Hi On Fri, Apr 16, 2021 at 6:51 PM Markus Armbruster wrote: > Marc-André, I'd like your opinion for this one, in particular the use of > g_source_remove(). > My opinion isn't really worth much, my review would have a bit more value. GSource has indeed some peculiar lifetime management, that I got wrong in the past. So I would be extra careful. But before spending time on review, I would also clarify the motivation and ask for testing. Markus, hot-adding/removing monitors isn't supported? > Li Zhang writes: > > > 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 > > Reviewed-by: Pankaj Gupta > > Your commit message starts with a brief description of the problem. > Appreciated! But I think it could be a bit clearer. What about this: > > qmp: Support chardev-change > > For some scenarios, we'd like to hot-add a monitor device. But QEMU > doesn't support that, yet. It does support hot-swapping character > backends with QMP command chardev-change. This lets us pre-add a > monitor with a null character backend, then chardev-change to a > socket backend. Except the chardev-change fails with "Chardev user > does not support chardev hotswap" because monitors don't provide the > required callback. Implement it for QMP monitors. > > > --- > > v1 -> v2: > > - Change mutex lock mon_lock section > > - Fix indentation problems > > > > monitor/monitor-internal.h | 3 +++ > > monitor/monitor.c | 2 +- > > monitor/qmp.c | 43 +++++++++++++++++++++++++++++++++++--- > > 3 files changed, 44 insertions(+), 4 deletions(-) > > > > diff --git a/monitor/monitor-internal.h b/monitor/monitor-internal.h > > index 9c3a09cb01..1b80c74883 100644 > > --- a/monitor/monitor-internal.h > > +++ b/monitor/monitor-internal.h > > @@ -183,4 +183,7 @@ void help_cmd(Monitor *mon, const char *name); > > void handle_hmp_command(MonitorHMP *mon, const char *cmdline); > > int hmp_compare_cmd(const char *name, const char *list); > > > > +gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond, > > + void *opaque); > > + > > #endif > > diff --git a/monitor/monitor.c b/monitor/monitor.c > > index 636bcc81c5..16a3620d02 100644 > > --- a/monitor/monitor.c > > +++ b/monitor/monitor.c > > @@ -157,7 +157,7 @@ static inline bool > monitor_is_hmp_non_interactive(const Monitor *mon) > > > > static void monitor_flush_locked(Monitor *mon); > > > > -static gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond, > > +gboolean monitor_unblocked(GIOChannel *chan, GIOCondition cond, > > void *opaque) > > { > > Monitor *mon = opaque; > > diff --git a/monitor/qmp.c b/monitor/qmp.c > > index 2b0308f933..5fa65401ae 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); > > > > QmpCommandList qmp_commands, qmp_cap_negotiation_commands; > > > > @@ -477,7 +478,36 @@ void monitor_data_destroy_qmp(MonitorQMP *mon) > > g_queue_free(mon->qmp_requests); > > } > > > > -static void monitor_qmp_setup_handlers_bh(void *opaque) > > +static int monitor_qmp_change (void *opaque) > > +{ > > + MonitorQMP *mon = opaque; > > + > > + mon->common.use_io_thread = > qemu_chr_has_feature(mon->common.chr.chr, > > + QEMU_CHAR_FEATURE_GCONTEXT); > > + > > + 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); > > + } > > + > > + qemu_mutex_lock(&mon->common.mon_lock); > > + if (mon->common.out_watch) { > > + g_source_remove(mon->common.out_watch); > > + mon->common.out_watch = qemu_chr_fe_add_watch(&mon->common.chr, > > + G_IO_OUT | G_IO_HUP, > > + monitor_unblocked, > > + &mon->common); > > Visually align the arguments: > > mon->common.out_watch = qemu_chr_fe_add_watch(&mon->common.chr, > G_IO_OUT | G_IO_HUP, > monitor_unblocked, > &mon->common); > > You may reduce argument indentation some to gain extra space, but keep > the arguments more indented than the function: > > mon->common.out_watch = qemu_chr_fe_add_watch(&mon->common.chr, > G_IO_OUT | G_IO_HUP, > monitor_unblocked, &mon->common); > > Do this only when you actually use the extra space for readability. > > > + } > > + qemu_mutex_unlock(&mon->common.mon_lock); > > + > > + return 0; > > +} > > As I wrote in my review of v1, this function copies from > monitor_data_init(), monitor_init_qmp(), and monitor_flush_locked(). > Feels like a refactoring would be in order. Doing it on top might be > easier. > > > + > > +static void monitor_qmp_set_handlers_bh(void *opaque) > > { > > MonitorQMP *mon = opaque; > > GMainContext *context; > > @@ -487,7 +517,14 @@ static void monitor_qmp_setup_handlers_bh(void > *opaque) > > 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 = opaque; > > + monitor_qmp_set_handlers_bh(mon); > > monitor_list_append(&mon->common); > > } > > > > @@ -528,7 +565,7 @@ void monitor_init_qmp(Chardev *chr, bool pretty, > Error **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); > > } > > } > > > -- Marc-André Lureau