From: Christian Brauner <brauner@kernel.org>

The monitor_accept_input API is called from a bottom half, and will
invoke qemu_chr_fe_accept_input().

When a following patch introduces the ability to delete monitors, it
will be neccesary to delete the bottom half. Protecting the call to
qemu_chr_fe_accept_input with the monitor lock will allow for
synchronization with the deletion process.

Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
[DB: extracted from a larger commit and refactored to apply
     to the new monitor class structure]
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 monitor/hmp.c     | 2 ++
 monitor/monitor.c | 6 +-----
 monitor/qmp.c     | 9 +++++++++
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/monitor/hmp.c b/monitor/hmp.c
index 75b93f29a3..71a1888249 100644
--- a/monitor/hmp.c
+++ b/monitor/hmp.c
@@ -116,9 +116,11 @@ static void monitor_hmp_accept_input(Monitor *mon)
         MonitorHMP *hmp = MONITOR_HMP(mon);
         assert(hmp->rs);
         readline_restart(hmp->rs);
+        qemu_chr_fe_accept_input(&mon->chr);
         qemu_mutex_unlock(&mon->mon_lock);
         readline_show_prompt(hmp->rs);
     } else {
+        qemu_chr_fe_accept_input(&mon->chr);
         qemu_mutex_unlock(&mon->mon_lock);
     }
 }
diff --git a/monitor/monitor.c b/monitor/monitor.c
index de1f761041..4a45c15a36 100644
--- a/monitor/monitor.c
+++ b/monitor/monitor.c
@@ -562,11 +562,7 @@ static void monitor_accept_input(void *opaque)
     Monitor *mon = opaque;
     MonitorClass *cls = MONITOR_GET_CLASS(mon);
 
-    if (cls->accept_input) {
-        cls->accept_input(mon);
-    }
-
-    qemu_chr_fe_accept_input(&mon->chr);
+    cls->accept_input(mon);
 }
 
 void monitor_resume(Monitor *mon)
diff --git a/monitor/qmp.c b/monitor/qmp.c
index 1c67f40e4a..dc15809145 100644
--- a/monitor/qmp.c
+++ b/monitor/qmp.c
@@ -107,6 +107,7 @@ static void monitor_qmp_emit_event(Monitor *mon, QAPIEvent event, QDict *qdict);
 static bool monitor_qmp_requires_iothread(const Monitor *mon);
 static void monitor_qmp_complete(UserCreatable *uc, Error **errp);
 static bool monitor_qmp_prepare_delete(UserCreatable *uc, Error **errp);
+static void monitor_qmp_accept_input(Monitor *mon);
 
 static void monitor_qmp_class_init(ObjectClass *cls, const void *data)
 {
@@ -119,6 +120,7 @@ static void monitor_qmp_class_init(ObjectClass *cls, const void *data)
 
     moncls->emit_event = monitor_qmp_emit_event;
     moncls->requires_iothread = monitor_qmp_requires_iothread;
+    moncls->accept_input = monitor_qmp_accept_input;
 
     ucc->complete = monitor_qmp_complete;
     ucc->prepare_delete = monitor_qmp_prepare_delete;
@@ -665,3 +667,10 @@ static bool monitor_qmp_prepare_delete(UserCreatable *uc, Error **errp)
     error_setg(errp, "Deleting QMP monitors is not supported");
     return false;
 }
+
+static void monitor_qmp_accept_input(Monitor *mon)
+{
+    WITH_QEMU_LOCK_GUARD(&mon->mon_lock) {
+        qemu_chr_fe_accept_input(&mon->chr);
+    }
+}
-- 
2.55.0