Added trace-cmd start, stop and reset

Sometimes it is nice to just kick off the tracer without having to
record it into a trace data file. Instead of having to always
echo the commands into the tracing debugfs directory, this patch adds
the trace-cmd start, which acts like the trace-cmd record, but does
not start a command or record the trace via splice. It simply enables
the tracer.

trace-cmd stop  - will stop tracing (echo 0 > tracing_on)
trace-cmd reset - will reset the tracer (echo nop > current_tracer)

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 49 insertions, 14 deletions

diff --git a/trace-cmd.c b/trace-cmd.c
index 6719fc3..22441b8 100644
--- a/trace-cmd.c
+++ b/trace-cmd.c
@@ -1105,13 +1105,26 @@ void usage(char **argv)
 
         printf("\n"
                "%s version %s\n\n"
-               "usage: %s record [-e event][-p plugin] [-d] [-o file] [-O option ] command ...\n"
+               "usage:\n"
+               " %s record [-e event][-p plugin] [-d] [-o file] [-O option ] command ...\n"
                "          -e run command with event enabled\n"
                "          -p run command with plugin enabled\n"
                "          -d disable function tracer when running\n"
                "          -o data output file [default trace.dat]\n"
                "          -O option to enable (or disable)\n"
                "\n"
+               " %s start [-e event][-p plugin] [-d] [-O option ]\n"
+               "          Uses same options as record, but does not run a command.\n"
+               "          It only enables the tracing and exits\n"
+               "\n"
+               " %s stop\n"
+               "          Stops the tracer from recording more data.\n"
+               "          Used in conjunction with start\n"
+               "\n"
+               " %s reset\n"
+               "          Disables the tracer (may reset trace file)\n"
+               "          Used in conjunction with start\n"
+               "\n"
                " %s report [-i file] [--cpu cpu] [-e][-f][-l][-P][-E]\n"
                "          -i input file [default trace.dat]\n"
                "          -e show file endianess\n"
@@ -1124,7 +1137,7 @@ void usage(char **argv)
                "          -e list available events\n"
                "          -p list available plugins\n"
                "          -o list available options\n"
-               "\n", p, VERSION, p, p, p);
+               "\n", p, VERSION, p, p, p, p, p, p);
         exit(-1);
 }
 
@@ -1138,6 +1151,7 @@ int main (int argc, char **argv)
         int plug = 0;
         int events = 0;
         int options = 0;
+        int record = 0;
         int fset;
 
         int c;
@@ -1150,7 +1164,8 @@ int main (int argc, char **argv)
         if (strcmp(argv[1], "report") == 0) {
                 trace_report(argc, argv);
                 exit(0);
-        } else if (strcmp(argv[1], "record") == 0) {
+        } else if ((record = (strcmp(argv[1], "record") == 0)) ||
+                   (strcmp(argv[1], "start") == 0)) {
 
                 while ((c = getopt(argc-1, argv+1, "+he:p:do:O:")) >= 0) {
                         switch (c) {
@@ -1174,6 +1189,9 @@ int main (int argc, char **argv)
                                 disable = 1;
                                 break;
                         case 'o':
+                                if (!record)
+                                        die("start does not take output\n"
+                                            "Did you mean 'record'?\n");
                                 if (output)
                                         die("only one output file allowed");
                                 output = optarg;
@@ -1185,6 +1203,14 @@ int main (int argc, char **argv)
                         }
                 }
 
+        } else if (strcmp(argv[1], "stop") == 0) {
+                disable_tracing();
+                exit(0);
+
+        } else if (strcmp(argv[1], "reset") == 0) {
+                disable_all();
+                exit(0);
+
         } else if (strcmp(argv[1], "list") == 0) {
 
                 while ((c = getopt(argc-1, argv+1, "+hepo")) >= 0) {
@@ -1231,21 +1257,26 @@ int main (int argc, char **argv)
                 usage(argv);
         }
 
-        if ((argc - optind) < 2)
-                usage(argv);
+        if ((argc - optind) < 2) {
+                if (record)
+                        usage(argv);
+        } else if (!record)
+                die("Command start does not take any commands\n"
+                    "Did you mean 'record'?");
 
-        if (output)
-                output_file = output;
+        if (record) {
+                if (output)
+                        output_file = output;
 
-        read_tracing_data();
+                read_tracing_data();
 
-        fset = set_ftrace(!disable);
+                fset = set_ftrace(!disable);
 
-        disable_all();
-
-        start_threads();
+                start_threads();
+                signal(SIGINT, finish);
+        }
 
-        signal(SIGINT, finish);
+        disable_all();
 
         if (events)
                 enable_events();
@@ -1260,7 +1291,8 @@ int main (int argc, char **argv)
                     strcmp(plugin, "wakeup") == 0 ||
                     strcmp(plugin, "wakeup_rt") == 0) {
                         latency = 1;
-                        stop_threads();
+                        if (record)
+                                stop_threads();
                         reset_max_latency();
                 }
                 if (fset < 0 && (strcmp(plugin, "function") == 0 ||
@@ -1271,6 +1303,9 @@ int main (int argc, char **argv)
 
         enable_tracing();
 
+        if (!record)
+                exit(0);
+
         run_cmd((argc - optind) - 1, &argv[optind + 1]);
 
         disable_tracing();