Bug#935980: jackd2: Segfaults when qjackctl patchbay is activated

[Christopher David Howie]

On 8/28/2019 12:29 PM, Christopher David Howie wrote:
> jackd segfaults whenever the qjackctl patchbay is activated with a
> non-empty set of patches.  It's not clear to me exactly why this
> happens, but it happens every time.

I have done some additional testing on this and wanted to share the
results.  First, let me elaborate on my setup as some aspects may be
relevant to the problem.

* The network master is running jackd2 1.9.11 on Windows 10.

* The network slave is running jackd2 1.9.12 on Debian Buster (using the
provided Debian packages).

* There is a qjackctl patchbay on the network master that patches all
local output ports to the slave's network input ports, and the slave's
network output ports to the local input ports.

* There is a qjackctl patchbay on the network slave that patches various
ports between the slave's local ports and Ardour.

The bug is not 100% reproducible but it happens way more often than not
(probably in the 90%+ range) and appears to be triggered by both
patchbays being active (or, rather, all of the resulting port patches
being made).

If I restart everything and only active one of the patchbays (it does
not matter which one) then the the slave jackd does not segfault.
_Immediately_ upon activating the other patchbay, the slave jackd will
almost certainly segfault.

I have downgraded my jackd packages on the slave (jackd2,
libjack-jackd2-0, and libjack-jackd2-dev) to their respective latest
versions in stretch, which downgrades jackd from 1.9.12 (buster) to
1.9.10 (stretch).  This fully resolves the problem, hinting that this
segfault is a regression that was added after 1.9.10.

(Side note: Bernhard's issue looks unrelated and I'm not sure why it was
added as a reply to my report.)

-- 
Chris Howie
http://www.chrishowie.com
http://en.wikipedia.org/wiki/User:Crazycomputers

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