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    Subject[for-next][PATCH 12/30] tracing: Add hist trigger support for pausing and continuing a trace
    From: Tom Zanussi <tom.zanussi@linux.intel.com>

    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

    Link: http://lkml.kernel.org/r/b672a92c14702cb924cdf6fc27ea1809bed04907.1457029949.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>
    ---
    kernel/trace/trace.c | 7 ++++++-
    kernel/trace/trace_events_hist.c | 31 ++++++++++++++++++++++++++++---
    2 files changed, 34 insertions(+), 4 deletions(-)

    diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
    index d16fa8e1cdbf..7d5c63dd410a 100644
    --- a/kernel/trace/trace.c
    +++ b/kernel/trace/trace.c
    @@ -3837,6 +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 [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"
    @@ -3851,7 +3852,11 @@ 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 03ba4530c08c..e3fa9c89f125 100644
    --- a/kernel/trace/trace_events_hist.c
    +++ b/kernel/trace/trace_events_hist.c
    @@ -86,6 +86,8 @@ struct hist_trigger_attrs {
    char *keys_str;
    char *vals_str;
    char *sort_key_str;
    + bool pause;
    + bool cont;
    unsigned int map_bits;
    };

    @@ -193,6 +195,11 @@ 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=")) == 0)
    attrs->sort_key_str = kstrdup(str, GFP_KERNEL);
    + else if (strcmp(str, "pause") == 0)
    + attrs->pause = true;
    + else if ((strcmp(str, "cont") == 0) ||
    + (strcmp(str, "continue") == 0))
    + attrs->cont = true;
    else if (strncmp(str, "size=", strlen("size=")) == 0) {
    int map_bits = parse_map_size(str);

    @@ -871,7 +878,10 @@ 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');

    @@ -910,16 +920,30 @@ 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->cont) {
    + ret = -ENOENT;
    + goto out;
    + }
    +
    + if (hist_data->attrs->pause)
    + data->paused = true;
    +
    if (data->ops->init) {
    ret = data->ops->init(data->ops, data);
    if (ret < 0)
    @@ -1011,7 +1035,8 @@ 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;
    --
    2.8.0.rc3

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