91 	u64 context;
92 	u64 seqno;
93 	unsigned long flags;
94 	struct kref refcount;
95 	int error;
96 };
97 
98 enum dma_fence_flag_bits {
99 	DMA_FENCE_FLAG_SIGNALED_BIT,
100 	DMA_FENCE_FLAG_TIMESTAMP_BIT,
101 	DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
102 	DMA_FENCE_FLAG_USER_BITS, /* must always be last member */
103 };
104 
105 typedef void (*dma_fence_func_t)(struct dma_fence *fence,
106 				 struct dma_fence_cb *cb);
107 
108 /**
109  * struct dma_fence_cb - callback for dma_fence_add_callback()
110  * @node: used by dma_fence_add_callback() to append this struct to fence::cb_list
111  * @func: dma_fence_func_t to call
112  *
113  * This struct will be initialized by dma_fence_add_callback(), additional
114  * data can be passed along by embedding dma_fence_cb in another struct.
115  */
116 struct dma_fence_cb {
117 	struct list_head node;
118 	dma_fence_func_t func;
119 };
120 
121 /**
122  * struct dma_fence_ops - operations implemented for fence
123  *
124  */
125 struct dma_fence_ops {
126 	/**
127 	 * @use_64bit_seqno:
128 	 *
129 	 * True if this dma_fence implementation uses 64bit seqno, false
130 	 * otherwise.
131 	 */
132 	bool use_64bit_seqno;
133 
134 	/**
135 	 * @get_driver_name:
136 	 *
137 	 * Returns the driver name. This is a callback to allow drivers to
138 	 * compute the name at runtime, without having it to store permanently
139 	 * for each fence, or build a cache of some sort.
140 	 *
141 	 * This callback is mandatory.
142 	 */
143 	const char * (*get_driver_name)(struct dma_fence *fence);
144 
145 	/**
146 	 * @get_timeline_name:
147 	 *
148 	 * Return the name of the context this fence belongs to. This is a
149 	 * callback to allow drivers to compute the name at runtime, without
150 	 * having it to store permanently for each fence, or build a cache of
151 	 * some sort.
152 	 *
153 	 * This callback is mandatory.
154 	 */
155 	const char * (*get_timeline_name)(struct dma_fence *fence);
156 
157 	/**
158 	 * @enable_signaling:
159 	 *
160 	 * Enable software signaling of fence.
161 	 *
162 	 * For fence implementations that have the capability for hw->hw
163 	 * signaling, they can implement this op to enable the necessary
164 	 * interrupts, or insert commands into cmdstream, etc, to avoid these
165 	 * costly operations for the common case where only hw->hw
166 	 * synchronization is required.  This is called in the first
167 	 * dma_fence_wait() or dma_fence_add_callback() path to let the fence
168 	 * implementation know that there is another driver waiting on the
169 	 * signal (ie. hw->sw case).
170 	 *
171 	 * This function can be called from atomic context, but not
172 	 * from irq context, so normal spinlocks can be used.
173 	 *
174 	 * A return value of false indicates the fence already passed,
175 	 * or some failure occurred that made it impossible to enable
176 	 * signaling. True indicates successful enabling.
177 	 *
178 	 * &dma_fence.error may be set in enable_signaling, but only when false
179 	 * is returned.
180 	 *
181 	 * Since many implementations can call dma_fence_signal() even when before
182 	 * @enable_signaling has been called there's a race window, where the
183 	 * dma_fence_signal() might result in the final fence reference being
184 	 * released and its memory freed. To avoid this, implementations of this
185 	 * callback should grab their own reference using dma_fence_get(), to be
186 	 * released when the fence is signalled (through e.g. the interrupt
187 	 * handler).
188 	 *
189 	 * This callback is optional. If this callback is not present, then the
190 	 * driver must always have signaling enabled.
191 	 */
192 	bool (*enable_signaling)(struct dma_fence *fence);
193 
194 	/**
195 	 * @signaled:
196 	 *
197 	 * Peek whether the fence is signaled, as a fastpath optimization for
198 	 * e.g. dma_fence_wait() or dma_fence_add_callback(). Note that this
199 	 * callback does not need to make any guarantees beyond that a fence
200 	 * once indicates as signalled must always return true from this
201 	 * callback. This callback may return false even if the fence has
202 	 * completed already, in this case information hasn't propogated throug
203 	 * the system yet. See also dma_fence_is_signaled().
