ftrace: tracing header should put '#' at the beginning of a line

In a recent discussion, Andrew Morton pointed out that tracing header
should put '#' at the beginning of a line.

Then, we can easily filtered the header by following grep usage:

  cat trace | grep -v '^#'

Wakeup trace also has the same header problem.

Comparison of headers displayed:

before this patch:

 # tracer: wakeup
 #
 wakeup latency trace v1.1.5 on 2.6.29-rc7-tip-tip
 --------------------------------------------------------------------
  latency: 19059 us, #21277/21277, CPU#1 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4)
     -----------------
     | task: kondemand/1-1644 (uid:0 nice:-5 policy:0 rt_prio:0)
     -----------------

 #                  _------=> CPU#
 #                 / _-----=> irqs-off
 #                | / _----=> need-resched
 #                || / _---=> hardirq/softirq
 #                ||| / _--=> preempt-depth
 #                |||| /
 #                |||||     delay
 #  cmd     pid   ||||| time  |   caller
 #     \   /      |||||   \   |   /
 irqbalan-1887    1d.s.    0us :   1887:120:R   + [001]  1644:115:S kondemand/1
 irqbalan-1887    1d.s.    1us : default_wake_function <-autoremove_wake_function
 irqbalan-1887    1d.s.    2us : check_preempt_wakeup <-try_to_wake_up

after this patch:

 # tracer: wakeup
 #
 # wakeup latency trace v1.1.5 on 2.6.29-rc7-tip-tip
 # --------------------------------------------------------------------
 # latency: 529 us, #530/530, CPU#0 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:4)
 #    -----------------
 #    | task: kondemand/0-1641 (uid:0 nice:-5 policy:0 rt_prio:0)
 #    -----------------
 #
 #                  _------=> CPU#
 #                 / _-----=> irqs-off
 #                | / _----=> need-resched
 #                || / _---=> hardirq/softirq
 #                ||| / _--=> preempt-depth
 #                |||| /
 #                |||||     delay
 #  cmd     pid   ||||| time  |   caller
 #     \   /      |||||   \   |   /
     sshd-2496    0d.s.    0us :   2496:120:R   + [000]  1641:115:S kondemand/0
     sshd-2496    0d.s.    1us : default_wake_function <-autoremove_wake_function
     sshd-2496    0d.s.    1us : check_preempt_wakeup <-try_to_wake_up
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
LKML-Reference: <20090308124421.23C3.A69D9226@jp.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/trace/trace.c

@@ -1466,11 +1466,11 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 	total = entries +
 		ring_buffer_overruns(iter->tr->buffer);
 
-	seq_printf(m, "%s latency trace v1.1.5 on %s\n",
+	seq_printf(m, "# %s latency trace v1.1.5 on %s\n",
 		   name, UTS_RELEASE);
-	seq_puts(m, "-----------------------------------"
+	seq_puts(m, "# -----------------------------------"
 		 "---------------------------------\n");
-	seq_printf(m, " latency: %lu us, #%lu/%lu, CPU#%d |"
+	seq_printf(m, "# latency: %lu us, #%lu/%lu, CPU#%d |"
 		   " (M:%s VP:%d, KP:%d, SP:%d HP:%d",
 		   nsecs_to_usecs(data->saved_latency),
 		   entries,
@@ -1492,24 +1492,24 @@ print_trace_header(struct seq_file *m, struct trace_iterator *iter)
 #else
 	seq_puts(m, ")\n");
 #endif
-	seq_puts(m, "    -----------------\n");
-	seq_printf(m, "    | task: %.16s-%d "
+	seq_puts(m, "#    -----------------\n");
+	seq_printf(m, "#    | task: %.16s-%d "
 		   "(uid:%d nice:%ld policy:%ld rt_prio:%ld)\n",
 		   data->comm, data->pid, data->uid, data->nice,
 		   data->policy, data->rt_priority);
-	seq_puts(m, "    -----------------\n");
+	seq_puts(m, "#    -----------------\n");
 
 	if (data->critical_start) {
-		seq_puts(m, " => started at: ");
+		seq_puts(m, "#  => started at: ");
 		seq_print_ip_sym(&iter->seq, data->critical_start, sym_flags);
 		trace_print_seq(m, &iter->seq);
-		seq_puts(m, "\n => ended at:   ");
+		seq_puts(m, "\n#  => ended at:   ");
 		seq_print_ip_sym(&iter->seq, data->critical_end, sym_flags);
 		trace_print_seq(m, &iter->seq);
-		seq_puts(m, "\n");
+		seq_puts(m, "#\n");
 	}
 
-	seq_puts(m, "\n");
+	seq_puts(m, "#\n");
 }
 
 static void test_cpu_buff_start(struct trace_iterator *iter)