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Commit 7ee1768d authored by Pekka Paalanen's avatar Pekka Paalanen Committed by Ingo Molnar
Browse files

x86, mmiotrace: fix buffer overrun detection 



Impact: fix mmiotrace overrun tracing

When ftrace framework moved to use the ring buffer facility, the buffer
overrun detection was broken after 2.6.27 by commit

| commit 3928a8a2
| Author: Steven Rostedt <rostedt@goodmis.org>
| Date:   Mon Sep 29 23:02:41 2008 -0400
|
|     ftrace: make work with new ring buffer
|
|     This patch ports ftrace over to the new ring buffer.

The detection is now fixed by using the ring buffer API.

When mmiotrace detects a buffer overrun, it will report the number of
lost events. People reading an mmiotrace log must know if something was
missed, otherwise the data may not make sense.

Signed-off-by: default avatarPekka Paalanen <pq@iki.fi>
Acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 522a110b

kernel/trace/trace_mmiotrace.c

+7 −9
Original line number Diff line number Diff line
@@ -18,12 +18,14 @@ struct header_iter { 


static struct trace_array *mmio_trace_array;

static bool overrun_detected;

static unsigned long prev_overruns;



static void mmio_reset_data(struct trace_array *tr)

{

	int cpu;



	overrun_detected = false;

	prev_overruns = 0;

	tr->time_start = ftrace_now(tr->cpu);



	for_each_online_cpu(cpu)
@@ -128,16 +130,12 @@ static void mmio_close(struct trace_iterator *iter) 


static unsigned long count_overruns(struct trace_iterator *iter)

{

	int cpu;

	unsigned long cnt = 0;

/* FIXME: */

#if 0

	for_each_online_cpu(cpu) {

		cnt += iter->overrun[cpu];

		iter->overrun[cpu] = 0;

	}

#endif

	(void)cpu;

	unsigned long over = ring_buffer_overruns(iter->tr->buffer);



	if (over > prev_overruns)

		cnt = over - prev_overruns;

	prev_overruns = over;

	return cnt;

}