204 	 *
205 	 * May set &dma_fence.error if returning true.
206 	 *
207 	 * This callback is optional.
208 	 */
209 	bool (*signaled)(struct dma_fence *fence);
210 
211 	/**
212 	 * @wait:
213 	 *
214 	 * Custom wait implementation, defaults to dma_fence_default_wait() if
215 	 * not set.
216 	 *
217 	 * Deprecated and should not be used by new implementations. Only used
218 	 * by existing implementations which need special handling for their
219 	 * hardware reset procedure.
220 	 *
221 	 * Must return -ERESTARTSYS if the wait is intr = true and the wait was
222 	 * interrupted, and remaining jiffies if fence has signaled, or 0 if wait
223 	 * timed out. Can also return other error values on custom implementations,
224 	 * which should be treated as if the fence is signaled. For example a hardware
225 	 * lockup could be reported like that.
226 	 */
227 	signed long (*wait)(struct dma_fence *fence,
228 			    bool intr, signed long timeout);
229 
230 	/**
231 	 * @release:
232 	 *
233 	 * Called on destruction of fence to release additional resources.
234 	 * Can be called from irq context.  This callback is optional. If it is
235 	 * NULL, then dma_fence_free() is instead called as the default
236 	 * implementation.
237 	 */
238 	void (*release)(struct dma_fence *fence);
239 
240 	/**
241 	 * @fence_value_str:
242 	 *
243 	 * Callback to fill in free-form debug info specific to this fence, like
244 	 * the sequence number.
245 	 *
246 	 * This callback is optional.
247 	 */
248 	void (*fence_value_str)(struct dma_fence *fence, char *str, int size);
249 
250 	/**
251 	 * @timeline_value_str:
252 	 *
253 	 * Fills in the current value of the timeline as a string, like the
254 	 * sequence number. Note that the specific fence passed to this function
255 	 * should not matter, drivers should only use it to look up the
256 	 * corresponding timeline structures.
257 	 */
258 	void (*timeline_value_str)(struct dma_fence *fence,
259 				   char *str, int size);
260 };
261 
262 void dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
263 		    spinlock_t *lock, u64 context, u64 seqno);
264 
265 void dma_fence_release(struct kref *kref);
266 void dma_fence_free(struct dma_fence *fence);
267 void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq);
268 
269 /**
270  * dma_fence_put - decreases refcount of the fence
271  * @fence: fence to reduce refcount of
272  */
dma_fence_put(struct dma_fence * fence)273 static inline void dma_fence_put(struct dma_fence *fence)
274 {
275 	if (fence)
276 		kref_put(&fence->refcount, dma_fence_release);
277 }
278 
279 /**
280  * dma_fence_get - increases refcount of the fence
281  * @fence: fence to increase refcount of
282  *
283  * Returns the same fence, with refcount increased by 1.
284  */
dma_fence_get(struct dma_fence * fence)285 static inline struct dma_fence *dma_fence_get(struct dma_fence *fence)
286 {
287 	if (fence)
288 		kref_get(&fence->refcount);
289 	return fence;
290 }
291 
292 /**
293  * dma_fence_get_rcu - get a fence from a dma_resv_list with
294  *                     rcu read lock
295  * @fence: fence to increase refcount of
296  *
297  * Function returns NULL if no refcount could be obtained, or the fence.
298  */
dma_fence_get_rcu(struct dma_fence * fence)299 static inline struct dma_fence *dma_fence_get_rcu(struct dma_fence *fence)
300 {
301 	if (kref_get_unless_zero(&fence->refcount))
302 		return fence;
303 	else
304 		return NULL;
305 }
306 
307 /**
308  * dma_fence_get_rcu_safe  - acquire a reference to an RCU tracked fence
309  * @fencep: pointer to fence to increase refcount of
310  *
311  * Function returns NULL if no refcount could be obtained, or the fence.
312  * This function handles acquiring a reference to a fence that may be
313  * reallocated within the RCU grace period (such as with SLAB_TYPESAFE_BY_RCU),
314  * so long as the caller is using RCU on the pointer to the fence.
