Re: [PATCH 4/7] tracing: new format for specialized trace points

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

Hi Steven,

>  TRACE_EVENT(sched_switch,
> 
> 	TP_PROTO(struct rq *rq, struct task_struct *prev,
> 		 struct task_struct *next),
> 
> 	TP_ARGS(rq, prev, next),
> 
> 	TP_STRUCT__entry(
> 		__array(	char,	prev_comm,	TASK_COMM_LEN	)
> 		__field(	pid_t,	prev_pid			)
> 		__field(	int,	prev_prio			)
> 		__array(	char,	next_comm,	TASK_COMM_LEN	)
> 		__field(	pid_t,	next_pid			)
> 		__field(	int,	next_prio			)
> 	),
> 
> 	TP_printk("task %s:%d [%d] ==> %s:%d [%d]",
> 		__entry->prev_comm, __entry->prev_pid, __entry->prev_prio,
> 		__entry->next_comm, __entry->next_pid, __entry->next_prio),
> 
> 	TP_fast_assign(
> 		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);
> 		__entry->prev_pid	= prev->pid;
> 		__entry->prev_prio	= prev->prio;
> 		memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);
> 		__entry->next_pid	= next->pid;
> 		__entry->next_prio	= next->prio;
> 	)
>  );

Could you please write the documentation how to make new tracepont and 
use various TP_ macro?
Some developer (include me) plan to add new tracepoint. but these macro
usage is a bit difficult.