[Qemu-devel] [Tracing][RFC] QMP interface to toggle state of a trace-event

[Prerna Saxena]

QMP command trace-event to toggle state of a trace-event.
 Illustration :
 -> { "execute": "trace-event", "arguments": { "name": "qemu_malloc", "option": 
true} }
 <- { "return": {} }

Posting this as an RFC for now. I'll post the final version as a part of
 the cumulative QMP patchset for tracing ( including patches for query-* 
commands posted earlier : 
http://lists.gnu.org/archive/html/qemu-devel/2010-10/msg01232.html )

Signed-off-by: Prerna Saxena <address@hidden>
---
 hmp-commands.hx |    2 +-
 monitor.c       |   43 +++++++++++++++++++++++++++++++++++++------
 qmp-commands.hx |   32 ++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 7 deletions(-)

diff --git a/hmp-commands.hx b/hmp-commands.hx
index 81999aa..76ec2fe 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -149,7 +149,7 @@ ETEXI
         .args_type  = "name:s,option:b",
         .params     = "name on|off",
         .help       = "changes status of a specific trace event",
-        .mhandler.cmd = do_change_trace_event_state,
+        .mhandler.cmd = do_change_trace_event_state_hmp,
     },
 
 STEXI
diff --git a/monitor.c b/monitor.c
index c7e1f53..0766ed3 100644
--- a/monitor.c
+++ b/monitor.c
@@ -545,17 +545,43 @@ static void do_help_cmd(Monitor *mon, const QDict *qdict)
 }
 
 #ifdef CONFIG_SIMPLE_TRACE
-static void do_change_trace_event_state(Monitor *mon, const QDict *qdict)
+
+/**
+ * HMP handler to change trace event state.
+ *
+ */
+void do_change_trace_event_state_hmp(Monitor *mon, const QDict *qdict)
 {
-    const char *tp_name = qdict_get_str(qdict, "name");
-    bool new_state = qdict_get_bool(qdict, "option");
-    int ret = st_change_trace_event_state(tp_name, new_state);
+    if (!do_change_trace_event_state_generic(qdict)) {
+        monitor_printf(mon, "unknown event name \"%s\"\n",
+                                      qdict_get_str(qdict, "name"));
+    }
+}
 
-    if (!ret) {
-        monitor_printf(mon, "unknown event name \"%s\"\n", tp_name);
+/**
+ * QMP handler to change trace event state.
+ *
+ */
+static int do_change_trace_event_state_qmp(Monitor *mon, const QDict *qdict,
+                                           QObject **ret_data)
+{
+    if (!do_change_trace_event_state_generic(qdict)) {
+        qerror_report(QERR_INVALID_PARAMETER, qdict_get_str(qdict, "name"));
+        return -1;
     }
+    return 0;
 }
 
+/**
+ * Generic handler to change trace event state.
+ *
+ */
+static int do_change_trace_event_state_generic(const QDict *qdict)
+{
+    const char *tp_name = qdict_get_str(qdict, "name");
+    bool new_state = qdict_get_bool(qdict, "option");
+    return st_change_trace_event_state(tp_name, new_state);
+}
 static void do_trace_file(Monitor *mon, const QDict *qdict)
 {
     const char *op = qdict_get_try_str(qdict, "op");
@@ -583,6 +609,11 @@ static void do_info_trace_file_to_qmp(Monitor *mon, 
QObject **ret_data)
 {
     *ret_data = st_print_file_to_qobject();
 }
+
+#else
+static int do_change_trace_event_state_qmp(Monitor *mon, const QDict *qdict,
+QObject **ret_data) {}
+
 #endif
 
 static void user_monitor_complete(void *opaque, QObject *ret_data)
diff --git a/qmp-commands.hx b/qmp-commands.hx
index bc79b55..7613d73 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -761,6 +761,38 @@ Example:
 
 Note: This command must be issued before issuing any other command.
 
+EQMP
+
+    {
+        .name       = "trace-event",
+        .args_type  = "name:s,option:b",
+        .params     = "name on|off",
+        .help       = "changes state of a specific trace event",
+        .user_print = monitor_user_noop,
+        .mhandler.cmd_new = do_change_trace_event_state_qmp,
+    },
+
+SQMP
+trace-event
+-----------
+
+Change state of a trace-event.
+
+Arguments:
+
+- "name": name of trace-event (json-string)
+- "option": new state for the trace-event (json-bool)
+
+Example:
+
+-> { "execute": "trace-event", "arguments": { "name": "ABC", "option":false } }
+<- { "return": {} }
+
+Notes:
+
+(1) The 'query-trace-events' command should be used to check the new state 
+    of the trace-event.
+
 3. Query Commands
 =================
 
-- 
1.7.2.3



-- 
Prerna Saxena

Linux Technology Centre,
IBM Systems and Technology Lab,
Bangalore, India