What really happens when a connection race happens?

What really happens when a connection race happens?

[xxhdx1985126]

Hi, everyone.

I'm reading the source code of Pipe in ceph, and I'm confused about the code for connection race processing. Suppose that the policy the two Pipe involved is lossless_peer, one of them wins and send the other pipe a CEPH_MSGR_TAG_WAIT message which makes the other Pipe's writer to cond.wait(), and then the winning pipe goes back to waiting for a ceph_msg_connect message to come. But, under this circumstance, the writer of the other pipe is waiting, and as far as I know,  unless something happens it will never send ceph_msg_connect messages, so they will wait for each other for ever........  There must be some misunderstanding here, but I don't know where, please help me. Thank you:-)

Re: What really happens when a connection race happens?

[Gregory Farnum]

On Sun, Dec 25, 2016 at 2:31 AM, xxhdx1985126 <xxhdx1985126@163.com> wrote:
> Hi, everyone.
>
> I'm reading the source code of Pipe in ceph, and I'm confused about the code for connection race processing. Suppose that the policy the two Pipe involved is lossless_peer, one of them wins and send the other pipe a CEPH_MSGR_TAG_WAIT message which makes the other Pipe's writer to cond.wait(), and then the winning pipe goes back to waiting for a ceph_msg_connect message to come. But, under this circumstance, the writer of the other pipe is waiting, and as far as I know,  unless something happens it will never send ceph_msg_connect messages, so they will wait for each other for ever........  There must be some misunderstanding here, but I don't know where, please help me. Thank you:-)

The point is that we have racing connect attempts here — the "winner"
has already sent out a connection attempt which the loser will respond
to. So neither of them needs to do anything; when the loser processes
the winner's connection attempt, it will shut down its losing Pipe,
start up a Pipe with the incoming attempt, and send back an
acknowledgement to the winner.
-Greg