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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Fence mechanism for dma-buf and 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#include <linux/slab.h>
14#include <linux/export.h>
15#include <linux/atomic.h>
16#include <linux/dma-fence.h>
17#include <linux/sched/signal.h>
18#include <linux/seq_file.h>
19
20#define CREATE_TRACE_POINTS
21#include <trace/events/dma_fence.h>
22
23EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
24EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
25EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
26
27static DEFINE_SPINLOCK(dma_fence_stub_lock);
28static struct dma_fence dma_fence_stub;
29
30/*
31 * fence context counter: each execution context should have its own
32 * fence context, this allows checking if fences belong to the same
33 * context or not. One device can have multiple separate contexts,
34 * and they're used if some engine can run independently of another.
35 */
36static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(1);
37
38/**
39 * DOC: DMA fences overview
40 *
41 * DMA fences, represented by &struct dma_fence, are the kernel internal
42 * synchronization primitive for DMA operations like GPU rendering, video
43 * encoding/decoding, or displaying buffers on a screen.
44 *
45 * A fence is initialized using dma_fence_init() and completed using
46 * dma_fence_signal(). Fences are associated with a context, allocated through
47 * dma_fence_context_alloc(), and all fences on the same context are
48 * fully ordered.
49 *
50 * Since the purposes of fences is to facilitate cross-device and
51 * cross-application synchronization, there's multiple ways to use one:
52 *
53 * - Individual fences can be exposed as a &sync_file, accessed as a file
54 * descriptor from userspace, created by calling sync_file_create(). This is
55 * called explicit fencing, since userspace passes around explicit
56 * synchronization points.
57 *
58 * - Some subsystems also have their own explicit fencing primitives, like
59 * &drm_syncobj. Compared to &sync_file, a &drm_syncobj allows the underlying
60 * fence to be updated.
61 *
62 * - Then there's also implicit fencing, where the synchronization points are
63 * implicitly passed around as part of shared &dma_buf instances. Such
64 * implicit fences are stored in &struct dma_resv through the
65 * &dma_buf.resv pointer.
66 */
67
68/**
69 * DOC: fence cross-driver contract
70 *
71 * Since &dma_fence provide a cross driver contract, all drivers must follow the
72 * same rules:
73 *
74 * * Fences must complete in a reasonable time. Fences which represent kernels
75 * and shaders submitted by userspace, which could run forever, must be backed
76 * up by timeout and gpu hang recovery code. Minimally that code must prevent
77 * further command submission and force complete all in-flight fences, e.g.
78 * when the driver or hardware do not support gpu reset, or if the gpu reset
79 * failed for some reason. Ideally the driver supports gpu recovery which only
80 * affects the offending userspace context, and no other userspace
81 * submissions.
82 *
83 * * Drivers may have different ideas of what completion within a reasonable
84 * time means. Some hang recovery code uses a fixed timeout, others a mix
85 * between observing forward progress and increasingly strict timeouts.
86 * Drivers should not try to second guess timeout handling of fences from
87 * other drivers.
88 *
89 * * To ensure there's no deadlocks of dma_fence_wait() against other locks
90 * drivers should annotate all code required to reach dma_fence_signal(),
91 * which completes the fences, with dma_fence_begin_signalling() and
92 * dma_fence_end_signalling().
93 *
94 * * Drivers are allowed to call dma_fence_wait() while holding dma_resv_lock().
95 * This means any code required for fence completion cannot acquire a
96 * &dma_resv lock. Note that this also pulls in the entire established
97 * locking hierarchy around dma_resv_lock() and dma_resv_unlock().
98 *
99 * * Drivers are allowed to call dma_fence_wait() from their &shrinker
100 * callbacks. This means any code required for fence completion cannot
101 * allocate memory with GFP_KERNEL.
102 *
103 * * Drivers are allowed to call dma_fence_wait() from their &mmu_notifier
104 * respectively &mmu_interval_notifier callbacks. This means any code required
105 * for fence completeion cannot allocate memory with GFP_NOFS or GFP_NOIO.
106 * Only GFP_ATOMIC is permissible, which might fail.
107 *
108 * Note that only GPU drivers have a reasonable excuse for both requiring
109 * &mmu_interval_notifier and &shrinker callbacks at the same time as having to
110 * track asynchronous compute work using &dma_fence. No driver outside of
111 * drivers/gpu should ever call dma_fence_wait() in such contexts.
112 */
113
114static const char *dma_fence_stub_get_name(struct dma_fence *fence)
115{
116 return "stub";
117}
118
119static const struct dma_fence_ops dma_fence_stub_ops = {
120 .get_driver_name = dma_fence_stub_get_name,
121 .get_timeline_name = dma_fence_stub_get_name,
122};
123
124/**
125 * dma_fence_get_stub - return a signaled fence
126 *
127 * Return a stub fence which is already signaled. The fence's
128 * timestamp corresponds to the first time after boot this
129 * function is called.
130 */
131struct dma_fence *dma_fence_get_stub(void)
132{
133 spin_lock(&dma_fence_stub_lock);
134 if (!dma_fence_stub.ops) {
135 dma_fence_init(&dma_fence_stub,
136 &dma_fence_stub_ops,
137 &dma_fence_stub_lock,
138 0, 0);
139
140 set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
141 &dma_fence_stub.flags);
142
143 dma_fence_signal_locked(&dma_fence_stub);
144 }
145 spin_unlock(&dma_fence_stub_lock);
146
147 return dma_fence_get(&dma_fence_stub);
148}
149EXPORT_SYMBOL(dma_fence_get_stub);
150
151/**
152 * dma_fence_allocate_private_stub - return a private, signaled fence
153 * @timestamp: timestamp when the fence was signaled
154 *
155 * Return a newly allocated and signaled stub fence.
156 */
157struct dma_fence *dma_fence_allocate_private_stub(ktime_t timestamp)
158{
159 struct dma_fence *fence;
160
161 fence = kzalloc(sizeof(*fence), GFP_KERNEL);
162 if (fence == NULL)
163 return NULL;
164
165 dma_fence_init(fence,
166 &dma_fence_stub_ops,
167 &dma_fence_stub_lock,
168 0, 0);
169
170 set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
171 &fence->flags);
172
173 dma_fence_signal_timestamp(fence, timestamp);
174
175 return fence;
176}
177EXPORT_SYMBOL(dma_fence_allocate_private_stub);
178
179/**
180 * dma_fence_context_alloc - allocate an array of fence contexts
181 * @num: amount of contexts to allocate
182 *
183 * This function will return the first index of the number of fence contexts
184 * allocated. The fence context is used for setting &dma_fence.context to a
185 * unique number by passing the context to dma_fence_init().
186 */
187u64 dma_fence_context_alloc(unsigned num)
188{
189 WARN_ON(!num);
190 return atomic64_fetch_add(num, &dma_fence_context_counter);
191}
192EXPORT_SYMBOL(dma_fence_context_alloc);
193
194/**
195 * DOC: fence signalling annotation
196 *
197 * Proving correctness of all the kernel code around &dma_fence through code
198 * review and testing is tricky for a few reasons:
199 *
200 * * It is a cross-driver contract, and therefore all drivers must follow the
201 * same rules for lock nesting order, calling contexts for various functions
202 * and anything else significant for in-kernel interfaces. But it is also
203 * impossible to test all drivers in a single machine, hence brute-force N vs.
204 * N testing of all combinations is impossible. Even just limiting to the
205 * possible combinations is infeasible.
206 *
207 * * There is an enormous amount of driver code involved. For render drivers
208 * there's the tail of command submission, after fences are published,
209 * scheduler code, interrupt and workers to process job completion,
210 * and timeout, gpu reset and gpu hang recovery code. Plus for integration
211 * with core mm with have &mmu_notifier, respectively &mmu_interval_notifier,
212 * and &shrinker. For modesetting drivers there's the commit tail functions
213 * between when fences for an atomic modeset are published, and when the
214 * corresponding vblank completes, including any interrupt processing and
215 * related workers. Auditing all that code, across all drivers, is not
216 * feasible.
217 *
218 * * Due to how many other subsystems are involved and the locking hierarchies
219 * this pulls in there is extremely thin wiggle-room for driver-specific
220 * differences. &dma_fence interacts with almost all of the core memory
221 * handling through page fault handlers via &dma_resv, dma_resv_lock() and
222 * dma_resv_unlock(). On the other side it also interacts through all
223 * allocation sites through &mmu_notifier and &shrinker.
