[PATCH v11 13/28] tracing: Add hist trigger support for pausing and continuing a trace

From: Tom Zanussi
Date: Thu Oct 22 2015 - 14:19:39 EST


Allow users to append 'pause' or 'continue' to an existing trigger in
order to have it paused or to have a paused trace continue.

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

to this:

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

Signed-off-by: Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
---
kernel/trace/trace.c | 7 ++++++-
kernel/trace/trace_events_hist.c | 26 +++++++++++++++++++++++---
2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index efa8d05..a223959 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3802,6 +3802,7 @@ static const char readme_msg[] =
"\t [:values=<field1[,field2,...]]\n"
"\t [:sort=field1,field2,...]\n"
"\t [:size=#entries]\n"
+ "\t [:pause][:continue]\n"
"\t [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"
@@ -3816,7 +3817,11 @@ static const char readme_msg[] =
"\t used to specify more or fewer than the default 2048 entries\n"
"\t for the hashtable size.\n\n"
"\t Reading the 'hist' file for the event will dump the hash\n"
- "\t table in its entirety to stdout."
+ "\t table in its entirety to stdout.\n\n"
+ "\t The 'pause' parameter can be used to pause an existing hist\n"
+ "\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"
#endif
;

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 4fc3136..8753c3b 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -78,6 +78,8 @@ struct hist_trigger_attrs {
char *keys_str;
char *vals_str;
char *sort_key_str;
+ bool pause;
+ bool cont;
unsigned int map_bits;
};

@@ -184,6 +186,11 @@ static struct hist_trigger_attrs *parse_hist_trigger_attrs(char *trigger_str)
attrs->vals_str = kstrdup(str, GFP_KERNEL);
else if (!strncmp(str, "sort", strlen("sort")))
attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
+ else if (!strncmp(str, "pause", strlen("pause")))
+ attrs->pause = true;
+ else if (!strncmp(str, "continue", strlen("continue")) ||
+ !strncmp(str, "cont", strlen("cont")))
+ attrs->cont = true;
else if (!strncmp(str, "size", strlen("size"))) {
int map_bits = parse_map_size(str);

@@ -843,7 +850,10 @@ static int event_hist_trigger_print(struct seq_file *m,
if (data->filter_str)
seq_printf(m, " if %s", data->filter_str);

- seq_puts(m, " [active]");
+ if (data->paused)
+ seq_puts(m, " [paused]");
+ else
+ seq_puts(m, " [active]");

seq_putc(m, '\n');

@@ -882,16 +892,25 @@ static int hist_register_trigger(char *glob, struct event_trigger_ops *ops,
struct event_trigger_data *data,
struct trace_event_file *file)
{
+ struct hist_trigger_data *hist_data = data->private_data;
struct event_trigger_data *test;
int ret = 0;

list_for_each_entry_rcu(test, &file->triggers, list) {
if (test->cmd_ops->trigger_type == ETT_EVENT_HIST) {
- ret = -EEXIST;
+ if (hist_data->attrs->pause)
+ test->paused = true;
+ else if (hist_data->attrs->cont)
+ test->paused = false;
+ else
+ ret = -EEXIST;
goto out;
}
}

+ if (hist_data->attrs->pause)
+ data->paused = true;
+
if (data->ops->init) {
ret = data->ops->init(data->ops, data);
if (ret < 0)
@@ -984,7 +1003,8 @@ static int event_hist_trigger_func(struct event_command *cmd_ops,
* triggers registered a failure too.
*/
if (!ret) {
- ret = -ENOENT;
+ if (!(attrs->pause || attrs->cont))
+ ret = -ENOENT;
goto out_free;
} else if (ret < 0)
goto out_free;
--
1.9.3

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