Am 08.06.23 um 16:30 schrieb Tvrtko Ursulin:
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
For dma_fence_is_signaled signaling critical path annotations are an
annoying cause of false positives when using dma_fence_is_signaled and
indirectly higher level helpers such as dma_resv_test_signaled etc.
Drop the critical path annotation since the "is signaled" API does not
guarantee to ever change the signaled status anyway.
We do that by adding a low level _dma_fence_signal helper and use it from
dma_fence_is_signaled.
I have been considering dropping the signaling from the
dma_fence_is_signaled() function altogether.
Doing this together with the spin locking we have in the dma_fence is
just utterly nonsense since the purpose of the external spinlock is to
keep the signaling in order while this here defeats that.
The quick check is ok I think, but signaling the dma_fence and issuing
the callbacks should always come from the interrupt handler.
Christian.
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Cc: Christian König <christian.koenig@xxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/dma-buf/dma-fence.c | 26 ++++++++++++++++++++------
include/linux/dma-fence.h | 3 ++-
2 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index f177c56269bb..ace1415f0566 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -444,6 +444,25 @@ int dma_fence_signal_locked(struct dma_fence *fence)
}
EXPORT_SYMBOL(dma_fence_signal_locked);
+/**
+ * __dma_fence_signal - signal completion of a fence bypassing critical section annotation
+ * @fence: the fence to signal
+ *
+ * This low-level helper should not be used by code external to dma-fence.h|c!
+ */
+int _dma_fence_signal(struct dma_fence *fence)
+{
+ unsigned long flags;
+ int ret;
+
+ spin_lock_irqsave(fence->lock, flags);
+ ret = dma_fence_signal_timestamp_locked(fence, ktime_get());
+ spin_unlock_irqrestore(fence->lock, flags);
+
+ return ret;
+}
+EXPORT_SYMBOL(_dma_fence_signal);
+
/**
* dma_fence_signal - signal completion of a fence
* @fence: the fence to signal
@@ -459,7 +478,6 @@ EXPORT_SYMBOL(dma_fence_signal_locked);
*/
int dma_fence_signal(struct dma_fence *fence)
{
- unsigned long flags;
int ret;
bool tmp;
@@ -467,11 +485,7 @@ int dma_fence_signal(struct dma_fence *fence)
return -EINVAL;
tmp = dma_fence_begin_signalling();
-
- spin_lock_irqsave(fence->lock, flags);
- ret = dma_fence_signal_timestamp_locked(fence, ktime_get());
- spin_unlock_irqrestore(fence->lock, flags);
-
+ ret = _dma_fence_signal(fence);
dma_fence_end_signalling(tmp);
return ret;
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index d54b595a0fe0..d94768ad70e4 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -387,6 +387,7 @@ static inline void dma_fence_end_signalling(bool cookie) {}
static inline void __dma_fence_might_wait(void) {}
#endif
+int _dma_fence_signal(struct dma_fence *fence);
int dma_fence_signal(struct dma_fence *fence);
int dma_fence_signal_locked(struct dma_fence *fence);
int dma_fence_signal_timestamp(struct dma_fence *fence, ktime_t timestamp);
@@ -452,7 +453,7 @@ dma_fence_is_signaled(struct dma_fence *fence)
return true;
if (fence->ops->signaled && fence->ops->signaled(fence)) {
- dma_fence_signal(fence);
+ _dma_fence_signal(fence);
return true;
}
