Re: [PATCH v3 1/1] util/async-teardown: wire up query-command-line-options

[Thomas Huth <thuth@redhat.com>]

On 24/03/2023 18.45, Claudio Imbrenda wrote:
> The recently introduced -async-teardown commandline option was not
> wired up properly and did not show up in the output of the QMP command
> query-command-line-options. This means that libvirt will have no way to
> discover whether the feature is supported.
> 
> This patch fixes the issue by correctly wiring up the commandline
> option so that it appears in the output of query-command-line-options.
> 
> Reported-by: Boris Fiuczynski <fiuczy@linux.ibm.com>
> Fixes: c891c24b1a ("os-posix: asynchronous teardown for shutdown on Linux")
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> ---
>   os-posix.c            | 14 ++++++++++++++
>   qemu-options.hx       | 35 ++++++++++++++++++++++++-----------
>   util/async-teardown.c | 21 +++++++++++++++++++++
>   3 files changed, 59 insertions(+), 11 deletions(-)
> 
> diff --git a/os-posix.c b/os-posix.c
> index 5adc69f560..48acd7acf5 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -36,6 +36,8 @@
>   #include "qemu/log.h"
>   #include "sysemu/runstate.h"
>   #include "qemu/cutils.h"
> +#include "qemu/config-file.h"
> +#include "qemu/option.h"
>   
>   #ifdef CONFIG_LINUX
>   #include <sys/prctl.h>
> @@ -132,6 +134,8 @@ static bool os_parse_runas_uid_gid(const char *optarg)
>    */
>   int os_parse_cmd_args(int index, const char *optarg)
>   {
> +    QemuOpts *opts;
> +
>       switch (index) {
>       case QEMU_OPTION_runas:
>           user_pwd = getpwnam(optarg);
> @@ -155,6 +159,16 @@ int os_parse_cmd_args(int index, const char *optarg)
>       case QEMU_OPTION_asyncteardown:
>           init_async_teardown();
>           break;
> +    case QEMU_OPTION_teardown:
> +        opts = qemu_opts_parse_noisily(qemu_find_opts("teardown"),
> +                                       optarg, false);
> +        if (!opts) {
> +            return -1;
> +        }
> +        if (qemu_opt_get_bool(opts, "async", false)) {
> +            init_async_teardown();
> +        }
> +        break;
>   #endif
>       default:
>           return -1;
> diff --git a/qemu-options.hx b/qemu-options.hx
> index d42f60fb91..8582980b12 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -4766,20 +4766,33 @@ DEF("qtest-log", HAS_ARG, QEMU_OPTION_qtest_log, "", QEMU_ARCH_ALL)
>   DEF("async-teardown", 0, QEMU_OPTION_asyncteardown,
>       "-async-teardown enable asynchronous teardown\n",
>       QEMU_ARCH_ALL)
> -#endif
>   SRST
>   ``-async-teardown``
> -    Enable asynchronous teardown. A new process called "cleanup/<QEMU_PID>"
> -    will be created at startup sharing the address space with the main qemu
> -    process, using clone. It will wait for the main qemu process to
> -    terminate completely, and then exit.
> -    This allows qemu to terminate very quickly even if the guest was
> -    huge, leaving the teardown of the address space to the cleanup
> -    process. Since the cleanup process shares the same cgroups as the
> -    main qemu process, accounting is performed correctly. This only
> -    works if the cleanup process is not forcefully killed with SIGKILL
> -    before the main qemu process has terminated completely.
> +    Equivalent to -teardown async=on

We should avoid of providing multiple ways of doing the same thing to the 
users if there is no real benefit. So I'd vote for either removing the 
"-async-teardown" option here directly (since it just has been introduced in 
7.2 and there are no known users out there yet), or at least deprecate it 
(put an entry in docs/about/deprecated.rst), so we can remove it again in 
two releases.

  Thomas