Re: [PATCH v7 0/8] Introduce 'yank' oob qmp command to recover from hanging qemu

[Lukas Straub]

On Tue, 4 Aug 2020 10:11:22 +0200
Lukas Straub <lukasstraub2@web.de> wrote:

> Hello Everyone,
> In many cases, if qemu has a network connection (qmp, migration, chardev, 
> etc.)
> to some other server and that server dies or hangs, qemu hangs too.
> These patches introduce the new 'yank' out-of-band qmp command to recover from
> these kinds of hangs. The different subsystems register callbacks which get
> executed with the yank command. For example the callback can shutdown() a
> socket. This is intended for the colo use-case, but it can be used for other
> things too of course.
> 
> Regards,
> Lukas Straub
> 
> v7:
>  -yank_register_instance now returns error via Error **errp instead of 
> aborting
>  -dropped "chardev/char.c: Check for duplicate id before  creating chardev"
> 
> v6:
>  -add Reviewed-by and Acked-by tags
>  -rebase on master
>  -lots of changes in nbd due to rebase
>  -only take maintainership of util/yank.c and include/qemu/yank.h (Daniel P. 
> Berrangé)
>  -fix a crash discovered by the newly added chardev test
>  -fix the test itself
> 
> v5:
>  -move yank.c to util/
>  -move yank.h to include/qemu/
>  -add license to yank.h
>  -use const char*
>  -nbd: use atomic_store_release and atomic_load_aqcuire
>  -io-channel: ensure thread-safety and document it
>  -add myself as maintainer for yank
> 
> v4:
>  -fix build errors...
> 
> v3:
>  -don't touch softmmu/vl.c, use __contructor__ attribute instead (Paolo 
> Bonzini)
>  -fix build errors
>  -rewrite migration patch so it actually passes all tests
> 
> v2:
>  -don't touch io/ code anymore
>  -always register yank functions
>  -'yank' now takes a list of instances to yank
>  -'query-yank' returns a list of yankable instances
> 
> Lukas Straub (8):
>   Introduce yank feature
>   block/nbd.c: Add yank feature
>   chardev/char-socket.c: Add yank feature
>   migration: Add yank feature
>   io/channel-tls.c: make qio_channel_tls_shutdown thread-safe
>   io: Document thread-safety of qio_channel_shutdown
>   MAINTAINERS: Add myself as maintainer for yank feature
>   tests/test-char.c: Wait for the chardev to connect in
>     char_socket_client_dupid_test
> 
>  MAINTAINERS                   |   6 ++
>  block/nbd.c                   | 129 +++++++++++++++---------
>  chardev/char-socket.c         |  31 ++++++
>  include/io/channel.h          |   2 +
>  include/qemu/yank.h           |  80 +++++++++++++++
>  io/channel-tls.c              |   6 +-
>  migration/channel.c           |  12 +++
>  migration/migration.c         |  25 ++++-
>  migration/multifd.c           |  10 ++
>  migration/qemu-file-channel.c |   6 ++
>  migration/savevm.c            |   6 ++
>  qapi/misc.json                |  45 +++++++++
>  tests/Makefile.include        |   2 +-
>  tests/test-char.c             |   1 +
>  util/Makefile.objs            |   1 +
>  util/yank.c                   | 184 ++++++++++++++++++++++++++++++++++
>  16 files changed, 493 insertions(+), 53 deletions(-)
>  create mode 100644 include/qemu/yank.h
>  create mode 100644 util/yank.c
> 
> --
> 2.20.1

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