trace: improve runstate tracing

Trace previous state, move tracepoint to runstate_set start (to cover
all cases for debugging), add string representations of traced states.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-id: 20190124125154.474650-1-vsementsov@virtuozzo.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

trace-events

@@ -34,9 +34,9 @@ cpu_out(unsigned int addr, char size, unsigned int val) "addr 0x%x(%c) value %u"
 balloon_event(void *opaque, unsigned long addr) "opaque %p addr %lu"
 
 # vl.c
-vm_state_notify(int running, int reason) "running %d reason %d"
+vm_state_notify(int running, int reason, const char *reason_str) "running %d reason %d (%s)"
 load_file(const char *name, const char *path) "name %s location %s"
-runstate_set(int new_state) "new state %d"
+runstate_set(int current_state, const char *current_state_str, int new_state, const char *new_state_str) "current_run_state %d (%s) new_state %d (%s)"
 system_wakeup_request(int reason) "reason=%d"
 qemu_system_shutdown_request(int reason) "reason=%d"
 qemu_system_powerdown_request(void) ""

vl.c

@@ -731,6 +731,9 @@ void runstate_set(RunState new_state)
 {
     assert(new_state < RUN_STATE__MAX);
 
+    trace_runstate_set(current_run_state, RunState_str(current_run_state),
+                       new_state, RunState_str(current_run_state));
+
     if (current_run_state == new_state) {
         return;
     }
@@ -741,7 +744,7 @@ void runstate_set(RunState new_state)
                      RunState_str(new_state));
         abort();
     }
-    trace_runstate_set(new_state);
+
     current_run_state = new_state;
 }
 
@@ -1554,7 +1557,7 @@ void vm_state_notify(int running, RunState state)
 {
     VMChangeStateEntry *e, *next;
 
-    trace_vm_state_notify(running, state);
+    trace_vm_state_notify(running, state, RunState_str(state));
 
     QLIST_FOREACH_SAFE(e, &vm_change_state_head, entries, next) {
         e->cb(e->opaque, running, state);