Re: [PATCH 0/6] net: fix non-deterministic failures of the 'netdev-socket' qtest

[Jason Wang]

On Fri, Jan 5, 2024 at 12:45 AM Stefan Hajnoczi <stefanha@gmail.com> wrote:
>
> On Thu, 4 Jan 2024 at 11:30, Daniel P. Berrangé <berrange@redhat.com> wrote:
> >
> > We've previously bumped up the timeouts in the netdev-socket qtest
> > to supposedly fix non-deterministic failures, however, the failures
> > are still hitting CI.
> >
> > A simple 'listen()' and 'connect()' pairing across 2 QEMU processes
> > should be very quick to execute, even under high system load, so it
> > was never likely that the test was failing due to timeouts being
> > reached.
> >
> > The actual root cause was a race condition in the test design. It
> > was spawning a QEMU with a 'server' netdev, and then spawning one
> > with the 'client' netdev. There was insufficient synchronization,
> > however, so it was possible for the 2nd QEMU process to attempt
> > to 'connect()' before the 'listen()' call was made by the 1st QEMU.
> >
> > In the test scenarios that did not use the 'reconnect' flag, this
> > would result in the client QEMU never getting into the expected
> > state. The test code would thus loop on 'info network' until
> > hitting the maximum wait time.
> >
> > This series reverts the increased timeouts, and fixes synchronization
> > in the test scenarios. It also improves reporting of errors in the
> > socket netdev backend so that 'info network' reports what actually
> > went wrong rather than a useless generic 'connection error' string.
> > This will help us diagnose any future CI problems, should they occurr.
> >
> > Daniel P. Berrangé (6):
> >   Revert "netdev: set timeout depending on loadavg"
> >   Revert "osdep: add getloadavg"
> >   Revert "tests/qtest/netdev-socket: Raise connection timeout to 120
> >     seconds"
> >   net: add explicit info about connecting/listening state
> >   net: handle QIOTask completion to report useful error message
> >   qtest: ensure netdev-socket tests have non-overlapping names
> >
> >  include/qemu/osdep.h        | 10 ---------
> >  meson.build                 |  1 -
> >  net/stream.c                | 18 +++++++++++-----
> >  tests/qtest/netdev-socket.c | 42 +++++++------------------------------
> >  4 files changed, 21 insertions(+), 50 deletions(-)
>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
>

Queued.

Thanks