Re: [PATCH v3 4/4] block: Mark 'block_resize' as coroutine

From: Kevin Wolf <kwolf@redhat.com>
To: Markus Armbruster <armbru@redhat.com>
Cc: stefanha@redhat.com, marcandre.lureau@gmail.com,
	qemu-devel@nongnu.org, qemu-block@nongnu.org
Subject: Re: [PATCH v3 4/4] block: Mark 'block_resize' as coroutine
Date: Thu, 16 Jan 2020 11:13:33 +0100	[thread overview]
Message-ID: <20200116101333.GA9470@linux.fritz.box> (raw)
In-Reply-To: <87tv4vzqd7.fsf@dusky.pond.sub.org>

Am 16.01.2020 um 10:45 hat Markus Armbruster geschrieben:
> Kevin Wolf <kwolf@redhat.com> writes:
> > block_resize is safe to run in a coroutine, so use it as an example for
> > the new 'coroutine': true annotation in the QAPI schema.
> >
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

> > diff --git a/blockdev.c b/blockdev.c
> > index 8e029e9c01..b5e5d1e072 100644
> > --- a/blockdev.c
> > +++ b/blockdev.c
> > @@ -3161,9 +3161,9 @@ void hmp_drive_del(Monitor *mon, const QDict *qdict)
> >      aio_context_release(aio_context);
> >  }
> >  
> > -void qmp_block_resize(bool has_device, const char *device,
> > -                      bool has_node_name, const char *node_name,
> > -                      int64_t size, Error **errp)
> > +void coroutine_fn qmp_block_resize(bool has_device, const char *device,
> > +                                   bool has_node_name, const char *node_name,
> > +                                   int64_t size, Error **errp)
> >  {
> >      Error *local_err = NULL;
> >      BlockBackend *blk = NULL;
> 
> Pardon my ignorant question: what exactly makes a function a
> coroutine_fn?

When Stefan requested adding the coroutine_fn marker, it seemed to make
sense to me because the QMP dispatcher will always call it from
coroutine context now, and being always run in coroutine context makes a
function a coroutine_fn.

However, it's also called from hmp_block_resize(), so at least for now
coroutine_fn is actually wrong.

Kevin