On Fri, 2016-07-29@13:36 -0700, Steve Wise wrote:

This series fixes the deadlock issue discovered while testing
nvmf/rdma
handling rdma device removal events from the rdma_cm.??For a
discussion
of the deadlock that can happen, see

http://lists.infradead.org/pipermail/linux-nvme/2016-July/005440.html
.

For my description of the deadlock itself, see this post in the above
thread:

http://lists.infradead.org/pipermail/linux-nvme/2016-July/005465.html

In a nutshell, iw_cxgb4 and the iw_cm block during qp/cm_id
destruction
until all references are removed.??This combined with the iwarp CM
passing
disconnect events up to the rdma_cm during disconnect and/or qp/cm_id
destruction
leads to a deadlock.

My proposed solution is to remove the need for iw_cxgb4 and iw_cm to
block during object destruction for the refnts to reach 0, but rather
to
let the freeing of the object memory be deferred when the last deref
is
done, which is SOP in the much of the linux kernel. This allows all
the
qps/cm_ids to be destroyed without blocking, and all the object
memory
freeing ends up happinging when the application's device_remove event
handler function returns to the rdma_cm.

This series is needed along with Sagi's fixes from:
https://www.spinics.net/lists/linux-rdma/msg38715.html

Hey Faisal, it would be great to get some review/test tags from Intel
on the iw_cm change.??Thanks!

Changes since v1:

- reworded commit text for the iw_cm patch

- added a iw_cm_id flag to drop pending events when the cm_id has
been marked for destruction.

---

Steve Wise (2):
? iw_cxgb4: don't block in destroy_qp awaiting the last deref
? iw_cm: free cm_id resources on the last deref

?drivers/infiniband/core/iwcm.c?????????| 54 +++++++++++-------------
----------
?drivers/infiniband/core/iwcm.h?????????|??2 +-
?drivers/infiniband/hw/cxgb4/iw_cxgb4.h |??2 +-
?drivers/infiniband/hw/cxgb4/qp.c???????| 21 ++++++++-----
?4 files changed, 33 insertions(+), 46 deletions(-)

Series applied, thanks.

-- 
Doug Ledford <dledford at redhat.com>
              GPG KeyID: 0E572FDD
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