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    Subject[PATCH v3 3/9] tracing: add 'traceon' and 'traceoff' event trigger commands
    Date
    Add 'traceon' and 'traceoff' ftrace_func_command commands.  traceon
    and traceoff event triggers are added by the user via these commands
    in a similar way and using practically the same syntax as the
    analagous 'traceon' and 'traceoff' ftrace function commands, but
    instead of writing to the set_ftrace_filter file, the traceon and
    traceoff triggers are written to the per-event 'trigger' files:

    echo 'traceon' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff' > .../tracing/events/somesys/someevent/trigger

    The above command will turn tracing on or off whenever someevent is
    hit.

    This also adds a 'count' version that limits the number of times the
    command will be invoked:

    echo 'traceon:N' > .../tracing/events/somesys/someevent/trigger
    echo 'traceoff:N' > .../tracing/events/somesys/someevent/trigger

    Where N is the number of times the command will be invoked.

    The above commands will will turn tracing on or off whenever someevent
    is hit, but only N times.

    The event_trigger_init() and event_trigger_free() are meant to be
    common implementations of the event_trigger_ops init() and free() ops.
    Most trigger_ops implementations will use these, but some will
    override and possibly reuse them.

    Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
    ---
    include/linux/ftrace_event.h | 1 +
    kernel/trace/trace_events_trigger.c | 313 ++++++++++++++++++++++++++++++++++++
    2 files changed, 314 insertions(+)

    diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h
    index 6cd5bbc..c794686 100644
    --- a/include/linux/ftrace_event.h
    +++ b/include/linux/ftrace_event.h
    @@ -316,6 +316,7 @@ struct ftrace_event_file {

    enum trigger_mode {
    TM_NONE = (0),
    + TM_TRACE_ONOFF = (1 << 0),
    };

    extern void destroy_preds(struct ftrace_event_call *call);
    diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
    index 1f0565c..f2b97b6 100644
    --- a/kernel/trace/trace_events_trigger.c
    +++ b/kernel/trace/trace_events_trigger.c
    @@ -355,7 +355,320 @@ static void unregister_trigger(char *glob, struct event_trigger_ops *ops,
    data->ops->free(data->ops, (void **)&data);
    }

