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    Subject[PATCH 3.16 089/305] IB/cm: Fix sleeping while spin lock is held
    3.16.63-rc1 review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Parav Pandit <parav@mellanox.com>

    commit 33f93e1ebcf5acfaef06cda2d3e373730519e33e upstream.

    In case of LAP are used for RoCE, it can lead to a problem of sleeping a
    context while spin lock is held in below flow.

    cm_lap_handler
    ->spin_lock
    -> <..switch_case..>
    -> cm_init_av_for_response
    -> ib_init_ah_from_wc
    -> rdma_addr_find_l2_eth_by_grh
    wait_for_completion()

    Therefore ah attribute initialization is done for incoming lap requests
    outside of the lock context.

    Signed-off-by: Parav Pandit <parav@mellanox.com>
    Reviewed-by: Daniel Jurgens <danielj@mellanox.com>
    Signed-off-by: Leon Romanovsky <leon@kernel.org>
    Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
    Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
    ---
    drivers/infiniband/core/cm.c | 11 ++++++-----
    1 file changed, 6 insertions(+), 5 deletions(-)

    --- a/drivers/infiniband/core/cm.c
    +++ b/drivers/infiniband/core/cm.c
    @@ -2770,6 +2770,12 @@ static int cm_lap_handler(struct cm_work
    if (!cm_id_priv)
    return -EINVAL;

    + ret = cm_init_av_for_response(work->port, work->mad_recv_wc->wc,
    + work->mad_recv_wc->recv_buf.grh,
    + &cm_id_priv->av);
    + if (ret)
    + goto deref;
    +
    param = &work->cm_event.param.lap_rcvd;
    param->alternate_path = &work->path[0];
    cm_format_path_from_lap(cm_id_priv, param->alternate_path, lap_msg);
    @@ -2809,11 +2815,6 @@ static int cm_lap_handler(struct cm_work

    cm_id_priv->id.lap_state = IB_CM_LAP_RCVD;
    cm_id_priv->tid = lap_msg->hdr.tid;
    - ret = cm_init_av_for_response(work->port, work->mad_recv_wc->wc,
    - work->mad_recv_wc->recv_buf.grh,
    - &cm_id_priv->av);
    - if (ret)
    - goto unlock;
    cm_init_av_by_path(param->alternate_path, &cm_id_priv->alt_av,
    cm_id_priv);
    ret = atomic_inc_and_test(&cm_id_priv->work_count);
    \
     
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