315  *
316  * An alternative mechanism is to employ a seqlock to protect a bunch of
317  * fences, such as used by struct dma_resv. When using a seqlock,
318  * the seqlock must be taken before and checked after a reference to the
319  * fence is acquired (as shown here).
320  *
321  * The caller is required to hold the RCU read lock.
322  */
323 static inline struct dma_fence *
dma_fence_get_rcu_safe(struct dma_fence __rcu ** fencep)324 dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep)
325 {
326 	do {
327 		struct dma_fence *fence;
328 
329 		fence = rcu_dereference(*fencep);
330 		if (!fence)
331 			return NULL;
332 
333 		if (!dma_fence_get_rcu(fence))
334 			continue;
335 
336 		/* The atomic_inc_not_zero() inside dma_fence_get_rcu()
337 		 * provides a full memory barrier upon success (such as now).
338 		 * This is paired with the write barrier from assigning
339 		 * to the __rcu protected fence pointer so that if that
340 		 * pointer still matches the current fence, we know we
341 		 * have successfully acquire a reference to it. If it no
342 		 * longer matches, we are holding a reference to some other
343 		 * reallocated pointer. This is possible if the allocator
344 		 * is using a freelist like SLAB_TYPESAFE_BY_RCU where the
345 		 * fence remains valid for the RCU grace period, but it
346 		 * may be reallocated. When using such allocators, we are
347 		 * responsible for ensuring the reference we get is to
348 		 * the right fence, as below.
349 		 */
350 		if (fence == rcu_access_pointer(*fencep))
351 			return rcu_pointer_handoff(fence);
352 
353 		dma_fence_put(fence);
354 	} while (1);
355 }
356 
357 #ifdef CONFIG_LOCKDEP
358 bool dma_fence_begin_signalling(void);
359 void dma_fence_end_signalling(bool cookie);
360 void __dma_fence_might_wait(void);
361 #else
dma_fence_begin_signalling(void)362 static inline bool dma_fence_begin_signalling(void)
363 {
364 	return true;
365 }
dma_fence_end_signalling(bool cookie)366 static inline void dma_fence_end_signalling(bool cookie) {}
__dma_fence_might_wait(void)367 static inline void __dma_fence_might_wait(void) {}
368 #endif
369 
370 int dma_fence_signal(struct dma_fence *fence);
371 int dma_fence_signal_locked(struct dma_fence *fence);
372 int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp);
373 int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
374 				      ktime_t timestamp);
375 signed long dma_fence_default_wait(struct dma_fence *fence,
376 				   bool intr, signed long timeout);
377 int dma_fence_add_callback(struct dma_fence *fence,
378 			   struct dma_fence_cb *cb,
379 			   dma_fence_func_t func);
380 bool dma_fence_remove_callback(struct dma_fence *fence,
381 			       struct dma_fence_cb *cb);
382 void dma_fence_enable_sw_signaling(struct dma_fence *fence);
383 
384 /**
385  * dma_fence_is_signaled_locked - Return an indication if the fence
386  *                                is signaled yet.
387  * @fence: the fence to check
388  *
389  * Returns true if the fence was already signaled, false if not. Since this
390  * function doesn't enable signaling, it is not guaranteed to ever return
391  * true if dma_fence_add_callback(), dma_fence_wait() or
392  * dma_fence_enable_sw_signaling() haven't been called before.
393  *
394  * This function requires &dma_fence.lock to be held.
395  *
396  * See also dma_fence_is_signaled().
397  */
398 static inline bool
dma_fence_is_signaled_locked(struct dma_fence * fence)399 dma_fence_is_signaled_locked(struct dma_fence *fence)
400 {
401 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
402 		return true;
403 
404 	if (fence->ops->signaled && fence->ops->signaled(fence)) {
405 		dma_fence_signal_locked(fence);
406 		return true;
407 	}
408 
409 	return false;
410 }
411 
412 /**
413  * dma_fence_is_signaled - Return an indication if the fence is signaled yet.
414  * @fence: the fence to check
415  *
416  * Returns true if the fence was already signaled, false if not. Since this
417  * function doesn't enable signaling, it is not guaranteed to ever return
418  * true if dma_fence_add_callback(), dma_fence_wait() or
419  * dma_fence_enable_sw_signaling() haven't been called before.