224 *
225 * Furthermore lockdep does not handle cross-release dependencies, which means
226 * any deadlocks between dma_fence_wait() and dma_fence_signal() can't be caught
227 * at runtime with some quick testing. The simplest example is one thread
228 * waiting on a &dma_fence while holding a lock::
229 *
230 * lock(A);
231 * dma_fence_wait(B);
232 * unlock(A);
233 *
234 * while the other thread is stuck trying to acquire the same lock, which
235 * prevents it from signalling the fence the previous thread is stuck waiting
236 * on::
237 *
238 * lock(A);
239 * unlock(A);
240 * dma_fence_signal(B);
241 *
242 * By manually annotating all code relevant to signalling a &dma_fence we can
243 * teach lockdep about these dependencies, which also helps with the validation
244 * headache since now lockdep can check all the rules for us::
245 *
246 * cookie = dma_fence_begin_signalling();
247 * lock(A);
248 * unlock(A);
249 * dma_fence_signal(B);
250 * dma_fence_end_signalling(cookie);
251 *
252 * For using dma_fence_begin_signalling() and dma_fence_end_signalling() to
253 * annotate critical sections the following rules need to be observed:
254 *
255 * * All code necessary to complete a &dma_fence must be annotated, from the
256 * point where a fence is accessible to other threads, to the point where
257 * dma_fence_signal() is called. Un-annotated code can contain deadlock issues,
258 * and due to the very strict rules and many corner cases it is infeasible to
259 * catch these just with review or normal stress testing.
260 *
261 * * &struct dma_resv deserves a special note, since the readers are only
262 * protected by rcu. This means the signalling critical section starts as soon
263 * as the new fences are installed, even before dma_resv_unlock() is called.
264 *
265 * * The only exception are fast paths and opportunistic signalling code, which
266 * calls dma_fence_signal() purely as an optimization, but is not required to
267 * guarantee completion of a &dma_fence. The usual example is a wait IOCTL
268 * which calls dma_fence_signal(), while the mandatory completion path goes
269 * through a hardware interrupt and possible job completion worker.
270 *
271 * * To aid composability of code, the annotations can be freely nested, as long
272 * as the overall locking hierarchy is consistent. The annotations also work
273 * both in interrupt and process context. Due to implementation details this
274 * requires that callers pass an opaque cookie from
275 * dma_fence_begin_signalling() to dma_fence_end_signalling().
276 *
277 * * Validation against the cross driver contract is implemented by priming
278 * lockdep with the relevant hierarchy at boot-up. This means even just
279 * testing with a single device is enough to validate a driver, at least as
280 * far as deadlocks with dma_fence_wait() against dma_fence_signal() are
281 * concerned.
282 */
283#ifdef CONFIG_LOCKDEP
284static struct lockdep_map dma_fence_lockdep_map = {
285 .name = "dma_fence_map"
286};
287
288/**
289 * dma_fence_begin_signalling - begin a critical DMA fence signalling section
290 *
291 * Drivers should use this to annotate the beginning of any code section
292 * required to eventually complete &dma_fence by calling dma_fence_signal().
293 *
294 * The end of these critical sections are annotated with
295 * dma_fence_end_signalling().
296 *
297 * Returns:
298 *
299 * Opaque cookie needed by the implementation, which needs to be passed to
300 * dma_fence_end_signalling().
301 */
302bool dma_fence_begin_signalling(void)
303{
304 /* explicitly nesting ... */
305 if (lock_is_held_type(&dma_fence_lockdep_map, 1))
306 return true;
307
308 /* rely on might_sleep check for soft/hardirq locks */
309 if (in_atomic())
310 return true;
311
312 /* ... and non-recursive readlock */
313 lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _RET_IP_);
314
315 return false;
316}
317EXPORT_SYMBOL(dma_fence_begin_signalling);
318
319/**
320 * dma_fence_end_signalling - end a critical DMA fence signalling section
321 * @cookie: opaque cookie from dma_fence_begin_signalling()
322 *
323 * Closes a critical section annotation opened by dma_fence_begin_signalling().
324 */
325void dma_fence_end_signalling(bool cookie)
326{
327 if (cookie)
328 return;
329
330 lock_release(&dma_fence_lockdep_map, _RET_IP_);
331}
332EXPORT_SYMBOL(dma_fence_end_signalling);
333
334void __dma_fence_might_wait(void)
335{
336 bool tmp;
337
338 tmp = lock_is_held_type(&dma_fence_lockdep_map, 1);
339 if (tmp)
340 lock_release(&dma_fence_lockdep_map, _THIS_IP_);
341 lock_map_acquire(&dma_fence_lockdep_map);
342 lock_map_release(&dma_fence_lockdep_map);
343 if (tmp)
344 lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _THIS_IP_);
345}
346#endif
347
348
349/**
350 * dma_fence_signal_timestamp_locked - signal completion of a fence
351 * @fence: the fence to signal
352 * @timestamp: fence signal timestamp in kernel's CLOCK_MONOTONIC time domain
353 *
354 * Signal completion for software callbacks on a fence, this will unblock
355 * dma_fence_wait() calls and run all the callbacks added with
356 * dma_fence_add_callback(). Can be called multiple times, but since a fence
357 * can only go from the unsignaled to the signaled state and not back, it will
358 * only be effective the first time. Set the timestamp provided as the fence
359 * signal timestamp.
360 *
361 * Unlike dma_fence_signal_timestamp(), this function must be called with
362 * &dma_fence.lock held.
363 *
364 * Returns 0 on success and a negative error value when @fence has been
365 * signalled already.
366 */
367int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
368 ktime_t timestamp)
369{
370 struct dma_fence_cb *cur, *tmp;
371 struct list_head cb_list;
372
373 lockdep_assert_held(fence->lock);
374
375 if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
376 &fence->flags)))
377 return -EINVAL;
378
379 /* Stash the cb_list before replacing it with the timestamp */
380 list_replace(&fence->cb_list, &cb_list);
381
382 fence->timestamp = timestamp;
383 set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
384 trace_dma_fence_signaled(fence);
385
386 list_for_each_entry_safe(cur, tmp, &cb_list, node) {
387 INIT_LIST_HEAD(&cur->node);
388 cur->func(fence, cur);
389 }
390
391 return 0;
392}
393EXPORT_SYMBOL(dma_fence_signal_timestamp_locked);
394
395/**
396 * dma_fence_signal_timestamp - signal completion of a fence
397 * @fence: the fence to signal
398 * @timestamp: fence signal timestamp in kernel's CLOCK_MONOTONIC time domain
399 *
400 * Signal completion for software callbacks on a fence, this will unblock
401 * dma_fence_wait() calls and run all the callbacks added with
402 * dma_fence_add_callback(). Can be called multiple times, but since a fence
403 * can only go from the unsignaled to the signaled state and not back, it will
404 * only be effective the first time. Set the timestamp provided as the fence
405 * signal timestamp.
406 *
407 * Returns 0 on success and a negative error value when @fence has been
408 * signalled already.
409 */
410int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp)
411{
412 unsigned long flags;
413 int ret;
414
415 if (!fence)
416 return -EINVAL;
417
418 spin_lock_irqsave(fence->lock, flags);
419 ret = dma_fence_signal_timestamp_locked(fence, timestamp);
420 spin_unlock_irqrestore(fence->lock, flags);
421
422 return ret;
423}
424EXPORT_SYMBOL(dma_fence_signal_timestamp);
425
426/**
427 * dma_fence_signal_locked - signal completion of a fence
428 * @fence: the fence to signal
429 *
430 * Signal completion for software callbacks on a fence, this will unblock
431 * dma_fence_wait() calls and run all the callbacks added with
432 * dma_fence_add_callback(). Can be called multiple times, but since a fence
433 * can only go from the unsignaled to the signaled state and not back, it will
434 * only be effective the first time.
435 *
436 * Unlike dma_fence_signal(), this function must be called with &dma_fence.lock
437 * held.
438 *
439 * Returns 0 on success and a negative error value when @fence has been
440 * signalled already.
441 */
442int dma_fence_signal_locked(struct dma_fence *fence)
443{
444 return dma_fence_signal_timestamp_locked(fence, ktime_get());
445}
446EXPORT_SYMBOL(dma_fence_signal_locked);
447
448/**
449 * dma_fence_signal - signal completion of a fence
450 * @fence: the fence to signal
451 *
452 * Signal completion for software callbacks on a fence, this will unblock
453 * dma_fence_wait() calls and run all the callbacks added with
454 * dma_fence_add_callback(). Can be called multiple times, but since a fence
455 * can only go from the unsignaled to the signaled state and not back, it will
456 * only be effective the first time.
