On 11/07/2016 08:55 AM, Christian König wrote:
Am 07.11.2016 um 04:29 schrieb Michel Dänzer:
On 07/11/16 11:47 AM, Mario Kleiner wrote:
External clients which import our bo's wait only
for exclusive dmabuf-fences, not on shared ones,
so attach fences on exported buffers as exclusive
ones, if the buffers get imported by an external
client.
See discussion in thread:
https://lists.freedesktop.org/archives/dri-devel/2016-October/122370.html
Tested on Intel iGPU + AMD Tonga dGPU as DRI3/Present
Prime render offload, and with the Tonga standalone as
primary gpu.
v2: Add a wait for all shared fences before prime export,
as suggested by Christian Koenig.
v3: - Mark buffer prime_exported in amdgpu_gem_prime_pin,
so we only use the exclusive fence when exporting a
bo to external clients like a separate iGPU, but not
when exporting/importing from/to ourselves as part of
regular DRI3 fd passing.
- Propagate failure of reservation_object_wait_rcu back
to caller.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95472
(v1) Tested-by: Mike Lothian <mike@xxxxxxxxxxxxxx>
FWIW, I think the (v1) is usually added at the end of the line, not at
the beginning.
Ok.
[...]
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
index 7700dc2..c4494d0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
@@ -81,6 +81,20 @@ int amdgpu_gem_prime_pin(struct drm_gem_object *obj)
{
struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
int ret = 0;
+ long lret;
+
+ /*
+ * Wait for all shared fences to complete before we switch to
future
+ * use of exclusive fence on this prime_exported bo.
+ */
+ lret = reservation_object_wait_timeout_rcu(bo->tbo.resv, true,
false,
+ MAX_SCHEDULE_TIMEOUT);
+ if (unlikely(lret < 0)) {
+ DRM_DEBUG_PRIME("Fence wait failed: %li\n", lret);
+ return lret;
+ }
+
+ bo->prime_exported = true;
We should probably clear bo->prime_exported in amdgpu_gem_prime_unpin.
Also, I think we should set bo->prime_exported (prime_shared?) in
amdgpu_gem_prime_import_sg_table as well, so that we'll also set
exclusive fences on BOs imported from other GPUs.
Yes, really good idea.
Ok. I guess we don't need to wait for fences there before setting the
flag/counter, as we can't have done anything yet with the bo just
created from the imported sg_table?
Additional to that are we sure that amdgpu_gem_prime_pin() is only
called once for each GEM object? Could in theory be that somebody
exports a BO to another GFX device as well as a V4L device for example.
In this case we would need a counter, but I need to double check that as
well.
If we want to clear the prime_exported flag in amdgpu_gem_prime_unpin()
as an optimization if all clients detach from the buffer, then we need a
prime_shared_counter instead of a prime_exported flag afaics. The dmabuf
api allows multiple clients to import and attach to an exported dmabuf,
each one calling dma_buf_attach which will call amdgpu_gem_prime_pin.
In general I would protected the flag/counter by the BO being reserved
to avoid any races. In other word move those lines a bit down after the
amdgpu_bo_reserve().
Ok.
-mario
Regards,
Christian.
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