Merge remote-tracking branch 'stefanha/tracing' into staging

* stefanha/tracing:
  trace: Remove "info trace" from documents
  trace: document '-' syntax for disabling events
  trace: allow disabling events in events file
  Avoid all systemtap reserved words

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

docs/tracing.txt

@@ -139,6 +139,10 @@ having a common prefix in a batch. For example, virtio-blk trace events could
 be enabled using:
   trace-event virtio_blk_* on
 
+If a line in the "-trace events=<file>" file begins with a '-', the trace event
+will be disabled instead of enabled.  This is useful when a wildcard was used
+to enable an entire family of events but one noisy event needs to be disabled.
+
 == Trace backends ==
 
 The "tracetool" script automates tedious trace event code generation and also
@@ -185,15 +189,6 @@ records the char* pointer value instead of the string that is pointed to.
 
 ==== Monitor commands ====
 
-* info trace
-  Display the contents of trace buffer.  This command dumps the trace buffer
-  with simple formatting.  For full pretty-printing, use the simpletrace.py
-  script on a binary trace file.
-
-  The trace buffer is written into until full.  The full trace buffer is
-  flushed and emptied.  This means the 'info trace' will display few or no
-  entries if the buffer has just been flushed.
-
 * trace-file on|off|flush|set <path>
   Enable/disable/flush the trace file or set the trace file name.
 

hmp-commands.hx

@@ -1573,13 +1573,6 @@ show roms
 @end table
 ETEXI
 
-#ifdef CONFIG_TRACE_SIMPLE
-STEXI
-@item info trace
-show contents of trace buffer
-ETEXI
-#endif
-
 STEXI
 @item info trace-events
 show available trace events and their state

scripts/tracetool/backend/dtrace.py

@@ -73,6 +73,15 @@ def d(events):
         '};')
 
 
+# Technically 'self' is not used by systemtap yet, but
+# they recommended we keep it in the reserved list anyway
+RESERVED_WORDS = (
+    'break', 'catch', 'continue', 'delete', 'else', 'for',
+    'foreach', 'function', 'global', 'if', 'in', 'limit',
+    'long', 'next', 'probe', 'return', 'self', 'string',
+    'try', 'while'
+    )
+
 def stap(events):
     for e in events:
         # Define prototype for probe arguments
@@ -87,7 +96,7 @@ def stap(events):
         if len(e.args) > 0:
             for name in e.args.names():
                 # Append underscore to reserved keywords
-                if name in ('limit', 'in', 'next', 'self', 'function'):
+                if name in RESERVED_WORDS:
                     name += '_'
                 out('  %s = $arg%d;' % (name, i))
                 i += 1

trace/control.c

@@ -12,6 +12,8 @@
 
 void trace_backend_init_events(const char *fname)
 {
+    int ret;
+
     if (fname == NULL) {
         return;
     }
@@ -30,7 +32,12 @@ void trace_backend_init_events(const char *fname)
             if ('#' == line_buf[0]) { /* skip commented lines */
                 continue;
             }
-            if (!trace_event_set_state(line_buf, true)) {
+            if ('-' == line_buf[0]) {
+                ret = trace_event_set_state(line_buf+1, false);
+            } else {
+                ret = trace_event_set_state(line_buf, true);
+            }
+            if (!ret) {
                 fprintf(stderr,
                         "error: trace event '%s' does not exist\n", line_buf);
                 exit(1);