[PATCH] ftrace: open tracer when ftrace_dump_on_oops is used

[Cody P Schafer <cody@linux.vnet.ibm.com>]

With ftrace_dump_on_oops, we previously did not open the tracer in
question, sometimes causing the trace output to be useless.

For example, the function_graph tracer with tracing_thresh set dumped via ftrace_dump_on_oops
would show a series of '}' indented at different levels, but no function
names.

call trace->open() (and do a few other fixups copied from the normal dump
path) to make the output more intelligible.

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
---
 kernel/trace/trace.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 7974ba2..18a1b61 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6253,6 +6253,17 @@ void trace_init_global_iter(struct trace_iterator *iter)
 	iter->trace = iter->tr->current_trace;
 	iter->cpu_file = RING_BUFFER_ALL_CPUS;
 	iter->trace_buffer = &global_trace.trace_buffer;
+
+	if (iter->trace && iter->trace->open)
+		iter->trace->open(iter);
+
+	/* Annotate start of buffers if we had overruns */
+	if (ring_buffer_overruns(iter->trace_buffer->buffer))
+		iter->iter_flags |= TRACE_FILE_ANNOTATE;
+
+	/* Output in nanoseconds only if we are using a clock in nanoseconds. */
+	if (trace_clocks[iter->tr->clock_id].in_ns)
+		iter->iter_flags |= TRACE_FILE_TIME_IN_NS;
 }
 
 void ftrace_dump(enum ftrace_dump_mode oops_dump_mode)
-- 
1.8.1.5