420  *
421  * It's recommended for seqno fences to call dma_fence_signal when the
422  * operation is complete, it makes it possible to prevent issues from
423  * wraparound between time of issue and time of use by checking the return
424  * value of this function before calling hardware-specific wait instructions.
425  *
426  * See also dma_fence_is_signaled_locked().
427  */
428 static inline bool
dma_fence_is_signaled(struct dma_fence * fence)429 dma_fence_is_signaled(struct dma_fence *fence)
430 {
431 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
432 		return true;
433 
434 	if (fence->ops->signaled && fence->ops->signaled(fence)) {
435 		dma_fence_signal(fence);
436 		return true;
437 	}
438 
439 	return false;
440 }
441 
442 /**
443  * __dma_fence_is_later - return if f1 is chronologically later than f2
444  * @f1: the first fence's seqno
445  * @f2: the second fence's seqno from the same context
446  * @ops: dma_fence_ops associated with the seqno
447  *
448  * Returns true if f1 is chronologically later than f2. Both fences must be
449  * from the same context, since a seqno is not common across contexts.
450  */
__dma_fence_is_later(u64 f1,u64 f2,const struct dma_fence_ops * ops)451 static inline bool __dma_fence_is_later(u64 f1, u64 f2,
452 					const struct dma_fence_ops *ops)
453 {
454 	/* This is for backward compatibility with drivers which can only handle
455 	 * 32bit sequence numbers. Use a 64bit compare when the driver says to
456 	 * do so.
457 	 */
458 	if (ops->use_64bit_seqno)
459 		return f1 > f2;
460 
461 	return (int)(lower_32_bits(f1) - lower_32_bits(f2)) > 0;
462 }
463 
464 /**
465  * dma_fence_is_later - return if f1 is chronologically later than f2
466  * @f1: the first fence from the same context
467  * @f2: the second fence from the same context
468  *
469  * Returns true if f1 is chronologically later than f2. Both fences must be
470  * from the same context, since a seqno is not re-used across contexts.
471  */
dma_fence_is_later(struct dma_fence * f1,struct dma_fence * f2)472 static inline bool dma_fence_is_later(struct dma_fence *f1,
473 				      struct dma_fence *f2)
474 {
475 	if (WARN_ON(f1->context != f2->context))
476 		return false;
477 
478 	return __dma_fence_is_later(f1->seqno, f2->seqno, f1->ops);
479 }
480 
481 /**
482  * dma_fence_later - return the chronologically later fence
483  * @f1:	the first fence from the same context
484  * @f2:	the second fence from the same context
485  *
486  * Returns NULL if both fences are signaled, otherwise the fence that would be
487  * signaled last. Both fences must be from the same context, since a seqno is
488  * not re-used across contexts.
489  */
dma_fence_later(struct dma_fence * f1,struct dma_fence * f2)490 static inline struct dma_fence *dma_fence_later(struct dma_fence *f1,
491 						struct dma_fence *f2)
492 {
493 	if (WARN_ON(f1->context != f2->context))
494 		return NULL;
495 
496 	/*
497 	 * Can't check just DMA_FENCE_FLAG_SIGNALED_BIT here, it may never
498 	 * have been set if enable_signaling wasn't called, and enabling that
499 	 * here is overkill.
500 	 */
501 	if (dma_fence_is_later(f1, f2))
502 		return dma_fence_is_signaled(f1) ? NULL : f1;
503 	else
504 		return dma_fence_is_signaled(f2) ? NULL : f2;
505 }
506 
507 /**
508  * dma_fence_get_status_locked - returns the status upon completion
509  * @fence: the dma_fence to query
510  *
511  * Drivers can supply an optional error status condition before they signal
512  * the fence (to indicate whether the fence was completed due to an error
513  * rather than success). The value of the status condition is only valid
514  * if the fence has been signaled, dma_fence_get_status_locked() first checks
515  * the signal state before reporting the error status.
516  *
517  * Returns 0 if the fence has not yet been signaled, 1 if the fence has
518  * been signaled without an error condition, or a negative error code
519  * if the fence has been completed in err.
