Re: netdev-socket test hang (s390 host, mips64el guest, backtrace)

[Peter Maydell]

On Thu, 13 Apr 2023 at 11:50, Peter Maydell <peter.maydell@linaro.org> wrote:
>
> I just found a hung netdev-socket test on our s390 CI runner.
> Looks like a deadlock, no processes using CPU.
> Here's the backtrace; looks like both QEMU processes are sat
> idle but the test process is sat waiting forever for something
> in test_stream_inet_reconnect(). Any ideas?

May well not be related, but I think there's a race condition
in this test's inet_get_free_port() code. The code tries
to find a free port number by creating a socket, looking
at what port it is bound to, and then closing the socket.
If there are several copies of this test running at once
(as is plausible in a 'make -j8' setup), then you can
get an interleaving:

 test 1                       test 2
   find a port number
   close the socket
                              find a port number
                              (get the same number as test 1)
                              close the socket
   use port number for test
                              use port number for test
                              (fail because of test 1)


thanks
-- PMM