Re: [Qemu-devel] [PATCH v2 00/16] chardev: refactoring & many bugfixes related tcp_chr_wait_connected

[Marc-André Lureau]

Hi
On Wed, Jan 23, 2019 at 6:27 PM Daniel P. Berrangé <address@hidden> wrote:
>
> This is a followup to
>
>   v1: https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg03344.html
>
> This series comes out of a discussion between myself & Yongji Xie in:
>
>   https://lists.gnu.org/archive/html/qemu-devel/2019-01/msg01881.html
>
> I eventually understood that the problem faced was that
> tcp_chr_wait_connected was racing with the background connection attempt
> previously started, causing two connections to be established. This
> broke because some vhost user servers only allow a single connection.
>
> After messing around with the code alot the final solution was in fact
> very easy. We simply have to delay the first background connection
> attempt until the main loop is running. It will then automatically
> turn into a no-op if tcp_chr_wait_connected has been run. This is
> dealt with in the last patch in this series
>
> I believe this should solve the problem Yongji Xie faced, and thus not
> require us to add support for "nowait" option with client sockets at
> all. The reconnect=1 option effectively already implements nowait
> semantics, and now plays nicely with tcp_chr_wait_connected.
>
> In investigating this I found various other bugs that needed fixing and
> identified some useful refactoring to simplify / clarify the code, hence
> this very long series.
>
> This series passes make check-unit & check-qtest (for x86_64 target).
>
> I did a test with tests/vhost-user-bridge too, which was in fact already
> broken for the same reason Yongji Xie found - it only accepts a single
> connection. This series fixes use of reconnect=1 with vhost-user-bridge.
>
> Changed in v2:
>
>  - Rewrite the way we synchronize in tcp_chr_wait_connected again
>    to cope with chardev+device hotplug scenario
>  - Add extensive unit test coverage
>  - Resolve conflicts with git master
>
> Daniel P. Berrangé (16):
>   io: store reference to thread information in the QIOTask struct
>   io: add qio_task_wait_thread to join with a background thread
>   chardev: fix validation of options for QMP created chardevs
>   chardev: forbid 'reconnect' option with server sockets
>   chardev: forbid 'wait' option with client sockets
>   chardev: remove many local variables in qemu_chr_parse_socket
>   chardev: ensure qemu_chr_parse_compat reports missing driver error
>   chardev: remove unused 'sioc' variable & cleanup paths
>   chardev: split tcp_chr_wait_connected into two methods
>   chardev: split up qmp_chardev_open_socket connection code
>   chardev: use a state machine for socket connection state
>   chardev: honour the reconnect setting in tcp_chr_wait_connected
>   chardev: disallow TLS/telnet/websocket with tcp_chr_wait_connected
>   chardev: fix race with client connections in tcp_chr_wait_connected
>   tests: expand coverage of socket chardev test
>   chardev: ensure termios is fully initialized
>
>  chardev/char-serial.c          |   2 +-
>  chardev/char-socket.c          | 487 ++++++++++++++++++-------
>  chardev/char.c                 |   2 +
>  include/io/task.h              |  29 +-
>  io/task.c                      |  88 +++--
>  io/trace-events                |   2 +
>  tests/ivshmem-test.c           |   2 +-
>  tests/libqtest.c               |   4 +-
>  tests/test-char.c              | 643 ++++++++++++++++++++++++---------
>  tests/test-filter-redirector.c |   4 +-
>  10 files changed, 928 insertions(+), 335 deletions(-)
>

With the fix squashed, I am queuing this series.
Reviewed-by: Marc-André Lureau <address@hidden>


> --
> 2.20.1
>