oob/v2.0.x/msg drop #2478
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oob/v2.0.x/msg drop #2478
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The problem was observed for direct modex used with recursive doubling algorithm (used for collective ID calculation prior to d52a2d0) that has pairwise nature and counter-connections are highly likely. The following scenario was uncovering the issue: * ranks `x` and `y` want to communicate with each other, `x` < `y`; * rank `x` initiates the connection and sends the ack; * rank `y` starts to `connect()` and gets the ack from `x`; * `y` identifies that it already started connecting and `y` > `x` so it rejects incoming connection. * `x` sees that his connection was rejected in `mca_oob_tcp_peer_recv_connect_ack()` when trying to read the message header using `tcp_peer_recv_blocking()` which calls `mca_oob_tcp_peer_close()` that effectively flushes all the messages in the peer->send_queue. * `y` send the ack to `x` and the connection is established, however all the messages for the peer at `x` are vanished (except the front one in peer->send_msg). This commit introduces a "nack" function that will be used at `y` side to tell `x` that `y` has the priority and `x`'s connection should be closed. This allows to avoid "guessing" on the unexpectedly closed connection. (cherry-picked from ada93e0) Signed-off-by: Artem Polyakov <artpol84@gmail.com>
(cherry-picked from 30ff8be) Signed-off-by: Artem Polyakov <artpol84@gmail.com>
Plug coverity defect CID 1396541. (cherry-picked from bf79e83) Signed-off-by: Artem Polyakov <artpol84@gmail.com>
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Contributor
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@jjhursey if I go by the link I see that test has passed. Can you check please? |
Contributor
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bot:ibm:retest |
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@rhc54 Can you review? Thanks. |
rhc54
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Dec 2, 2016
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@hppritcha Good to go. |
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