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

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Fri, 24 Mar 2023 18:56:06 +0100
Thomas Huth <thuth@redhat.com> wrote:

> 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 

both are fine for me (although I have a slight preference for removing
it altogether)

> two releases.
> 
>   Thomas
>