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SubjectRe: [PATCH v13 06/29] tracing: Add needs_rec flag to event triggers
On Thu, 10 Dec 2015 12:50:48 -0600
Tom Zanussi <tom.zanussi@linux.intel.com> wrote:

> Add a new needs_rec flag for triggers that require unconditional
> access to trace records in order to function.
>
> Normally a trigger requires access to the contents of a trace record
> only if it has a filter associated with it (since filters need the
> contents of a record in order to make a filtering decision). Some
> types of triggers, such as 'hist' triggers, require access to trace
> record contents independent of the presence of filters, so add a new
> flag for those triggers.
>
> 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>
> ---
> kernel/trace/trace.h | 7 +++++++
> kernel/trace/trace_events_trigger.c | 3 ++-
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
> index 5e23a97..300add5 100644
> --- a/kernel/trace/trace.h
> +++ b/kernel/trace/trace.h
> @@ -1293,6 +1293,12 @@ struct event_trigger_ops {
> * itself logs to the trace buffer, this flag should be set,
> * otherwise it can be left unspecified.
> *
> + * @needs_rec: A flag that says whether or not this command needs
> + * access to the trace record in order to perform its function,
> + * regardless of whether or not it has a filter associated with
> + * it (filters make a trigger require access to the trace record
> + * but are not always present).
> + *
> * All the methods below, except for @set_filter(), must be
> * implemented.
> *
> @@ -1333,6 +1339,7 @@ struct event_command {
> char *name;
> enum event_trigger_type trigger_type;
> bool post_trigger;
> + bool needs_rec;

Note, from what I understand, gcc sucks with bool in structures. Best
thing to do here is to create a "int flags" field, and check the result
with masks.

You don't need to update this patch (I'm still working on the series),
but a patch on top of these may be necessary. I could add the patch too.

-- Steve


> int (*func)(struct event_command *cmd_ops,
> struct trace_event_file *file,
> char *glob, char *cmd, char *params);
> diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_events_trigger.c
> index 8375d29..2f881e9 100644
> --- a/kernel/trace/trace_events_trigger.c
> +++ b/kernel/trace/trace_events_trigger.c
> @@ -498,7 +498,8 @@ void update_cond_flag(struct trace_event_file *file)
> bool set_cond = false;
>
> list_for_each_entry_rcu(data, &file->triggers, list) {
> - if (data->filter || data->cmd_ops->post_trigger) {
> + if (data->filter || data->cmd_ops->post_trigger ||
> + data->cmd_ops->needs_rec) {
> set_cond = true;
> break;
> }

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