Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
dma-buf: detach fence ops on signal v3
When neither a release nor a wait backend ops is specified it is possible
to let the dma_fence live on independently of the module who issued it.
This makes it possible to unload drivers and only wait for all their
fences to signal.
v2: fix typo in comment
v3: fix sparse rcu warnings
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Philipp Stanner <phasta@kernel.org>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/r/20260219160822.1529-3-christian.koenig@amd.com
+16
-6
+14
-4
drivers/dma-buf/dma-fence.c
+14
-4
drivers/dma-buf/dma-fence.c
···
362
362
void dma_fence_signal_timestamp_locked(struct dma_fence *fence,
363
363
ktime_t timestamp)
364
364
{
365
+
const struct dma_fence_ops *ops;
365
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struct dma_fence_cb *cur, *tmp;
366
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struct list_head cb_list;
367
368
···
371
370
if (unlikely(test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT,
372
371
&fence->flags)))
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372
return;
373
+
374
+
/*
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+
* When neither a release nor a wait operation is specified set the ops
376
+
* pointer to NULL to allow the fence structure to become independent
377
+
* from who originally issued it.
378
+
*/
379
+
ops = rcu_dereference_protected(fence->ops, true);
380
+
if (!ops->release && !ops->wait)
381
+
RCU_INIT_POINTER(fence->ops, NULL);
374
382
375
383
/* Stash the cb_list before replacing it with the timestamp */
376
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list_replace(&fence->cb_list, &cb_list);
···
547
537
rcu_read_lock();
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ops = rcu_dereference(fence->ops);
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trace_dma_fence_wait_start(fence);
550
-
if (ops->wait) {
540
+
if (ops && ops->wait) {
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541
/*
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* Implementing the wait ops is deprecated and not supported for
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543
* issuers of fences who need their lifetime to be independent
···
613
603
}
614
604
615
605
ops = rcu_dereference(fence->ops);
616
-
if (ops->release)
606
+
if (ops && ops->release)
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ops->release(fence);
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608
else
619
609
dma_fence_free(fence);
···
649
639
650
640
rcu_read_lock();
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641
ops = rcu_dereference(fence->ops);
652
-
if (!was_set && ops->enable_signaling) {
642
+
if (!was_set && ops && ops->enable_signaling) {
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trace_dma_fence_enable_signal(fence);
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644
655
645
if (!ops->enable_signaling(fence)) {
···
1035
1025
1036
1026
rcu_read_lock();
1037
1027
ops = rcu_dereference(fence->ops);
1038
-
if (ops->set_deadline && !dma_fence_is_signaled(fence))
1028
+
if (ops && ops->set_deadline && !dma_fence_is_signaled(fence))
1039
1029
ops->set_deadline(fence, deadline);
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1030
rcu_read_unlock();
1041
1031
}
+2
-2
include/linux/dma-fence.h
+2
-2
include/linux/dma-fence.h
···
472
472
473
473
rcu_read_lock();
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ops = rcu_dereference(fence->ops);
475
-
if (ops->signaled && ops->signaled(fence)) {
475
+
if (ops && ops->signaled && ops->signaled(fence)) {
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476
rcu_read_unlock();
477
477
dma_fence_signal_locked(fence);
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478
return true;
···
508
508
509
509
rcu_read_lock();
510
510
ops = rcu_dereference(fence->ops);
511
-
if (ops->signaled && ops->signaled(fence)) {
511
+
if (ops && ops->signaled && ops->signaled(fence)) {
512
512
rcu_read_unlock();
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513
dma_fence_signal(fence);
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514
return true;