    +int
    +event_trigger_print(const char *name, struct seq_file *m,
    + void *data, char *filter_str)
    +{
    + long count = (long)data;
    +
    + seq_printf(m, "%s", name);
    +
    + if (count == -1)
    + seq_puts(m, ":unlimited");
    + else
    + seq_printf(m, ":count=%ld", count);
    +
    + if (filter_str)
    + seq_printf(m, " if %s\n", filter_str);
    + else
    + seq_puts(m, "\n");
    +
    + return 0;
    +}
    +
    +static int
    +event_trigger_init(struct event_trigger_ops *ops, void **_data)
    +{
    + struct event_trigger_data **p = (struct event_trigger_data **)_data;
    + struct event_trigger_data *data = *p;
    +
    + data->ref++;
    + return 0;
    +}
    +
    +static void
    +event_trigger_free(struct event_trigger_ops *ops, void **_data)
    +{
    + struct event_trigger_data **p = (struct event_trigger_data **)_data;
    + struct event_trigger_data *data = *p;
    +
    + if (WARN_ON_ONCE(data->ref <= 0))
    + return;
    +
    + data->ref--;
    + if (!data->ref)
    + kfree(data);
    +}
    +
    +static int
    +event_trigger_callback(struct event_command *cmd_ops, void *cmd_data,
    + char *glob, char *cmd, char *param, int enabled)
    +{
    + struct event_trigger_ops *trigger_ops;
    + struct event_trigger_data *trigger_data;
    + char *trigger = NULL;
    + char *number;
    + int ret;
    +
    + if (!enabled)
    + return -EINVAL;
    +
    + /* separate the trigger from the filter (t:n [if filter]) */
    + if (param && isdigit(param[0]))
    + trigger = strsep(&param, " \t");
    +
    + mutex_lock(&event_mutex);
    +
    + trigger_ops = cmd_ops->get_trigger_ops(cmd, trigger);
    +
    + ret = -ENOMEM;
    + trigger_data = kzalloc(sizeof(*trigger_data), GFP_KERNEL);
    + if (!trigger_data)
    + goto out;
    +
    + trigger_data->count = -1;
    + trigger_data->ops = trigger_ops;
    + trigger_data->mode = cmd_ops->trigger_mode;
    + INIT_LIST_HEAD(&trigger_data->list);
    +
    + if (glob[0] == '!') {
    + cmd_ops->unreg(glob+1, trigger_ops, trigger_data, cmd_data);
    + kfree(trigger_data);
    + ret = 0;
    + goto out;
    + }
    +
    + if (trigger) {
    + number = strsep(&trigger, ":");
    +
    + ret = -EINVAL;
    + if (!strlen(number))
    + goto out_free;
    +
    + /*
    + * We use the callback data field (which is a pointer)
    + * as our counter.
    + */
    + ret = kstrtoul(number, 0, &trigger_data->count);
    + if (ret)
    + goto out_free;
    + }
    +
    + if (!param) /* if param is non-empty, it's supposed to be a filter */
    + goto out_reg;
    +
    + if (!cmd_ops->set_filter)
    + goto out_reg;
    +
    + ret = cmd_ops->set_filter(param, trigger_data, cmd_data);
    + if (ret < 0)
    + goto out_free;
    +
    + out_reg:
    + ret = cmd_ops->reg(glob, trigger_ops, trigger_data, cmd_data);
    + /*
    + * The above returns on success the # of functions enabled,
    + * but if it didn't find any functions it returns zero.
    + * Consider no functions a failure too.
    + */
    + if (!ret) {
    + ret = -ENOENT;
    + goto out_free;
    + } else if (ret < 0)
    + goto out_free;
    + ret = 0;
    + out:
    + mutex_unlock(&event_mutex);
    + return ret;
    +
    + out_free:
    + kfree(trigger_data);
    + goto out;
    +}
    +
    +static void
    +traceon_trigger(void **_data)
    +{
    + struct event_trigger_data **p = (struct event_trigger_data **)_data;
    + struct event_trigger_data *data = *p;
    +
    + if (!data)
    + return;
    +
    + if (tracing_is_on())
    + return;
    +
    + tracing_on();
    +}
    +
    +static void
    +traceon_count_trigger(void **_data)
    +{
    + struct event_trigger_data **p = (struct event_trigger_data **)_data;
    + struct event_trigger_data *data = *p;
    +
    + if (!data)
    + return;
    +
    + if (!data->count)
    + return;
    +
    + if (data->count != -1)
    + (data->count)--;
    +
    + traceon_trigger(_data);
    +}
    +
    +static void
    +traceoff_trigger(void **_data)
    +{
    + struct event_trigger_data **p = (struct event_trigger_data **)_data;
    + struct event_trigger_data *data = *p;
    +
    + if (!data)
    + return;
    +
    + if (!tracing_is_on())
    + return;
    +
    + tracing_off();
    +}
    +
    +static void
    +traceoff_count_trigger(void **_data)
    +{
    + struct event_trigger_data **p = (struct event_trigger_data **)_data;
    + struct event_trigger_data *data = *p;
    +
    + if (!data)
    + return;
    +
    + if (!data->count)
    + return;
    +
    + if (data->count != -1)
    + (data->count)--;
    +
    + traceoff_trigger(_data);
    +}
    +
    +static int
    +traceon_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
    + void *_data)
    +{
    + struct event_trigger_data *data = _data;
    +
    + return event_trigger_print("traceon", m, (void *)data->count,
    + data->filter_str);
    +}
    +
    +static int
    +traceoff_trigger_print(struct seq_file *m, struct event_trigger_ops *ops,
    + void *_data)
    +{
    + struct event_trigger_data *data = _data;
    +
    + return event_trigger_print("traceoff", m, (void *)data->count,
    + data->filter_str);
    +}
    +
    +static struct event_trigger_ops traceon_trigger_ops = {
    + .func = traceon_trigger,
    + .print = traceon_trigger_print,
    + .init = event_trigger_init,
    + .free = event_trigger_free,
    +};
    +
    +static struct event_trigger_ops traceon_count_trigger_ops = {
    + .func = traceon_count_trigger,
    + .print = traceon_trigger_print,
    + .init = event_trigger_init,
    + .free = event_trigger_free,
    +};
    +
    +static struct event_trigger_ops traceoff_trigger_ops = {
    + .func = traceoff_trigger,
    + .print = traceoff_trigger_print,
    + .init = event_trigger_init,
    + .free = event_trigger_free,
    +};
    +
    +static struct event_trigger_ops traceoff_count_trigger_ops = {
    + .func = traceoff_count_trigger,
    + .print = traceoff_trigger_print,
    + .init = event_trigger_init,
    + .free = event_trigger_free,
    +};
    +
    +static struct event_trigger_ops *
    +onoff_get_trigger_ops(char *cmd, char *param)
    +{
    + struct event_trigger_ops *ops;
    +
    + /* we register both traceon and traceoff to this callback */
    + if (strcmp(cmd, "traceon") == 0)
    + ops = param ? &traceon_count_trigger_ops :
    + &traceon_trigger_ops;
    + else
    + ops = param ? &traceoff_count_trigger_ops :
    + &traceoff_trigger_ops;
    +
    + return ops;
    +}
    +
    +static struct event_command trigger_traceon_cmd = {
    + .name = "traceon",
    + .trigger_mode = TM_TRACE_ONOFF,
    + .func = event_trigger_callback,
    + .reg = register_trigger,
    + .unreg = unregister_trigger,
    + .get_trigger_ops = onoff_get_trigger_ops,
    +};
    +
    +static struct event_command trigger_traceoff_cmd = {
    + .name = "traceoff",
    + .trigger_mode = TM_TRACE_ONOFF,
    + .func = event_trigger_callback,
    + .reg = register_trigger,
    + .unreg = unregister_trigger,
    + .get_trigger_ops = onoff_get_trigger_ops,
    +};
    +
    +static __init void unregister_trigger_traceon_traceoff_cmds(void)
    +{
    + unregister_event_command(&trigger_traceon_cmd,
    + &trigger_commands,
    + &trigger_cmd_mutex);
    + unregister_event_command(&trigger_traceoff_cmd,
    + &trigger_commands,
    + &trigger_cmd_mutex);
    +}
    +
    +static __init int register_trigger_traceon_traceoff_cmds(void)
    +{
    + int ret;
    +
    + ret = register_event_command(&trigger_traceon_cmd, &trigger_commands,
    + &trigger_cmd_mutex);
    + if (WARN_ON(ret < 0))
    + return ret;
    + ret = register_event_command(&trigger_traceoff_cmd, &trigger_commands,
    + &trigger_cmd_mutex);
    + if (WARN_ON(ret < 0))
    + unregister_trigger_traceon_traceoff_cmds();
    +
    + return ret;
    +}
    +
    __init int register_trigger_cmds(void)
    {
    + int ret;
    +
    + ret = register_trigger_traceon_traceoff_cmds();
    + if (ret) {
    + unregister_trigger_traceon_traceoff_cmds();
    + return ret;
    + }
    +
    return 0;
    }
    --
    1.7.11.4


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