Re: Bad behavior by rdma-core ?

Bob Pearson
2021-10-14T16:15:04Z

On 10/14/21 9:57 AM, Bob Pearson wrote:
> I have been chasing a bug in the rxe driver seen in the python tests (test_cq_events_ud).
> The following occurs
>
> The first time I execute this test it creates two AHs which are allocated by
> rdma-core and passed to rxe_create_ah. The test attempts to destroy them
> (i.e. rxe_destroy_ah is called in the provider driver) but rdma-core does not
> destroy them (i.e. rxe_destroy_ah is not called in the kernel).
>
> The rxe driver saves the AV state and some metadata for these AHs and keeps it
> since it thinks they are still active.
>
> The second or third time I execute this test two new AHs are created by
> rxe_create_ah but the memory passed in from rdma-core is the same as the first
> test. I.e. it has recycled them but they are still active in the driver so
> the result is chaos.
>
> Somehow rdma-core thinks it has destroyed the AHs but it does not call down to the
> driver. This only occurs for AHs AFAIK.
>
> Bob
>

The cause seems simple enough.

In uverbs_cmd.c ib_uverbs_create_ah() calls rdma_create_user_ah() which
eventually calls device->ops.create_user_ah() or device->ops.create_ah().

But ib_uverbs_destroy_ah does *not* call rdma_uverbs_destroy_ah() it just
deletes the object.