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Tue, 13 Apr 2021 08:40:59 +0200 (CEST) From: Markus Armbruster To: Li Zhang Subject: Re: [PATCH 2/2] Support monitor chardev hotswap with QMP References: <20210315170636.704201-1-zhlcindy@gmail.com> <20210315170636.704201-2-zhlcindy@gmail.com> Date: Tue, 13 Apr 2021 08:40:59 +0200 In-Reply-To: <20210315170636.704201-2-zhlcindy@gmail.com> (Li Zhang's message of "Mon, 15 Mar 2021 18:06:36 +0100") Message-ID: <8735vu1ybo.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: lukasstraub2@web.de, alexandr.iarygin@profitbricks.com, qemu-devel@nongnu.org, Li Zhang , pankaj.gupta@cloud.ionos.com, marcandre.lureau@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Li Zhang writes: > From: Li Zhang > > For some scenarios, it needs to hot-add a monitor device. > But QEMU doesn't support hotplug yet. It also works by adding > a monitor with null backend by default and then change its > backend to socket by QMP command "chardev-change". > > So this patch is to support monitor chardev hotswap with QMP. > > Signed-off-by: Li Zhang I think what what you're trying to say is that chardev-change does not work when the character device changes is used by a QMP monitor. Correct? If yes, how exactly does it misbehave? Does it work with an HMP monitor? > --- > monitor/monitor-internal.h | 3 +++ > monitor/monitor.c | 2 +- > monitor/qmp.c | 42 +++++++++++++++++++++++++++++++++++--- > 3 files changed, 43 insertions(+), 4 deletions(-) > > diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h > index 40903d6386..2df6dd21de 100644 > --- a/monitor/monitor-internal.h > +++ b/monitor/monitor-internal.h > @@ -186,4 +186,7 @@ int hmp_compare_cmd(const char *name, const char *lis= t); > void qmp_query_qmp_schema(QDict *qdict, QObject **ret_data, > Error **errp); > =20 > +gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond, > + void *opaque); > + > #endif > diff --git a/monitor/monitor.c b/monitor/monitor.c > index e94f532cf5..2d255bab18 100644 > --- a/monitor/monitor.c > +++ b/monitor/monitor.c > @@ -157,7 +157,7 @@ static inline bool monitor_is_hmp_non_interactive(con= st Monitor *mon) > =20 > static void monitor_flush_locked(Monitor *mon); > =20 > -static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond, > +gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond, > void *opaque) > { > Monitor *mon =3D opaque; > diff --git a/monitor/qmp.c b/monitor/qmp.c > index 2326bd7f9b..55cfb230d9 100644 > --- a/monitor/qmp.c > +++ b/monitor/qmp.c > @@ -44,6 +44,7 @@ struct QMPRequest { > Error *err; > }; > typedef struct QMPRequest QMPRequest; > +static void monitor_qmp_set_handlers_bh(void *opaque); > =20 > QmpCommandList qmp_commands, qmp_cap_negotiation_commands; > =20 > @@ -480,7 +481,35 @@ void monitor_data_destroy_qmp(MonitorQMP *mon) > g_queue_free(mon->qmp_requests); > } > =20 > -static void monitor_qmp_setup_handlers_bh(void *opaque) > +static int monitor_qmp_change(void *opaque) > +{ > + MonitorQMP *mon =3D opaque; > + > + mon->common.use_io_thread =3D > + qemu_chr_has_feature(mon->common.chr.chr, QEMU_CHAR_FEATURE_GCON= TEXT); > + > + if (mon->common.use_io_thread) { > + aio_bh_schedule_oneshot(iothread_get_aio_context(mon_iothread), > + monitor_qmp_set_handlers_bh, mon); > + } else { > + qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read, > + monitor_qmp_read, monitor_qmp_event, > + monitor_qmp_change, &mon->common, NULL,= true); > + } > + > + if (mon->common.out_watch) { > + g_source_remove(mon->common.out_watch); All other updates of @out_watch are under @mon_lock. Why not this one? I have no idea whether g_source_remove() is the right function to call. Its documentation says "You must use g_source_destroy() for sources added to a non-default main context." The qemu_chr_fe_set_handlers() contract is of no help. Documentation of g_source_destroy() confuses some more: "This does not unref the GSource: if you still hold a reference, use g_source_unref() to drop it. Marc-Andr=C3=A9, can you help? > + qemu_mutex_lock(&mon->common.mon_lock); > + mon->common.out_watch =3D > + qemu_chr_fe_add_watch(&mon->common.chr, G_IO_OUT | G_IO_HUP, > + monitor_unblocked, &mon->common); Bad indentation. Better: mon->common.out_watch =3D qemu_chr_fe_add_watch(&mon->common.chr, G_IO_OUT | G_IO_HUP, monitor_unblocked, &mon->common); or mon->common.out_watch =3D qemu_chr_fe_add_watch(&mon->common.chr, G_IO_OUT | G_IO_HUP, monitor_unblocked, &mon->common); or mon->common.out_watch =3D qemu_chr_fe_add_watch(&mon->common.chr, G_IO_OUT | G_IO_HUP, monitor_unblocked, &mon->common); > + qemu_mutex_unlock(&mon->common.mon_lock); > + } > + > + return 0; > +} This function copies from monitor_data_init(), monitor_init_qmp(), and monitor_flush_locked(). Feels like a refactoring would be in order. Possibly on top. > + > +static void monitor_qmp_set_handlers_bh(void *opaque) > { > MonitorQMP *mon =3D opaque; > GMainContext *context; > @@ -490,7 +519,14 @@ static void monitor_qmp_setup_handlers_bh(void *opaq= ue) > assert(context); > qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read, > monitor_qmp_read, monitor_qmp_event, > - NULL, &mon->common, context, true); > + monitor_qmp_change, &mon->common, context, = true); > + > +} > + > +static void monitor_qmp_setup_handlers_bh(void *opaque) > +{ > + MonitorQMP *mon =3D opaque; > + monitor_qmp_set_handlers_bh(mon); > monitor_list_append(&mon->common); > } > =20 > @@ -531,7 +567,7 @@ void monitor_init_qmp(Chardev *chr, bool pretty, Erro= r **errp) > } else { > qemu_chr_fe_set_handlers(&mon->common.chr, monitor_can_read, > monitor_qmp_read, monitor_qmp_event, > - NULL, &mon->common, NULL, true); > + monitor_qmp_change, &mon->common, NULL,= true); > monitor_list_append(&mon->common); > } > }