tracing: Revert "tracing: Remove pid in task_rename tracing output"

This reverts commit e3f6a42.

The commit says that the tracepoint only deals with the current task,
however the following case is not current task:

comm_write() {
    p = get_proc_task(inode);
    if (!p)
        return -ESRCH;

    if (same_thread_group(current, p))
        set_task_comm(p, buffer);
}
where set_task_comm() calls __set_task_comm() which records
the update of p and not current.

So revert the patch to show pid.

Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Cc: <[email protected]>
Link: https://patch.msgid.link/[email protected]
Fixes: e3f6a42 ("tracing: Remove pid in task_rename tracing output")
Reported-by: Guohua Yan <[email protected]>
Signed-off-by: Xuewen Yan <[email protected]>
Reviewed-by: Steven Rostedt (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

Author: Xuewen Yan

include/trace/events/task.h

@@ -38,19 +38,22 @@ TRACE_EVENT(task_rename,
 	TP_ARGS(task, comm),
 
 	TP_STRUCT__entry(
+		__field(	pid_t,	pid)
 		__array(	char, oldcomm,  TASK_COMM_LEN)
 		__array(	char, newcomm,  TASK_COMM_LEN)
 		__field(	short,	oom_score_adj)
 	),
 
 	TP_fast_assign(
+		__entry->pid = task->pid;
 		memcpy(entry->oldcomm, task->comm, TASK_COMM_LEN);
 		strscpy(entry->newcomm, comm, TASK_COMM_LEN);
 		__entry->oom_score_adj = task->signal->oom_score_adj;
 	),
 
-	TP_printk("oldcomm=%s newcomm=%s oom_score_adj=%hd",
-		  __entry->oldcomm, __entry->newcomm, __entry->oom_score_adj)
+	TP_printk("pid=%d oldcomm=%s newcomm=%s oom_score_adj=%hd",
+		__entry->pid, __entry->oldcomm,
+		__entry->newcomm, __entry->oom_score_adj)
 );
 
 /**