Re: [PATCH v2 1/1] util/async-teardown: wire up query-command-line-options

[Markus Armbruster <armbru@redhat.com>]

Thomas Huth <thuth@redhat.com> writes:

> On 20/03/2023 16.31, Markus Armbruster wrote:
>> Claudio Imbrenda <imbrenda@linux.ibm.com> writes:
>> 
>>> 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.
>> 
>> There was nothing improper in its wiring.  The issue is that
>> query-command-line-options is junk.  See my recent post
>> 
>>      Subject: query-command-line-options (was: [PATCH 1/7] qemu: capabilities: Introduce QEMU_CAPS_MACHINE_ACPI)
>>      Date: Tue, 07 Mar 2023 10:40:23 +0100
>>      Message-ID: <87jzzsc320.fsf_-_@pond.sub.org>
>> 
>>> 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>
>>> ---
>>>   util/async-teardown.c | 17 +++++++++++++++++
>>>   1 file changed, 17 insertions(+)
>>>
>>> diff --git a/util/async-teardown.c b/util/async-teardown.c
>>> index 62cdeb0f20..c9b9a3cdb2 100644
>>> --- a/util/async-teardown.c
>>> +++ b/util/async-teardown.c
>>> @@ -12,6 +12,9 @@
>>>    */
>>>   
>>>   #include "qemu/osdep.h"
>>> +#include "qemu/config-file.h"
>>> +#include "qemu/option.h"
>>> +#include "qemu/module.h"
>>>   #include <dirent.h>
>>>   #include <sys/prctl.h>
>>>   #include <sched.h>
>>> @@ -144,3 +147,17 @@ void init_async_teardown(void)
>>>       clone(async_teardown_fn, new_stack_for_clone(), CLONE_VM, NULL);
>>>       sigprocmask(SIG_SETMASK, &old_signals, NULL);
>>>   }
>>> +
>>> +static QemuOptsList qemu_async_teardown_opts = {
>>> +    .name = "async-teardown",
>>> +    .head = QTAILQ_HEAD_INITIALIZER(qemu_async_teardown_opts.head),
>>> +    .desc = {
>>> +        { /* end of list */ }
>>> +    },
>>> +};
>>> +
>>> +static void register_async_teardown(void)
>>> +{
>>> +    qemu_add_opts(&qemu_async_teardown_opts);
>>> +}
>>> +opts_init(register_async_teardown);
>> 
>> Now it *is* improperly wired up :)
>> 
>> You're defining new QemuOpts config group "async-teardown" with
>> arbitrary option parameters, but don't actually use it for parsing or
>> recording the option.  I figure because you can't: there is no option
>> argument to parse and record, which is what QemuOpts is designed to do.
>> 
>> If you need the feature to be visible in query-command-line-options, you
>> should make it an option parameter (a KEY, not a GROUP), preferably of
>> an existing group / option.
>
> Would it make sense to add it e.g. to "-action" instead, i.e. something like 
> "-action teardown=async" ?

I believe the new parameter "teardown" would be visible in
query-command-line-options.

How well does it fit -action?