Am 03.12.18 um 18:06 schrieb Chris Wilson:
Quoting Christian König (2018-12-03 16:12:14)
Am 03.12.18 um 17:08 schrieb Eric Anholt:
Christian König <ckoenig.leichtzumerken@xxxxxxxxx> writes:
Extract of useful code from the timeline work. This provides a function
to return a stub or dummy fence which is always signaled.
Signed-off-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/dma-buf/dma-fence.c | 36 +++++++++++++++++++++++++++++++++++-
include/linux/dma-fence.h | 1 +
2 files changed, 36 insertions(+), 1 deletion(-)
diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 1551ca7df394..136ec04d683f 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
/*
* fence context counter: each execution context should have its own
* fence context, this allows checking if fences belong to the same
* context or not. One device can have multiple separate contexts,
* and they're used if some engine can run independently of another.
*/
-static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(0);
+static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(1);
What's this change for? I don't see a context allocation in patch #2
where the stub fence is being moved from, so this seems out of place.
The stub fence is using context 0 and seqno 0, but since it is always
signaled this actually shouldn't matter.
So this is just to be on the extra clean side I made sure that nobody
else is using context 0.
I would like to be able to reserve 0 for NO_CONTEXT! The stub being but
one example.
I'm slightly leaning into this direction as well and additional to that
I've already pushed the patches to drm-misc-next.
The only thing we should avoid is to over use 0 as NO_context, e.g. with
complicated sequence numbers or similar.
Christian.
-Chris
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