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Thu, 16 Jan 2020 15:23:13 +0000 (UTC) Date: Thu, 16 Jan 2020 16:23:12 +0100 From: Kevin Wolf To: Markus Armbruster Subject: Re: [PATCH v3 4/4] block: Mark 'block_resize' as coroutine Message-ID: <20200116152312.GI9470@linux.fritz.box> References: <20200115122326.26393-1-kwolf@redhat.com> <20200115122326.26393-5-kwolf@redhat.com> <87tv4vzqd7.fsf@dusky.pond.sub.org> <20200116101333.GA9470@linux.fritz.box> <875zhbtox2.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <875zhbtox2.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: f56oqy6zOT2cAHS96bEvqw-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-block@nongnu.org, marcandre.lureau@gmail.com, qemu-devel@nongnu.org, stefanha@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 16.01.2020 um 16:13 hat Markus Armbruster geschrieben: > Kevin Wolf writes: >=20 > > Am 16.01.2020 um 10:45 hat Markus Armbruster geschrieben: > >> Kevin Wolf 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 > >> > Reviewed-by: Marc-Andr=E9 Lureau > > > >> > 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); > >> > } > >> > =20 > >> > -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 *dev= ice, > >> > + bool has_node_name, const char *= node_name, > >> > + int64_t size, Error **errp) > >> > { > >> > Error *local_err =3D NULL; > >> > BlockBackend *blk =3D NULL; > >>=20 > >> 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. >=20 > This answers the question when we mark a function a coroutine_fn. I > meant to ask what conditions the function itself must satisfy to be > eligible for this mark. The requirement is actually not about the function itself, it's about the callers, as stated above. But being a coroutine_fn allows the function to call other functions that only work in coroutine context (other coroutine_fns). In the end the reason why a function only works in coroutine context is usually that it (or any other coroutine_fns called by it) could yield, which obviously doesn't work outside of coroutine contest. Kevin