[erlang-patches] : : More about SCTP and R12B-5

Bjorn Gustavsson <>
Mon Nov 10 12:05:58 CET 2008

On Sat, Nov 8, 2008 at 1:15 PM, Per Hedeland <> wrote:
> Given that writev was introduced by the "original" BSD more than 25
> years ago and is used all over the place in current *BSD (and in the
> Erlang runtime), while kqueue (the "*BSD version" of "kernel poll") is a
> relative newcomer and arguably only needed in "unusual" cases, I would
> say that this has to be qualified as a problem with kqueue, not writev.
> And again I'll claim that the lack of kernel poll is essentially
> uninteresting for many if not most Erlang applications.

We initially thought that the problem only had to do with kqueue, but it turned
out that we could reproduce the problem without using kqueue at all.

Quote from the README file:

"FreeBSD has a bug which cause kqueue/poll/select to fail to detect
that a writev() on a pipe has been made. This bug should have been fixed
in FreeBSD 6.3 and FreeBSD 7.0. More information can be found at:
* http://www.freebsd.org/cgi/cvsweb.cgi/src/sys/kern/sys_pipe.c
* http://lists.freebsd.org/pipermail/freebsd-arch/2007-September/006790.html
NetBSD and DragonFlyBSD probably have or have had the same bug."

>>Not a requirement. But since it sometimes is hard to
>>ensure "trustworthy" and it also is easy to make silly
>>mistakes when applying the patch; having daily builds
>>sure facilitates trying a patch, and maintaining it.
> Very reasonable. So I assume that Jimmy's patches, done against current
> Erlang/OTP code, from someone who has been the tireless maintainer of
> the Erlang FreeBSD port for more than 7 years (the ports *are* built
> daily at freebsd.org btw), will be applied ASAP.:-)

We will have a look at the patches as soon as we have set up a test machine
running FreeBSD. Our goal is to do that before the next release.


Björn Gustavsson, Erlang/OTP, Ericsson AB

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