[openib-general] [RFC] [PATCH] IB/uverbs: Don't serialize with ib_uverbs_idr_mutex

[Roland Dreier]

    Michael> Won't this let the user issue multiple modify QP commands
    Michael> in parallel on the same QP? mthca at least does not
    Michael> protect against such attempts, and doing this will
    Michael> confuse the hardware.

Hmm, that's a good point.  But I did write the following in
Documentation/infiniband/core_locking.txt:

  All of the methods in struct ib_device exported by a low-level
  driver must be fully reentrant.  The low-level driver is required to
  perform all synchronization necessary to maintain consistency, even
  if multiple function calls using the same object are run
  simultaneously.

  The IB midlayer does not perform any serialization of function calls.

So I guess this is a bug in mthca.

I think modify_srq at least has the same problem.  I'll audit this and
fix it up in mthca.

 - R.