qmp: Fail gracefully if chardev is already in use

Trying to attach a QMP monitor to a chardev that is already in use
results in a crash because monitor_init_qmp() passes &error_abort to
qemu_chr_fe_init():

$ ./x86_64-softmmu/qemu-system-x86_64 --chardev stdio,id=foo --mon foo,mode=control --mon foo,mode=control
Unexpected error in qemu_chr_fe_init() at chardev/char-fe.c:220:
qemu-system-x86_64: --mon foo,mode=control: Device 'foo' is in use
Abgebrochen (Speicherabzug geschrieben)

Fix this by allowing monitor_init_qmp() to return an error and passing
any error in qemu_chr_fe_init() to its caller instead of aborting.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20200224143008.13362-18-kwolf@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/stubs/monitor-core.c b/stubs/monitor-core.c
index 403c00a6d0..6cff1c4e1d 100644
--- a/stubs/monitor-core.c
+++ b/stubs/monitor-core.c
@@ -5,7 +5,7 @@
 
 __thread Monitor *cur_mon;
 
-void monitor_init_qmp(Chardev *chr, bool pretty)
+void monitor_init_qmp(Chardev *chr, bool pretty, Error **errp)
 {
 }