520  */
dma_fence_get_status_locked(struct dma_fence * fence)521 static inline int dma_fence_get_status_locked(struct dma_fence *fence)
522 {
523 	if (dma_fence_is_signaled_locked(fence))
524 		return fence->error ?: 1;
525 	else
526 		return 0;
527 }
528 
529 int dma_fence_get_status(struct dma_fence *fence);
530 
531 /**
532  * dma_fence_set_error - flag an error condition on the fence
533  * @fence: the dma_fence
534  * @error: the error to store
535  *
536  * Drivers can supply an optional error status condition before they signal
537  * the fence, to indicate that the fence was completed due to an error
538  * rather than success. This must be set before signaling (so that the value
539  * is visible before any waiters on the signal callback are woken). This
540  * helper exists to help catching erroneous setting of #dma_fence.error.
541  */
dma_fence_set_error(struct dma_fence * fence,int error)542 static inline void dma_fence_set_error(struct dma_fence *fence,
543 				       int error)
544 {
545 	WARN_ON(test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags));
546 	WARN_ON(error >= 0 || error < -MAX_ERRNO);
547 
548 	fence->error = error;
549 }
550 
551 signed long dma_fence_wait_timeout(struct dma_fence *,
552 				   bool intr, signed long timeout);
553 signed long dma_fence_wait_any_timeout(struct dma_fence **fences,
554 				       uint32_t count,
555 				       bool intr, signed long timeout,
556 				       uint32_t *idx);
557 
558 /**
559  * dma_fence_wait - sleep until the fence gets signaled
560  * @fence: the fence to wait on
561  * @intr: if true, do an interruptible wait
562  *
563  * This function will return -ERESTARTSYS if interrupted by a signal,
564  * or 0 if the fence was signaled. Other error values may be
565  * returned on custom implementations.
566  *
567  * Performs a synchronous wait on this fence. It is assumed the caller
568  * directly or indirectly holds a reference to the fence, otherwise the
569  * fence might be freed before return, resulting in undefined behavior.
570  *
571  * See also dma_fence_wait_timeout() and dma_fence_wait_any_timeout().
572  */
dma_fence_wait(struct dma_fence * fence,bool intr)573 static inline signed long dma_fence_wait(struct dma_fence *fence, bool intr)
574 {
575 	signed long ret;
576 
577 	/* Since dma_fence_wait_timeout cannot timeout with
578 	 * MAX_SCHEDULE_TIMEOUT, only valid return values are
579 	 * -ERESTARTSYS and MAX_SCHEDULE_TIMEOUT.
580 	 */
581 	ret = dma_fence_wait_timeout(fence, intr, MAX_SCHEDULE_TIMEOUT);
582 
583 	return ret < 0 ? ret : 0;
584 }
585 
586 struct dma_fence *dma_fence_get_stub(void);
587 struct dma_fence *dma_fence_allocate_private_stub(void);
588 u64 dma_fence_context_alloc(unsigned num);
589 
590 extern const struct dma_fence_ops dma_fence_array_ops;
591 extern const struct dma_fence_ops dma_fence_chain_ops;
592 
593 /**
594  * dma_fence_is_array - check if a fence is from the array subclass
595  * @fence: the fence to test
596  *
597  * Return true if it is a dma_fence_array and false otherwise.
598  */
dma_fence_is_array(struct dma_fence * fence)599 static inline bool dma_fence_is_array(struct dma_fence *fence)
600 {
601 	return fence->ops == &dma_fence_array_ops;
602 }
603 
604 /**
605  * dma_fence_is_chain - check if a fence is from the chain subclass
606  * @fence: the fence to test
607  *
608  * Return true if it is a dma_fence_chain and false otherwise.
609  */
dma_fence_is_chain(struct dma_fence * fence)610 static inline bool dma_fence_is_chain(struct dma_fence *fence)
611 {
612 	return fence->ops == &dma_fence_chain_ops;
613 }
614 
615 /**
616  * dma_fence_is_container - check if a fence is a container for other fences
617  * @fence: the fence to test
618  *
619  * Return true if this fence is a container for other fences, false otherwise.
620  * This is important since we can't build up large fence structure or otherwise
621  * we run into recursion during operation on those fences.
622  */
dma_fence_is_container(struct dma_fence * fence)623 static inline bool dma_fence_is_container(struct dma_fence *fence)
624 {
625 	return dma_fence_is_array(fence) || dma_fence_is_chain(fence);
626 }
627 
628 #endif /* __LINUX_DMA_FENCE_H */
629