457 *
458 * Returns 0 on success and a negative error value when @fence has been
459 * signalled already.
460 */
461int dma_fence_signal(struct dma_fence *fence)
462{
463 unsigned long flags;
464 int ret;
465 bool tmp;
466
467 if (!fence)
468 return -EINVAL;
469
470 tmp = dma_fence_begin_signalling();
471
472 spin_lock_irqsave(fence->lock, flags);
473 ret = dma_fence_signal_timestamp_locked(fence, ktime_get());
474 spin_unlock_irqrestore(fence->lock, flags);
475
476 dma_fence_end_signalling(tmp);
477
478 return ret;
479}
480EXPORT_SYMBOL(dma_fence_signal);
481
482/**
483 * dma_fence_wait_timeout - sleep until the fence gets signaled
484 * or until timeout elapses
485 * @fence: the fence to wait on
486 * @intr: if true, do an interruptible wait
487 * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
488 *
489 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
490 * remaining timeout in jiffies on success. Other error values may be
491 * returned on custom implementations.
492 *
493 * Performs a synchronous wait on this fence. It is assumed the caller
494 * directly or indirectly (buf-mgr between reservation and committing)
495 * holds a reference to the fence, otherwise the fence might be
496 * freed before return, resulting in undefined behavior.
497 *
498 * See also dma_fence_wait() and dma_fence_wait_any_timeout().
499 */
500signed long
501dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
502{
503 signed long ret;
504
505 if (WARN_ON(timeout < 0))
506 return -EINVAL;
507
508 might_sleep();
509
510 __dma_fence_might_wait();
511
512 dma_fence_enable_sw_signaling(fence);
513
514 trace_dma_fence_wait_start(fence);
515 if (fence->ops->wait)
516 ret = fence->ops->wait(fence, intr, timeout);
517 else
518 ret = dma_fence_default_wait(fence, intr, timeout);
519 trace_dma_fence_wait_end(fence);
520 return ret;
521}
522EXPORT_SYMBOL(dma_fence_wait_timeout);
523
524/**
525 * dma_fence_release - default relese function for fences
526 * @kref: &dma_fence.recfount
527 *
528 * This is the default release functions for &dma_fence. Drivers shouldn't call
529 * this directly, but instead call dma_fence_put().
530 */
531void dma_fence_release(struct kref *kref)
532{
533 struct dma_fence *fence =
534 container_of(kref, struct dma_fence, refcount);
535
536 trace_dma_fence_destroy(fence);
537
538 if (WARN(!list_empty(&fence->cb_list) &&
539 !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags),
540 "Fence %s:%s:%llx:%llx released with pending signals!\n",
541 fence->ops->get_driver_name(fence),
542 fence->ops->get_timeline_name(fence),
543 fence->context, fence->seqno)) {
544 unsigned long flags;
545
546 /*
547 * Failed to signal before release, likely a refcounting issue.
548 *
549 * This should never happen, but if it does make sure that we
550 * don't leave chains dangling. We set the error flag first
551 * so that the callbacks know this signal is due to an error.
552 */
553 spin_lock_irqsave(fence->lock, flags);
554 fence->error = -EDEADLK;
555 dma_fence_signal_locked(fence);
556 spin_unlock_irqrestore(fence->lock, flags);
557 }
558
559 if (fence->ops->release)
560 fence->ops->release(fence);
561 else
562 dma_fence_free(fence);
563}
564EXPORT_SYMBOL(dma_fence_release);
565
566/**
567 * dma_fence_free - default release function for &dma_fence.
568 * @fence: fence to release
569 *
570 * This is the default implementation for &dma_fence_ops.release. It calls
571 * kfree_rcu() on @fence.
572 */
573void dma_fence_free(struct dma_fence *fence)
574{
575 kfree_rcu(fence, rcu);
576}
577EXPORT_SYMBOL(dma_fence_free);
578
579static bool __dma_fence_enable_signaling(struct dma_fence *fence)
580{
581 bool was_set;
582
583 lockdep_assert_held(fence->lock);
584
585 was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
586 &fence->flags);
587
588 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
589 return false;
590
591 if (!was_set && fence->ops->enable_signaling) {
592 trace_dma_fence_enable_signal(fence);
593
594 if (!fence->ops->enable_signaling(fence)) {
595 dma_fence_signal_locked(fence);
596 return false;
597 }
598 }
599
600 return true;
601}
602
603/**
604 * dma_fence_enable_sw_signaling - enable signaling on fence
605 * @fence: the fence to enable
606 *
607 * This will request for sw signaling to be enabled, to make the fence
608 * complete as soon as possible. This calls &dma_fence_ops.enable_signaling
609 * internally.
610 */
611void dma_fence_enable_sw_signaling(struct dma_fence *fence)
612{
613 unsigned long flags;
614
615 spin_lock_irqsave(fence->lock, flags);
616 __dma_fence_enable_signaling(fence);
617 spin_unlock_irqrestore(fence->lock, flags);
618}
619EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
620
621/**
622 * dma_fence_add_callback - add a callback to be called when the fence
623 * is signaled
624 * @fence: the fence to wait on
625 * @cb: the callback to register
626 * @func: the function to call
627 *
628 * Add a software callback to the fence. The caller should keep a reference to
629 * the fence.
630 *
631 * @cb will be initialized by dma_fence_add_callback(), no initialization
632 * by the caller is required. Any number of callbacks can be registered
633 * to a fence, but a callback can only be registered to one fence at a time.
634 *
635 * If fence is already signaled, this function will return -ENOENT (and
636 * *not* call the callback).
637 *
638 * Note that the callback can be called from an atomic context or irq context.
639 *
640 * Returns 0 in case of success, -ENOENT if the fence is already signaled
641 * and -EINVAL in case of error.
642 */
643int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
644 dma_fence_func_t func)
645{
646 unsigned long flags;
647 int ret = 0;
648
649 if (WARN_ON(!fence || !func))
650 return -EINVAL;
651
652 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
653 INIT_LIST_HEAD(&cb->node);
654 return -ENOENT;
655 }
656
657 spin_lock_irqsave(fence->lock, flags);
658
659 if (__dma_fence_enable_signaling(fence)) {
660 cb->func = func;
661 list_add_tail(&cb->node, &fence->cb_list);
662 } else {
663 INIT_LIST_HEAD(&cb->node);
664 ret = -ENOENT;
665 }
666
667 spin_unlock_irqrestore(fence->lock, flags);
668
669 return ret;
670}
671EXPORT_SYMBOL(dma_fence_add_callback);
672
673/**
674 * dma_fence_get_status - returns the status upon completion
675 * @fence: the dma_fence to query
676 *
677 * This wraps dma_fence_get_status_locked() to return the error status
678 * condition on a signaled fence. See dma_fence_get_status_locked() for more
679 * details.
680 *
681 * Returns 0 if the fence has not yet been signaled, 1 if the fence has
682 * been signaled without an error condition, or a negative error code
683 * if the fence has been completed in err.
684 */
685int dma_fence_get_status(struct dma_fence *fence)
686{
687 unsigned long flags;
688 int status;
689
690 spin_lock_irqsave(fence->lock, flags);
691 status = dma_fence_get_status_locked(fence);
692 spin_unlock_irqrestore(fence->lock, flags);
693
694 return status;
695}
696EXPORT_SYMBOL(dma_fence_get_status);
697
698/**
699 * dma_fence_remove_callback - remove a callback from the signaling list
700 * @fence: the fence to wait on
701 * @cb: the callback to remove
702 *
703 * Remove a previously queued callback from the fence. This function returns
704 * true if the callback is successfully removed, or false if the fence has
705 * already been signaled.
706 *
707 * *WARNING*:
708 * Cancelling a callback should only be done if you really know what you're
709 * doing, since deadlocks and race conditions could occur all too easily. For
710 * this reason, it should only ever be done on hardware lockup recovery,
711 * with a reference held to the fence.
712 *
713 * Behaviour is undefined if @cb has not been added to @fence using
714 * dma_fence_add_callback() beforehand.
