trace: add "-trace enable=..."

Allow enabling events without going through a file, for example:

   qemu-system-x86_64 -trace bdrv_aio_writev -trace bdrv_aio_readv

or with globbing too:

   qemu-system-x86_64 -trace 'bdrv_aio_*'

if an appropriate backend is enabled (simple, stderr, ftrace).

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-id: 1452174932-28657-6-git-send-email-den@openvz.org
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

2 files changed, 36 insertions, 21 deletions

diff --git a/trace/control.c b/trace/control.c
index f5a497a391..af92705bb4 100644
--- a/trace/control.c
+++ b/trace/control.c
@@ -88,6 +88,32 @@ TraceEvent *trace_event_pattern(const char *pat, TraceEvent *ev)
     return NULL;
 }
 
+void trace_enable_events(const char *line_buf)
+{
+    const bool enable = ('-' != line_buf[0]);
+    const char *line_ptr = enable ? line_buf : line_buf + 1;
+
+    if (trace_event_is_pattern(line_ptr)) {
+        TraceEvent *ev = NULL;
+        while ((ev = trace_event_pattern(line_ptr, ev)) != NULL) {
+            if (trace_event_get_state_static(ev)) {
+                trace_event_set_state_dynamic(ev, enable);
+            }
+        }
+    } else {
+        TraceEvent *ev = trace_event_name(line_ptr);
+        if (ev == NULL) {
+            error_report("WARNING: trace event '%s' does not exist",
+                         line_ptr);
+        } else if (!trace_event_get_state_static(ev)) {
+            error_report("WARNING: trace event '%s' is not traceable",
+                         line_ptr);
+        } else {
+            trace_event_set_state_dynamic(ev, enable);
+        }
+    }
+}
+
 void trace_init_events(const char *fname)
 {
     Location loc;
@@ -114,27 +140,7 @@ void trace_init_events(const char *fname)
             if ('#' == line_buf[0]) { /* skip commented lines */
                 continue;
             }
-            const bool enable = ('-' != line_buf[0]);
-            char *line_ptr = enable ? line_buf : line_buf + 1;
-            if (trace_event_is_pattern(line_ptr)) {
-                TraceEvent *ev = NULL;
-                while ((ev = trace_event_pattern(line_ptr, ev)) != NULL) {
-                    if (trace_event_get_state_static(ev)) {
-                        trace_event_set_state_dynamic(ev, enable);
-                    }
-                }
-            } else {
-                TraceEvent *ev = trace_event_name(line_ptr);
-                if (ev == NULL) {
-                    error_report("WARNING: trace event '%s' does not exist",
-                                 line_ptr);
-                } else if (!trace_event_get_state_static(ev)) {
-                    error_report("WARNING: trace event '%s' is not traceable",
-                                 line_ptr);
-                } else {
-                    trace_event_set_state_dynamic(ev, enable);
-                }
-            }
+            trace_enable_events(line_buf);
         }
     }
     if (fclose(fp) != 0) {
diff --git a/trace/control.h b/trace/control.h
index d50f3996c7..d5081ce169 100644
--- a/trace/control.h
+++ b/trace/control.h
@@ -181,6 +181,15 @@ void trace_init_events(const char *file);
  */
 void trace_init_file(const char *file);
 
+/**
+ * trace_enable_events:
+ * @line_buf: A string with a glob pattern of events to be enabled or,
+ *            if the string starts with '-', disabled.
+ *
+ * Enable or disable matching events.
+ */
+void trace_enable_events(const char *line_buf);
+
 
 #include "trace/control-internal.h"