Re: [PATCH v2 0/2] iwarp device removal deadlock fixes

[Doug Ledford <dledford-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

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On Fri, 2016-07-29 at 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-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
              GPG KeyID: 0E572FDD

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