715 */
716bool
717dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb)
718{
719 unsigned long flags;
720 bool ret;
721
722 spin_lock_irqsave(fence->lock, flags);
723
724 ret = !list_empty(&cb->node);
725 if (ret)
726 list_del_init(&cb->node);
727
728 spin_unlock_irqrestore(fence->lock, flags);
729
730 return ret;
731}
732EXPORT_SYMBOL(dma_fence_remove_callback);
733
734struct default_wait_cb {
735 struct dma_fence_cb base;
736 struct task_struct *task;
737};
738
739static void
740dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
741{
742 struct default_wait_cb *wait =
743 container_of(cb, struct default_wait_cb, base);
744
745 wake_up_state(wait->task, TASK_NORMAL);
746}
747
748/**
749 * dma_fence_default_wait - default sleep until the fence gets signaled
750 * or until timeout elapses
751 * @fence: the fence to wait on
752 * @intr: if true, do an interruptible wait
753 * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
754 *
755 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
756 * remaining timeout in jiffies on success. If timeout is zero the value one is
757 * returned if the fence is already signaled for consistency with other
758 * functions taking a jiffies timeout.
759 */
760signed long
761dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
762{
763 struct default_wait_cb cb;
764 unsigned long flags;
765 signed long ret = timeout ? timeout : 1;
766
767 spin_lock_irqsave(fence->lock, flags);
768
769 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
770 goto out;
771
772 if (intr && signal_pending(current)) {
773 ret = -ERESTARTSYS;
774 goto out;
775 }
776
777 if (!timeout) {
778 ret = 0;
779 goto out;
780 }
781
782 cb.base.func = dma_fence_default_wait_cb;
783 cb.task = current;
784 list_add(&cb.base.node, &fence->cb_list);
785
786 while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
787 if (intr)
788 __set_current_state(TASK_INTERRUPTIBLE);
789 else
790 __set_current_state(TASK_UNINTERRUPTIBLE);
791 spin_unlock_irqrestore(fence->lock, flags);
792
793 ret = schedule_timeout(ret);
794
795 spin_lock_irqsave(fence->lock, flags);
796 if (ret > 0 && intr && signal_pending(current))
797 ret = -ERESTARTSYS;
798 }
799
800 if (!list_empty(&cb.base.node))
801 list_del(&cb.base.node);
802 __set_current_state(TASK_RUNNING);
803
804out:
805 spin_unlock_irqrestore(fence->lock, flags);
806 return ret;
807}
808EXPORT_SYMBOL(dma_fence_default_wait);
809
810static bool
811dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count,
812 uint32_t *idx)
813{
814 int i;
815
816 for (i = 0; i < count; ++i) {
817 struct dma_fence *fence = fences[i];
818 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
819 if (idx)
820 *idx = i;
821 return true;
822 }
823 }
824 return false;
825}
826
827/**
828 * dma_fence_wait_any_timeout - sleep until any fence gets signaled
829 * or until timeout elapses
830 * @fences: array of fences to wait on
831 * @count: number of fences to wait on
832 * @intr: if true, do an interruptible wait
833 * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
834 * @idx: used to store the first signaled fence index, meaningful only on
835 * positive return
836 *
837 * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
838 * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
839 * on success.
840 *
841 * Synchronous waits for the first fence in the array to be signaled. The
842 * caller needs to hold a reference to all fences in the array, otherwise a
843 * fence might be freed before return, resulting in undefined behavior.
844 *
845 * See also dma_fence_wait() and dma_fence_wait_timeout().
846 */
847signed long
848dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
849 bool intr, signed long timeout, uint32_t *idx)
850{
851 struct default_wait_cb *cb;
852 signed long ret = timeout;
853 unsigned i;
854
855 if (WARN_ON(!fences || !count || timeout < 0))
856 return -EINVAL;
857
858 if (timeout == 0) {
859 for (i = 0; i < count; ++i)
860 if (dma_fence_is_signaled(fences[i])) {
861 if (idx)
862 *idx = i;
863 return 1;
864 }
865
866 return 0;
867 }
868
869 cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
870 if (cb == NULL) {
871 ret = -ENOMEM;
872 goto err_free_cb;
873 }
874
875 for (i = 0; i < count; ++i) {
876 struct dma_fence *fence = fences[i];
877
878 cb[i].task = current;
879 if (dma_fence_add_callback(fence, &cb[i].base,
880 dma_fence_default_wait_cb)) {
881 /* This fence is already signaled */
882 if (idx)
883 *idx = i;
884 goto fence_rm_cb;
885 }
886 }
887
888 while (ret > 0) {
889 if (intr)
890 set_current_state(TASK_INTERRUPTIBLE);
891 else
892 set_current_state(TASK_UNINTERRUPTIBLE);
893
894 if (dma_fence_test_signaled_any(fences, count, idx))
895 break;
896
897 ret = schedule_timeout(ret);
898
899 if (ret > 0 && intr && signal_pending(current))
900 ret = -ERESTARTSYS;
901 }
902
903 __set_current_state(TASK_RUNNING);
904
905fence_rm_cb:
906 while (i-- > 0)
907 dma_fence_remove_callback(fences[i], &cb[i].base);
908
909err_free_cb:
910 kfree(cb);
911
912 return ret;
913}
914EXPORT_SYMBOL(dma_fence_wait_any_timeout);
915
916/**
917 * DOC: deadline hints
918 *
919 * In an ideal world, it would be possible to pipeline a workload sufficiently
920 * that a utilization based device frequency governor could arrive at a minimum
921 * frequency that meets the requirements of the use-case, in order to minimize
922 * power consumption. But in the real world there are many workloads which
923 * defy this ideal. For example, but not limited to:
924 *
925 * * Workloads that ping-pong between device and CPU, with alternating periods
926 * of CPU waiting for device, and device waiting on CPU. This can result in
927 * devfreq and cpufreq seeing idle time in their respective domains and in
928 * result reduce frequency.
929 *
930 * * Workloads that interact with a periodic time based deadline, such as double
931 * buffered GPU rendering vs vblank sync'd page flipping. In this scenario,
932 * missing a vblank deadline results in an *increase* in idle time on the GPU
933 * (since it has to wait an additional vblank period), sending a signal to
934 * the GPU's devfreq to reduce frequency, when in fact the opposite is what is
935 * needed.
936 *
937 * To this end, deadline hint(s) can be set on a &dma_fence via &dma_fence_set_deadline
938 * (or indirectly via userspace facing ioctls like &sync_set_deadline).
939 * The deadline hint provides a way for the waiting driver, or userspace, to
940 * convey an appropriate sense of urgency to the signaling driver.
941 *
942 * A deadline hint is given in absolute ktime (CLOCK_MONOTONIC for userspace
943 * facing APIs). The time could either be some point in the future (such as
944 * the vblank based deadline for page-flipping, or the start of a compositor's
945 * composition cycle), or the current time to indicate an immediate deadline
946 * hint (Ie. forward progress cannot be made until this fence is signaled).
947 *
948 * Multiple deadlines may be set on a given fence, even in parallel. See the
949 * documentation for &dma_fence_ops.set_deadline.
950 *
951 * The deadline hint is just that, a hint. The driver that created the fence
952 * may react by increasing frequency, making different scheduling choices, etc.
953 * Or doing nothing at all.
954 */
955
956/**
957 * dma_fence_set_deadline - set desired fence-wait deadline hint
958 * @fence: the fence that is to be waited on
959 * @deadline: the time by which the waiter hopes for the fence to be
960 * signaled
961 *
962 * Give the fence signaler a hint about an upcoming deadline, such as
963 * vblank, by which point the waiter would prefer the fence to be
964 * signaled by. This is intended to give feedback to the fence signaler
965 * to aid in power management decisions, such as boosting GPU frequency
966 * if a periodic vblank deadline is approaching but the fence is not
967 * yet signaled..
968 */
969void dma_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
970{
971 if (fence->ops->set_deadline && !dma_fence_is_signaled(fence))
972 fence->ops->set_deadline(fence, deadline);
973}
974EXPORT_SYMBOL(dma_fence_set_deadline);
975
976/**
977 * dma_fence_describe - Dump fence describtion into seq_file
978 * @fence: the 6fence to describe
979 * @seq: the seq_file to put the textual description into
980 *
981 * Dump a textual description of the fence and it's state into the seq_file.
982 */
983void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq)
984{
985 seq_printf(seq, "%s %s seq %llu %ssignalled\n",
986 fence->ops->get_driver_name(fence),
987 fence->ops->get_timeline_name(fence), fence->seqno,
988 dma_fence_is_signaled(fence) ? "" : "un");
989}
990EXPORT_SYMBOL(dma_fence_describe);
991
992/**
993 * dma_fence_init - Initialize a custom fence.
