Commit 74e7ff8c authored Jul 28, 2009 by Lai Jiangshan Committed by Frederic Weisbecker Jul 28, 2009

tracing: Fix missing function_graph events when we splice_read from trace_pipe



About a half events are missing when we splice_read
from trace_pipe. They are unexpectedly consumed because we ignore
the TRACE_TYPE_NO_CONSUME return value used by the function graph
tracer when it needs to consume the events by itself to walk on
the ring buffer.

The same problem appears with ftrace_dump()

Example of an output before this patch:

1)               |      ktime_get_real() {
1)   2.846 us    |          read_hpet();
1)   4.558 us    |        }
1)   6.195 us    |      }

After this patch:

0)               |      ktime_get_real() {
0)               |        getnstimeofday() {
0)   1.960 us    |          read_hpet();
0)   3.597 us    |        }
0)   5.196 us    |      }

The fix also applies on 2.6.30

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: stable@kernel.org
LKML-Reference: <4A6EEC52.90704@cn.fujitsu.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

parent 38ceb592

kernel/trace/trace.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -3085,6 +3085,7 @@ tracing_fill_pipe_page(size_t rem, struct trace_iterator *iter)
		break;
		}

		if (ret != TRACE_TYPE_NO_CONSUME)
		trace_consume(iter);
		rem -= count;
		if (!find_next_entry_inc(iter)) {
		@@ -4233,7 +4234,10 @@ static void __ftrace_dump(bool disable_tracing)
		iter.pos = -1;

		if (find_next_entry_inc(&iter) != NULL) {
		print_trace_line(&iter);
		int ret;

		ret = print_trace_line(&iter);
		if (ret != TRACE_TYPE_NO_CONSUME)
		trace_consume(&iter);
		}