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Commit e86ae9ba authored Mar 03, 2016 by Tom Zanussi Committed by Steven Rostedt Apr 19, 2016

tracing: Add hist trigger support for clearing a trace

Allow users to append 'clear' to an existing trigger in order to have
the hash table cleared.

This expands the hist trigger syntax from this:
    # echo hist:keys=xxx:vals=yyy:sort=zzz.descending:pause/cont \
           [ if filter] >> event/trigger

to this:

    # echo hist:keys=xxx:vals=yyy:sort=zzz.descending:pause/cont/clear \
          [ if filter] >> event/trigger

Link: http://lkml.kernel.org/r/ae15dd0d9b2f7af07a37c1ff682063e2dbcdf160.1457029949.git.tom.zanussi@linux.intel.com



Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

parent 83e99914

kernel/trace/trace.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -3837,7 +3837,7 @@ static const char readme_msg[] =
		"\t [:values=<field1[,field2,...]>]\n"
		"\t [:sort=<field1[,field2,...]>]\n"
		"\t [:size=#entries]\n"
		"\t [:pause][:continue]\n"
		"\t [:pause][:continue][:clear]\n"
		"\t [if <filter>]\n\n"
		"\t When a matching event is hit, an entry is added to a hash\n"
		"\t table using the key(s) and value(s) named, and the value of a\n"
		@@ -3857,6 +3857,9 @@ static const char readme_msg[] =
		"\t trigger or to start a hist trigger but not log any events\n"
		"\t until told to do so. 'continue' can be used to start or\n"
		"\t restart a paused hist trigger.\n\n"
		"\t The 'clear' parameter will clear the contents of a running\n"
		"\t hist trigger and leave its current paused/active state\n"
		"\t unchanged.\n\n"
		#endif
		;

kernel/trace/trace_events_hist.c

+22 −2

Original line number	Diff line number	Diff line
		@@ -88,6 +88,7 @@ struct hist_trigger_attrs {
		char *sort_key_str;
		bool pause;
		bool cont;
		bool clear;
		unsigned int map_bits;
		};

		@@ -200,6 +201,8 @@ static struct hist_trigger_attrs parse_hist_trigger_attrs(char trigger_str)
		else if ((strcmp(str, "cont") == 0) \|\|
		(strcmp(str, "continue") == 0))
		attrs->cont = true;
		else if (strcmp(str, "clear") == 0)
		attrs->clear = true;
		else if (strncmp(str, "size=", strlen("size=")) == 0) {
		int map_bits = parse_map_size(str);

		@@ -916,6 +919,21 @@ static struct event_trigger_ops event_hist_get_trigger_ops(char cmd,
		return &event_hist_trigger_ops;
		}

		static void hist_clear(struct event_trigger_data *data)
		{
		struct hist_trigger_data *hist_data = data->private_data;
		bool paused;

		paused = data->paused;
		data->paused = true;

		synchronize_sched();

		tracing_map_clear(hist_data->map);

		data->paused = paused;
		}

		static int hist_register_trigger(char glob, struct event_trigger_ops ops,
		struct event_trigger_data *data,
		struct trace_event_file *file)
		@@ -930,13 +948,15 @@ static int hist_register_trigger(char glob, struct event_trigger_ops ops,
		test->paused = true;
		else if (hist_data->attrs->cont)
		test->paused = false;
		else if (hist_data->attrs->clear)
		hist_clear(test);
		else
		ret = -EEXIST;
		goto out;
		}
		}

		if (hist_data->attrs->cont) {
		if (hist_data->attrs->cont \|\| hist_data->attrs->clear) {
		ret = -ENOENT;
		goto out;
		}
		@@ -1035,7 +1055,7 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
		* triggers registered a failure too.
		*/
		if (!ret) {
		if (!(attrs->pause \|\| attrs->cont))
		if (!(attrs->pause \|\| attrs->cont \|\| attrs->clear))
		ret = -ENOENT;
		goto out_free;
		} else if (ret < 0)