994 * @fence: the fence to initialize
995 * @ops: the dma_fence_ops for operations on this fence
996 * @lock: the irqsafe spinlock to use for locking this fence
997 * @context: the execution context this fence is run on
998 * @seqno: a linear increasing sequence number for this context
999 *
1000 * Initializes an allocated fence, the caller doesn't have to keep its
1001 * refcount after committing with this fence, but it will need to hold a
1002 * refcount again if &dma_fence_ops.enable_signaling gets called.
1003 *
1004 * context and seqno are used for easy comparison between fences, allowing
1005 * to check which fence is later by simply using dma_fence_later().
1006 */
1007void
1008dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
1009 spinlock_t *lock, u64 context, u64 seqno)
1010{
1011 BUG_ON(!lock);
1012 BUG_ON(!ops || !ops->get_driver_name || !ops->get_timeline_name);
1013
1014 kref_init(&fence->refcount);
1015 fence->ops = ops;
1016 INIT_LIST_HEAD(&fence->cb_list);
1017 fence->lock = lock;
1018 fence->context = context;
1019 fence->seqno = seqno;
1020 fence->flags = 0UL;
1021 fence->error = 0;
1022
1023 trace_dma_fence_init(fence);
1024}
1025EXPORT_SYMBOL(dma_fence_init);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Fence mechanism for dma-buf and 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#include <linux/slab.h>
14#include <linux/export.h>
15#include <linux/atomic.h>
16#include <linux/dma-fence.h>
17#include <linux/sched/signal.h>
18#include <linux/seq_file.h>
19
20#define CREATE_TRACE_POINTS
21#include <trace/events/dma_fence.h>
22
23EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
24EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
25EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
26
27static DEFINE_SPINLOCK(dma_fence_stub_lock);
28static struct dma_fence dma_fence_stub;
29
30/*
31 * fence context counter: each execution context should have its own
32 * fence context, this allows checking if fences belong to the same
33 * context or not. One device can have multiple separate contexts,
34 * and they're used if some engine can run independently of another.
35 */
36static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(1);
37
38/**
39 * DOC: DMA fences overview
40 *
41 * DMA fences, represented by &struct dma_fence, are the kernel internal
42 * synchronization primitive for DMA operations like GPU rendering, video
43 * encoding/decoding, or displaying buffers on a screen.
44 *
45 * A fence is initialized using dma_fence_init() and completed using
46 * dma_fence_signal(). Fences are associated with a context, allocated through
47 * dma_fence_context_alloc(), and all fences on the same context are
48 * fully ordered.
49 *
50 * Since the purposes of fences is to facilitate cross-device and
51 * cross-application synchronization, there's multiple ways to use one:
52 *
53 * - Individual fences can be exposed as a &sync_file, accessed as a file
54 * descriptor from userspace, created by calling sync_file_create(). This is
55 * called explicit fencing, since userspace passes around explicit
56 * synchronization points.
57 *
58 * - Some subsystems also have their own explicit fencing primitives, like
59 * &drm_syncobj. Compared to &sync_file, a &drm_syncobj allows the underlying
60 * fence to be updated.
61 *
62 * - Then there's also implicit fencing, where the synchronization points are
63 * implicitly passed around as part of shared &dma_buf instances. Such
64 * implicit fences are stored in &struct dma_resv through the
65 * &dma_buf.resv pointer.
66 */
67
68/**
69 * DOC: fence cross-driver contract
70 *
71 * Since &dma_fence provide a cross driver contract, all drivers must follow the
72 * same rules:
73 *
74 * * Fences must complete in a reasonable time. Fences which represent kernels
75 * and shaders submitted by userspace, which could run forever, must be backed
76 * up by timeout and gpu hang recovery code. Minimally that code must prevent
77 * further command submission and force complete all in-flight fences, e.g.
78 * when the driver or hardware do not support gpu reset, or if the gpu reset
79 * failed for some reason. Ideally the driver supports gpu recovery which only
80 * affects the offending userspace context, and no other userspace
81 * submissions.
82 *
83 * * Drivers may have different ideas of what completion within a reasonable
84 * time means. Some hang recovery code uses a fixed timeout, others a mix
85 * between observing forward progress and increasingly strict timeouts.
86 * Drivers should not try to second guess timeout handling of fences from
87 * other drivers.
88 *
89 * * To ensure there's no deadlocks of dma_fence_wait() against other locks
90 * drivers should annotate all code required to reach dma_fence_signal(),
91 * which completes the fences, with dma_fence_begin_signalling() and
92 * dma_fence_end_signalling().
93 *
94 * * Drivers are allowed to call dma_fence_wait() while holding dma_resv_lock().
95 * This means any code required for fence completion cannot acquire a
96 * &dma_resv lock. Note that this also pulls in the entire established
97 * locking hierarchy around dma_resv_lock() and dma_resv_unlock().
98 *
99 * * Drivers are allowed to call dma_fence_wait() from their &shrinker
100 * callbacks. This means any code required for fence completion cannot
101 * allocate memory with GFP_KERNEL.
102 *
103 * * Drivers are allowed to call dma_fence_wait() from their &mmu_notifier
104 * respectively &mmu_interval_notifier callbacks. This means any code required
105 * for fence completeion cannot allocate memory with GFP_NOFS or GFP_NOIO.
106 * Only GFP_ATOMIC is permissible, which might fail.
107 *
108 * Note that only GPU drivers have a reasonable excuse for both requiring
109 * &mmu_interval_notifier and &shrinker callbacks at the same time as having to
110 * track asynchronous compute work using &dma_fence. No driver outside of
111 * drivers/gpu should ever call dma_fence_wait() in such contexts.
112 */
113
114static const char *dma_fence_stub_get_name(struct dma_fence *fence)
115{
116 return "stub";
117}
118
119static const struct dma_fence_ops dma_fence_stub_ops = {
120 .get_driver_name = dma_fence_stub_get_name,
121 .get_timeline_name = dma_fence_stub_get_name,
122};
123
124/**
125 * dma_fence_get_stub - return a signaled fence
126 *
127 * Return a stub fence which is already signaled. The fence's
128 * timestamp corresponds to the first time after boot this
129 * function is called.
130 */
131struct dma_fence *dma_fence_get_stub(void)
132{
133 spin_lock(&dma_fence_stub_lock);
134 if (!dma_fence_stub.ops) {
135 dma_fence_init(&dma_fence_stub,
136 &dma_fence_stub_ops,
137 &dma_fence_stub_lock,
138 0, 0);
139
140 set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
141 &dma_fence_stub.flags);
142
143 dma_fence_signal_locked(&dma_fence_stub);
144 }
145 spin_unlock(&dma_fence_stub_lock);
146
147 return dma_fence_get(&dma_fence_stub);
148}
149EXPORT_SYMBOL(dma_fence_get_stub);
150
151/**
152 * dma_fence_allocate_private_stub - return a private, signaled fence
153 *
154 * Return a newly allocated and signaled stub fence.
155 */
156struct dma_fence *dma_fence_allocate_private_stub(void)
157{
158 struct dma_fence *fence;
159
160 fence = kzalloc(sizeof(*fence), GFP_KERNEL);
161 if (fence == NULL)
162 return ERR_PTR(-ENOMEM);
163
164 dma_fence_init(fence,
165 &dma_fence_stub_ops,
166 &dma_fence_stub_lock,
167 0, 0);
168
169 set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
170 &fence->flags);
171
172 dma_fence_signal(fence);
173
174 return fence;
175}
176EXPORT_SYMBOL(dma_fence_allocate_private_stub);
177
178/**
179 * dma_fence_context_alloc - allocate an array of fence contexts
180 * @num: amount of contexts to allocate
181 *
182 * This function will return the first index of the number of fence contexts
183 * allocated. The fence context is used for setting &dma_fence.context to a
184 * unique number by passing the context to dma_fence_init().
185 */
186u64 dma_fence_context_alloc(unsigned num)
187{
188 WARN_ON(!num);
189 return atomic64_fetch_add(num, &dma_fence_context_counter);
190}
191EXPORT_SYMBOL(dma_fence_context_alloc);
192
193/**
194 * DOC: fence signalling annotation
195 *
196 * Proving correctness of all the kernel code around &dma_fence through code
197 * review and testing is tricky for a few reasons:
198 *
199 * * It is a cross-driver contract, and therefore all drivers must follow the
200 * same rules for lock nesting order, calling contexts for various functions
201 * and anything else significant for in-kernel interfaces. But it is also
202 * impossible to test all drivers in a single machine, hence brute-force N vs.
