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>

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7d5c63dd410a97bd36eaf6a98cab9ec57c4ea015..4097cd3763f7fed5af981b4e135dd9a99140440f 100644 (file)
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -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
 ;
 

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index e3fa9c89f12521d981fcd1af7a51bd1ceec996b8..83cb25e067ad21b9c4f379a9908bcbb6c5fe7ada 100644 (file)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -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)