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Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands
From: |
Kevin Wolf |
Subject: |
Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands |
Date: |
Fri, 17 Jan 2020 10:40:50 +0100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
Am 17.01.2020 um 08:57 hat Markus Armbruster geschrieben:
> Kevin Wolf <address@hidden> writes:
>
> > Am 16.01.2020 um 14:00 hat Markus Armbruster geschrieben:
> >> Kevin Wolf <address@hidden> writes:
> >> > I have no idea if we will eventually get a case where the command wants
> >> > to behave different between the two modes and actually has use for a
> >> > coroutine. I hope not.
> >> >
> >> > But using two bools rather than a single enum keeps the code simple and
> >> > leaves us all options open if it turns out that we do have a use case.
> >>
> >> I can buy the argument "the two are conceptually orthogonal, although we
> >> don't haven't found a use for one of the four cases".
> >>
> >> Let's review the four combinations of the two flags once more:
> >>
> >> * allow-oob: false, coroutine: false
> >>
> >> Handler runs in main loop, outside coroutine context. Okay.
> >>
> >> * allow-oob: false, coroutine: true
> >>
> >> Handler runs in main loop, in coroutine context. Okay.
> >>
> >> * allow-oob: true, coroutine: false
> >>
> >> Handler may run in main loop or in iothread, outside coroutine
> >> context. Okay.
> >>
> >> * allow-oob: true, coroutine: true
> >>
> >> Handler may run (in main loop, in coroutine context) or (in iothread,
> >> outside coroutine context). This "in coroutine context only with
> >> execute, not with exec-oob" behavior is a bit surprising.
> >>
> >> We could document it, noting that it may change to always run in
> >> coroutine context. Or we simply reject this case as "not
> >> implemented". Since we have no uses, I'm leaning towards reject. One
> >> fewer case to test then.
> >
> > What would be the right mode of rejecting it?
> >
> > I assume we should catch it somewhere in the QAPI generator (where?) and
>
> check_flags() in expr.py?
Looks like the right place, thanks.
> > then just assert in the C code that both flags aren't set at the same
> > time?
>
> I think you already do, in do_qmp_dispatch():
>
> assert(!(oob && qemu_in_coroutine()));
>
> Not sure that's the best spot. Let's see when I review PATCH 3.
This asserts that exec-oob handlers aren't executed in coroutine
context. It doesn't assert that the handler doesn't have QCO_COROUTINE
and QCO_ALLOW_OOB set at the same time.
> >> >> > @@ -194,8 +195,9 @@ out:
> >> >> > return ret
> >> >> >
> >> >> >
> >> >> > -def gen_register_command(name, success_response, allow_oob,
> >> >> > allow_preconfig):
> >> >> > - options = []
> >> >> > +def gen_register_command(name: str, success_response: bool,
> >> >> > allow_oob: bool,
> >> >> > + allow_preconfig: bool, coroutine: bool) ->
> >> >> > str:
> >> >> > + options = [] # type: List[str]
> >>
> >> One more: this is a PEP 484 type hint. With Python 3, we can use PEP
> >> 526 instead:
> >>
> >> options: List[str] = []
> >>
> >> I think we should.
> >
> > This requires Python 3.6, unfortunately. The minimum requirement for
> > building QEMU is 3.5.
>
> *Sigh*
One of the reasons why I would have preferred 3.6 as the minimum, but
our policy says that Debian oldstabe is still relevant for another two
years. *shrug*
Kevin
- [PATCH v3 0/4] qmp: Optionally run handlers in coroutines, Kevin Wolf, 2020/01/15
- [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Kevin Wolf, 2020/01/15
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Markus Armbruster, 2020/01/15
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Kevin Wolf, 2020/01/15
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Markus Armbruster, 2020/01/16
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Kevin Wolf, 2020/01/16
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Markus Armbruster, 2020/01/17
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands,
Kevin Wolf <=
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Markus Armbruster, 2020/01/17
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Kevin Wolf, 2020/01/17
- Re: [PATCH v3 1/4] qapi: Add a 'coroutine' flag for commands, Markus Armbruster, 2020/01/17
[PATCH v3 2/4] vl: Initialise main loop earlier, Kevin Wolf, 2020/01/15
[PATCH v3 4/4] block: Mark 'block_resize' as coroutine, Kevin Wolf, 2020/01/15