203 * N testing of all combinations is impossible. Even just limiting to the
204 * possible combinations is infeasible.
205 *
206 * * There is an enormous amount of driver code involved. For render drivers
207 * there's the tail of command submission, after fences are published,
208 * scheduler code, interrupt and workers to process job completion,
209 * and timeout, gpu reset and gpu hang recovery code. Plus for integration
210 * with core mm with have &mmu_notifier, respectively &mmu_interval_notifier,
211 * and &shrinker. For modesetting drivers there's the commit tail functions
212 * between when fences for an atomic modeset are published, and when the
213 * corresponding vblank completes, including any interrupt processing and
214 * related workers. Auditing all that code, across all drivers, is not
215 * feasible.
216 *
217 * * Due to how many other subsystems are involved and the locking hierarchies
218 * this pulls in there is extremely thin wiggle-room for driver-specific
219 * differences. &dma_fence interacts with almost all of the core memory
220 * handling through page fault handlers via &dma_resv, dma_resv_lock() and
221 * dma_resv_unlock(). On the other side it also interacts through all
222 * allocation sites through &mmu_notifier and &shrinker.
223 *
224 * Furthermore lockdep does not handle cross-release dependencies, which means
225 * any deadlocks between dma_fence_wait() and dma_fence_signal() can't be caught
226 * at runtime with some quick testing. The simplest example is one thread
227 * waiting on a &dma_fence while holding a lock::
228 *
229 * lock(A);
230 * dma_fence_wait(B);
231 * unlock(A);
232 *
233 * while the other thread is stuck trying to acquire the same lock, which
234 * prevents it from signalling the fence the previous thread is stuck waiting
235 * on::
236 *
237 * lock(A);
238 * unlock(A);
239 * dma_fence_signal(B);
240 *
241 * By manually annotating all code relevant to signalling a &dma_fence we can
242 * teach lockdep about these dependencies, which also helps with the validation
243 * headache since now lockdep can check all the rules for us::
244 *
245 * cookie = dma_fence_begin_signalling();
246 * lock(A);
247 * unlock(A);
248 * dma_fence_signal(B);
249 * dma_fence_end_signalling(cookie);
250 *
251 * For using dma_fence_begin_signalling() and dma_fence_end_signalling() to
252 * annotate critical sections the following rules need to be observed:
253 *
254 * * All code necessary to complete a &dma_fence must be annotated, from the
255 * point where a fence is accessible to other threads, to the point where
256 * dma_fence_signal() is called. Un-annotated code can contain deadlock issues,
257 * and due to the very strict rules and many corner cases it is infeasible to
258 * catch these just with review or normal stress testing.
259 *
260 * * &struct dma_resv deserves a special note, since the readers are only
261 * protected by rcu. This means the signalling critical section starts as soon
262 * as the new fences are installed, even before dma_resv_unlock() is called.
263 *
264 * * The only exception are fast paths and opportunistic signalling code, which
265 * calls dma_fence_signal() purely as an optimization, but is not required to
266 * guarantee completion of a &dma_fence. The usual example is a wait IOCTL
267 * which calls dma_fence_signal(), while the mandatory completion path goes
268 * through a hardware interrupt and possible job completion worker.
269 *
270 * * To aid composability of code, the annotations can be freely nested, as long
271 * as the overall locking hierarchy is consistent. The annotations also work
272 * both in interrupt and process context. Due to implementation details this
273 * requires that callers pass an opaque cookie from
274 * dma_fence_begin_signalling() to dma_fence_end_signalling().
275 *
276 * * Validation against the cross driver contract is implemented by priming
277 * lockdep with the relevant hierarchy at boot-up. This means even just
278 * testing with a single device is enough to validate a driver, at least as
279 * far as deadlocks with dma_fence_wait() against dma_fence_signal() are
280 * concerned.
281 */
282#ifdef CONFIG_LOCKDEP
283static struct lockdep_map dma_fence_lockdep_map = {
284 .name = "dma_fence_map"
285};
286
287/**
288 * dma_fence_begin_signalling - begin a critical DMA fence signalling section
289 *
290 * Drivers should use this to annotate the beginning of any code section
291 * required to eventually complete &dma_fence by calling dma_fence_signal().
292 *
293 * The end of these critical sections are annotated with
294 * dma_fence_end_signalling().
295 *
296 * Returns:
297 *
298 * Opaque cookie needed by the implementation, which needs to be passed to
299 * dma_fence_end_signalling().
300 */
301bool dma_fence_begin_signalling(void)
302{
303 /* explicitly nesting ... */
304 if (lock_is_held_type(&dma_fence_lockdep_map, 1))
305 return true;
306
307 /* rely on might_sleep check for soft/hardirq locks */
308 if (in_atomic())
309 return true;
310
311 /* ... and non-recursive readlock */
312 lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _RET_IP_);
313
314 return false;
315}
316EXPORT_SYMBOL(dma_fence_begin_signalling);
317
318/**
319 * dma_fence_end_signalling - end a critical DMA fence signalling section
320 * @cookie: opaque cookie from dma_fence_begin_signalling()
321 *
322 * Closes a critical section annotation opened by dma_fence_begin_signalling().
323 */
324void dma_fence_end_signalling(bool cookie)
325{
326 if (cookie)
327 return;
328
329 lock_release(&dma_fence_lockdep_map, _RET_IP_);
330}
331EXPORT_SYMBOL(dma_fence_end_signalling);
332
333void __dma_fence_might_wait(void)
334{
335 bool tmp;
336
337 tmp = lock_is_held_type(&dma_fence_lockdep_map, 1);
338 if (tmp)
339 lock_release(&dma_fence_lockdep_map, _THIS_IP_);
340 lock_map_acquire(&dma_fence_lockdep_map);
341 lock_map_release(&dma_fence_lockdep_map);
342 if (tmp)
343 lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _THIS_IP_);
344}
345#endif
346
347
348/**
349 * dma_fence_signal_timestamp_locked - signal completion of a fence
350 * @fence: the fence to signal
351 * @timestamp: fence signal timestamp in kernel's CLOCK_MONOTONIC time domain
352 *
353 * Signal completion for software callbacks on a fence, this will unblock
354 * dma_fence_wait() calls and run all the callbacks added with
355 * dma_fence_add_callback(). Can be called multiple times, but since a fence
356 * can only go from the unsignaled to the signaled state and not back, it will
357 * only be effective the first time. Set the timestamp provided as the fence
358 * signal timestamp.
359 *
360 * Unlike dma_fence_signal_timestamp(), this function must be called with
361 * &dma_fence.lock held.
362 *
363 * Returns 0 on success and a negative error value when @fence has been
364 * signalled already.
365 */
366int dma_fence_signal_timestamp_locked(struct dma_fence *fence,
367 ktime_t timestamp)
368{
369 struct dma_fence_cb *cur, *tmp;
370 struct list_head cb_list;
371
372 lockdep_assert_held(fence->lock);
373
374 if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
375 &fence->flags)))
376 return -EINVAL;
377
378 /* Stash the cb_list before replacing it with the timestamp */
379 list_replace(&fence->cb_list, &cb_list);
380
381 fence->timestamp = timestamp;
382 set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
383 trace_dma_fence_signaled(fence);
384
385 list_for_each_entry_safe(cur, tmp, &cb_list, node) {
386 INIT_LIST_HEAD(&cur->node);
387 cur->func(fence, cur);
388 }
389
390 return 0;
391}
392EXPORT_SYMBOL(dma_fence_signal_timestamp_locked);
393
394/**
395 * dma_fence_signal_timestamp - signal completion of a fence
396 * @fence: the fence to signal
397 * @timestamp: fence signal timestamp in kernel's CLOCK_MONOTONIC time domain
398 *
399 * Signal completion for software callbacks on a fence, this will unblock
400 * dma_fence_wait() calls and run all the callbacks added with
401 * dma_fence_add_callback(). Can be called multiple times, but since a fence
402 * can only go from the unsignaled to the signaled state and not back, it will
403 * only be effective the first time. Set the timestamp provided as the fence
404 * signal timestamp.
405 *
406 * Returns 0 on success and a negative error value when @fence has been
407 * signalled already.
