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Date:      Tue, 5 May 2020 00:22:23 +0000
From:      "Reynolds, Paul" <paul.reynolds@redcom.com>
To:        "freebsd-transport@freebsd.org" <freebsd-transport@freebsd.org>
Subject:   SCTP deadlock
Message-ID:  <112525e87fce467e97f1d455ef9bf685@redcom.com>

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Hi,


My apologies if this is not the right mailing list for this question. I am =
hoping to get some suggestions on how to debug an sctp issue I have been ha=
ving.


I have a set of programs that use sctp for communication. For now these pro=
cesses are all running on the same machine. They are using SEQPACKET mode t=
o send messages back and forth. Each process has multiple threads, but only=
 one socket. The threads are mutex protected such that the socket cannot be=
 accessed by more than one thread at a time. Very occasionally one of the s=
ockets will become permanently blocked on an sctp send or receive call and =
I am trying to figure out why. In the cases where it has become blocked on =
a send call, the corresponding receive process is not blocked and can send/=
receive data to other destinations. These processes can run fine for months=
 and then suddenly run into this problem. I have been able to reproduce thi=
s once or twice by subjecting the system to unrealistically high levels of =
traffic, but it still takes several days or more to reproduce the problem. =
I now have a system that is stuck in this mode and am trying to gather as m=
uch information as possible.


How should I go about debugging this? The output of sockstat and netstat ha=
ve not been very helpful up to this point.


Thanks for any help you might be able to provide,

Paul



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