Re: [Qemu-devel] [PULL v2 13/32] qmp: Revert change to handle_qmp_command tracepoint

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> On 3 July 2018 at 22:35, Markus Armbruster <address@hidden> wrote:
>> Commit 71da4667db6 "monitor: separate QMP parser and dispatcher" moved
>> the handle_qmp_command tracepoint from handle_qmp_command() to
>> monitor_qmp_dispatch_one().  This delays tracing from enqueue time to
>> dequeue time.  Revert that.  Dequeue remains adequately visible via
>> tracepoint monitor_qmp_cmd_in_band.
>>
>> Signed-off-by: Markus Armbruster <address@hidden>
>> Reviewed-by: Eric Blake <address@hidden>
>> Message-Id: <address@hidden>
>
> Hi; it looks like this revert has reintroduced(?) a coverity
> warning:
>
>> ---
>>  monitor.c | 12 ++++++------
>>  1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/monitor.c b/monitor.c
>> index 3bf3e68bdc..3cc4b07788 100644
>> --- a/monitor.c
>> +++ b/monitor.c
>> @@ -4184,12 +4184,6 @@ static void monitor_qmp_dispatch_one(QMPRequest 
>> *req_obj)
>>
>>      g_free(req_obj);
>>
>> -    if (trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
>> -        QString *req_json = qobject_to_json(req);
>> -        trace_handle_qmp_command(mon, qstring_get_str(req_json));
>> -        qobject_unref(req_json);
>> -    }
>> -
>>      old_mon = cur_mon;
>>      cur_mon = mon;
>>
>> @@ -4283,6 +4277,12 @@ static void handle_qmp_command(JSONMessageParser 
>> *parser, GQueue *tokens)
>>          qdict_del(qdict, "id");
>>      } /* else will fail qmp_dispatch() */
>>
>> +    if (trace_event_get_state_backends(TRACE_HANDLE_QMP_COMMAND)) {
>> +        QString *req_json = qobject_to_json(req);
>> +        trace_handle_qmp_command(mon, qstring_get_str(req_json));
>> +        qobject_unref(req_json);
>> +    }
>
> Coverity CID 1394216 points out that in this function a
> little earlier we did a check on "if (!req && !err)", which
> implies that we can get here with a NULL req pointer,
> which will crash in qobject_to_json().

Since fixed in
commit 8720e63e monitor: Fix tracepoint crash on JSON syntax error

>> +
>>      /* Check against the request in general layout */
>>      qdict = qmp_dispatch_check_obj(req, qmp_oob_enabled(mon), &err);
>>      if (!qdict) {
>> --

Thanks anyway!