408 */
409int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp)
410{
411 unsigned long flags;
412 int ret;
413
414 if (!fence)
415 return -EINVAL;
416
417 spin_lock_irqsave(fence->lock, flags);
418 ret = dma_fence_signal_timestamp_locked(fence, timestamp);
419 spin_unlock_irqrestore(fence->lock, flags);
420
421 return ret;
422}
423EXPORT_SYMBOL(dma_fence_signal_timestamp);
424
425/**
426 * dma_fence_signal_locked - signal completion of a fence
427 * @fence: the fence to signal
428 *
429 * Signal completion for software callbacks on a fence, this will unblock
430 * dma_fence_wait() calls and run all the callbacks added with
431 * dma_fence_add_callback(). Can be called multiple times, but since a fence
432 * can only go from the unsignaled to the signaled state and not back, it will
433 * only be effective the first time.
434 *
435 * Unlike dma_fence_signal(), this function must be called with &dma_fence.lock
436 * held.
437 *
438 * Returns 0 on success and a negative error value when @fence has been
439 * signalled already.
440 */
441int dma_fence_signal_locked(struct dma_fence *fence)
442{
443 return dma_fence_signal_timestamp_locked(fence, ktime_get());
444}
445EXPORT_SYMBOL(dma_fence_signal_locked);
446
447/**
448 * dma_fence_signal - signal completion of a fence
449 * @fence: the fence to signal
450 *
451 * Signal completion for software callbacks on a fence, this will unblock
452 * dma_fence_wait() calls and run all the callbacks added with
453 * dma_fence_add_callback(). Can be called multiple times, but since a fence
454 * can only go from the unsignaled to the signaled state and not back, it will
455 * only be effective the first time.
456 *
457 * Returns 0 on success and a negative error value when @fence has been
458 * signalled already.
459 */
460int dma_fence_signal(struct dma_fence *fence)
461{
462 unsigned long flags;
463 int ret;
464 bool tmp;
465
466 if (!fence)
467 return -EINVAL;
468
469 tmp = dma_fence_begin_signalling();
470
471 spin_lock_irqsave(fence->lock, flags);
472 ret = dma_fence_signal_timestamp_locked(fence, ktime_get());
473 spin_unlock_irqrestore(fence->lock, flags);
474
475 dma_fence_end_signalling(tmp);
476
477 return ret;
478}
479EXPORT_SYMBOL(dma_fence_signal);
480
481/**
482 * dma_fence_wait_timeout - sleep until the fence gets signaled
483 * or until timeout elapses
484 * @fence: the fence to wait on
485 * @intr: if true, do an interruptible wait
486 * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
487 *
488 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
489 * remaining timeout in jiffies on success. Other error values may be
490 * returned on custom implementations.
491 *
492 * Performs a synchronous wait on this fence. It is assumed the caller
493 * directly or indirectly (buf-mgr between reservation and committing)
494 * holds a reference to the fence, otherwise the fence might be
495 * freed before return, resulting in undefined behavior.
496 *
497 * See also dma_fence_wait() and dma_fence_wait_any_timeout().
498 */
499signed long
500dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
501{
502 signed long ret;
503
504 if (WARN_ON(timeout < 0))
505 return -EINVAL;
506
507 might_sleep();
508
509 __dma_fence_might_wait();
510
511 dma_fence_enable_sw_signaling(fence);
512
513 trace_dma_fence_wait_start(fence);
514 if (fence->ops->wait)
515 ret = fence->ops->wait(fence, intr, timeout);
516 else
517 ret = dma_fence_default_wait(fence, intr, timeout);
518 trace_dma_fence_wait_end(fence);
519 return ret;
520}
521EXPORT_SYMBOL(dma_fence_wait_timeout);
522
523/**
524 * dma_fence_release - default relese function for fences
525 * @kref: &dma_fence.recfount
526 *
527 * This is the default release functions for &dma_fence. Drivers shouldn't call
528 * this directly, but instead call dma_fence_put().
529 */
530void dma_fence_release(struct kref *kref)
531{
532 struct dma_fence *fence =
533 container_of(kref, struct dma_fence, refcount);
534
535 trace_dma_fence_destroy(fence);
536
537 if (WARN(!list_empty(&fence->cb_list) &&
538 !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags),
539 "Fence %s:%s:%llx:%llx released with pending signals!\n",
540 fence->ops->get_driver_name(fence),
541 fence->ops->get_timeline_name(fence),
542 fence->context, fence->seqno)) {
543 unsigned long flags;
544
545 /*
546 * Failed to signal before release, likely a refcounting issue.
547 *
548 * This should never happen, but if it does make sure that we
549 * don't leave chains dangling. We set the error flag first
550 * so that the callbacks know this signal is due to an error.
551 */
552 spin_lock_irqsave(fence->lock, flags);
553 fence->error = -EDEADLK;
554 dma_fence_signal_locked(fence);
555 spin_unlock_irqrestore(fence->lock, flags);
556 }
557
558 if (fence->ops->release)
559 fence->ops->release(fence);
560 else
561 dma_fence_free(fence);
562}
563EXPORT_SYMBOL(dma_fence_release);
564
565/**
566 * dma_fence_free - default release function for &dma_fence.
567 * @fence: fence to release
568 *
569 * This is the default implementation for &dma_fence_ops.release. It calls
570 * kfree_rcu() on @fence.
571 */
572void dma_fence_free(struct dma_fence *fence)
573{
574 kfree_rcu(fence, rcu);
575}
576EXPORT_SYMBOL(dma_fence_free);
577
578static bool __dma_fence_enable_signaling(struct dma_fence *fence)
579{
580 bool was_set;
581
582 lockdep_assert_held(fence->lock);
583
584 was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
585 &fence->flags);
586
587 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
588 return false;
589
590 if (!was_set && fence->ops->enable_signaling) {
591 trace_dma_fence_enable_signal(fence);
592
593 if (!fence->ops->enable_signaling(fence)) {
594 dma_fence_signal_locked(fence);
595 return false;
596 }
597 }
598
599 return true;
600}
601
602/**
603 * dma_fence_enable_sw_signaling - enable signaling on fence
604 * @fence: the fence to enable
605 *
606 * This will request for sw signaling to be enabled, to make the fence
607 * complete as soon as possible. This calls &dma_fence_ops.enable_signaling
608 * internally.
609 */
610void dma_fence_enable_sw_signaling(struct dma_fence *fence)
611{
612 unsigned long flags;
613
614 spin_lock_irqsave(fence->lock, flags);
615 __dma_fence_enable_signaling(fence);
616 spin_unlock_irqrestore(fence->lock, flags);
617}
618EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
619
620/**
621 * dma_fence_add_callback - add a callback to be called when the fence
622 * is signaled
623 * @fence: the fence to wait on
624 * @cb: the callback to register
625 * @func: the function to call
626 *
627 * Add a software callback to the fence. The caller should keep a reference to
628 * the fence.
629 *
630 * @cb will be initialized by dma_fence_add_callback(), no initialization
631 * by the caller is required. Any number of callbacks can be registered
632 * to a fence, but a callback can only be registered to one fence at a time.
633 *
634 * If fence is already signaled, this function will return -ENOENT (and
635 * *not* call the callback).
636 *
637 * Note that the callback can be called from an atomic context or irq context.
638 *
639 * Returns 0 in case of success, -ENOENT if the fence is already signaled
640 * and -EINVAL in case of error.
641 */
642int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
643 dma_fence_func_t func)
644{
645 unsigned long flags;
646 int ret = 0;
647
648 if (WARN_ON(!fence || !func))
649 return -EINVAL;
650
651 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
652 INIT_LIST_HEAD(&cb->node);
653 return -ENOENT;
654 }
655
656 spin_lock_irqsave(fence->lock, flags);
657
658 if (__dma_fence_enable_signaling(fence)) {
659 cb->func = func;
660 list_add_tail(&cb->node, &fence->cb_list);
661 } else {
662 INIT_LIST_HEAD(&cb->node);
663 ret = -ENOENT;
664 }
665
666 spin_unlock_irqrestore(fence->lock, flags);
667
668 return ret;
669}
670EXPORT_SYMBOL(dma_fence_add_callback);
671
672/**
673 * dma_fence_get_status - returns the status upon completion
674 * @fence: the dma_fence to query
675 *
676 * This wraps dma_fence_get_status_locked() to return the error status
677 * condition on a signaled fence. See dma_fence_get_status_locked() for more
678 * details.
679 *
680 * Returns 0 if the fence has not yet been signaled, 1 if the fence has
681 * been signaled without an error condition, or a negative error code
682 * if the fence has been completed in err.
683 */
684int dma_fence_get_status(struct dma_fence *fence)
685{
686 unsigned long flags;
687 int status;
688
689 spin_lock_irqsave(fence->lock, flags);
690 status = dma_fence_get_status_locked(fence);
691 spin_unlock_irqrestore(fence->lock, flags);
692
693 return status;
694}
695EXPORT_SYMBOL(dma_fence_get_status);
696
697/**
698 * dma_fence_remove_callback - remove a callback from the signaling list
699 * @fence: the fence to wait on
700 * @cb: the callback to remove
701 *
702 * Remove a previously queued callback from the fence. This function returns
703 * true if the callback is successfully removed, or false if the fence has
704 * already been signaled.
705 *
706 * *WARNING*:
707 * Cancelling a callback should only be done if you really know what you're
708 * doing, since deadlocks and race conditions could occur all too easily. For
709 * this reason, it should only ever be done on hardware lockup recovery,
710 * with a reference held to the fence.
711 *
712 * Behaviour is undefined if @cb has not been added to @fence using
713 * dma_fence_add_callback() beforehand.
714 */
715bool
716dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb)
717{
718 unsigned long flags;
719 bool ret;
720
721 spin_lock_irqsave(fence->lock, flags);
722
723 ret = !list_empty(&cb->node);
724 if (ret)
725 list_del_init(&cb->node);
726
727 spin_unlock_irqrestore(fence->lock, flags);
728
729 return ret;
730}
731EXPORT_SYMBOL(dma_fence_remove_callback);
732
733struct default_wait_cb {
734 struct dma_fence_cb base;
735 struct task_struct *task;
736};
737
738static void
739dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
740{
741 struct default_wait_cb *wait =
742 container_of(cb, struct default_wait_cb, base);
743
744 wake_up_state(wait->task, TASK_NORMAL);
745}
746
747/**
748 * dma_fence_default_wait - default sleep until the fence gets signaled
749 * or until timeout elapses
750 * @fence: the fence to wait on
751 * @intr: if true, do an interruptible wait
752 * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
753 *
754 * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
755 * remaining timeout in jiffies on success. If timeout is zero the value one is
756 * returned if the fence is already signaled for consistency with other
757 * functions taking a jiffies timeout.
758 */
759signed long
760dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
761{
762 struct default_wait_cb cb;
763 unsigned long flags;
764 signed long ret = timeout ? timeout : 1;
765
766 spin_lock_irqsave(fence->lock, flags);
767
768 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
769 goto out;
770
771 if (intr && signal_pending(current)) {
772 ret = -ERESTARTSYS;
773 goto out;
774 }
775
776 if (!timeout) {
777 ret = 0;
778 goto out;
779 }
780
781 cb.base.func = dma_fence_default_wait_cb;
782 cb.task = current;
783 list_add(&cb.base.node, &fence->cb_list);
784
785 while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
786 if (intr)
787 __set_current_state(TASK_INTERRUPTIBLE);
788 else
789 __set_current_state(TASK_UNINTERRUPTIBLE);
790 spin_unlock_irqrestore(fence->lock, flags);
791
792 ret = schedule_timeout(ret);
793
794 spin_lock_irqsave(fence->lock, flags);
795 if (ret > 0 && intr && signal_pending(current))
796 ret = -ERESTARTSYS;
797 }
798
799 if (!list_empty(&cb.base.node))
800 list_del(&cb.base.node);
801 __set_current_state(TASK_RUNNING);
802
803out:
804 spin_unlock_irqrestore(fence->lock, flags);
805 return ret;
806}
807EXPORT_SYMBOL(dma_fence_default_wait);
808
809static bool
810dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count,
811 uint32_t *idx)
812{
813 int i;
814
815 for (i = 0; i < count; ++i) {
816 struct dma_fence *fence = fences[i];
817 if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
818 if (idx)
819 *idx = i;
820 return true;
821 }
822 }
823 return false;
824}
825
826/**
827 * dma_fence_wait_any_timeout - sleep until any fence gets signaled
828 * or until timeout elapses
829 * @fences: array of fences to wait on
830 * @count: number of fences to wait on
831 * @intr: if true, do an interruptible wait
832 * @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
833 * @idx: used to store the first signaled fence index, meaningful only on
834 * positive return
835 *
836 * Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
837 * interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
838 * on success.
839 *
840 * Synchronous waits for the first fence in the array to be signaled. The
841 * caller needs to hold a reference to all fences in the array, otherwise a
842 * fence might be freed before return, resulting in undefined behavior.
843 *
844 * See also dma_fence_wait() and dma_fence_wait_timeout().
845 */
846signed long
847dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
848 bool intr, signed long timeout, uint32_t *idx)
849{
850 struct default_wait_cb *cb;
851 signed long ret = timeout;
852 unsigned i;
853
854 if (WARN_ON(!fences || !count || timeout < 0))
855 return -EINVAL;
856
857 if (timeout == 0) {
858 for (i = 0; i < count; ++i)
859 if (dma_fence_is_signaled(fences[i])) {
860 if (idx)
861 *idx = i;
862 return 1;
863 }
864
865 return 0;
866 }
867
868 cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
869 if (cb == NULL) {
870 ret = -ENOMEM;
871 goto err_free_cb;
872 }
873
874 for (i = 0; i < count; ++i) {
875 struct dma_fence *fence = fences[i];
876
877 cb[i].task = current;
878 if (dma_fence_add_callback(fence, &cb[i].base,
879 dma_fence_default_wait_cb)) {
880 /* This fence is already signaled */
881 if (idx)
882 *idx = i;
883 goto fence_rm_cb;
884 }
885 }
886
887 while (ret > 0) {
888 if (intr)
889 set_current_state(TASK_INTERRUPTIBLE);
890 else
891 set_current_state(TASK_UNINTERRUPTIBLE);
892
893 if (dma_fence_test_signaled_any(fences, count, idx))
894 break;
895
896 ret = schedule_timeout(ret);
897
898 if (ret > 0 && intr && signal_pending(current))
899 ret = -ERESTARTSYS;
900 }
901
902 __set_current_state(TASK_RUNNING);
903
904fence_rm_cb:
905 while (i-- > 0)
906 dma_fence_remove_callback(fences[i], &cb[i].base);
907
908err_free_cb:
909 kfree(cb);
910
911 return ret;
912}
913EXPORT_SYMBOL(dma_fence_wait_any_timeout);
914
915/**
916 * dma_fence_describe - Dump fence describtion into seq_file
917 * @fence: the 6fence to describe
918 * @seq: the seq_file to put the textual description into
919 *
920 * Dump a textual description of the fence and it's state into the seq_file.
921 */
922void dma_fence_describe(struct dma_fence *fence, struct seq_file *seq)
923{
924 seq_printf(seq, "%s %s seq %llu %ssignalled\n",
925 fence->ops->get_driver_name(fence),
926 fence->ops->get_timeline_name(fence), fence->seqno,
927 dma_fence_is_signaled(fence) ? "" : "un");
928}
929EXPORT_SYMBOL(dma_fence_describe);
930
931/**
932 * dma_fence_init - Initialize a custom fence.
933 * @fence: the fence to initialize
934 * @ops: the dma_fence_ops for operations on this fence
935 * @lock: the irqsafe spinlock to use for locking this fence
936 * @context: the execution context this fence is run on
937 * @seqno: a linear increasing sequence number for this context
938 *
939 * Initializes an allocated fence, the caller doesn't have to keep its
940 * refcount after committing with this fence, but it will need to hold a
941 * refcount again if &dma_fence_ops.enable_signaling gets called.
942 *
943 * context and seqno are used for easy comparison between fences, allowing
944 * to check which fence is later by simply using dma_fence_later().
945 */
946void
947dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
948 spinlock_t *lock, u64 context, u64 seqno)
949{
950 BUG_ON(!lock);
951 BUG_ON(!ops || !ops->get_driver_name || !ops->get_timeline_name);
952
953 kref_init(&fence->refcount);
954 fence->ops = ops;
955 INIT_LIST_HEAD(&fence->cb_list);
956 fence->lock = lock;
957 fence->context = context;
958 fence->seqno = seqno;
959 fence->flags = 0UL;
960 fence->error = 0;
961
962 trace_dma_fence_init(fence);
963}
964EXPORT_SYMBOL(dma_fence_init);