tracing: Open tracer when ftrace_dump_on_oops is used

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.

Link: http://lkml.kernel.org/r/1382554197-16961-1-git-send-email-cody@linux.vnet.ibm.com

Signed-off-by: Cody P Schafer <cody@linux.vnet.ibm.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f9fa42b180e3..eaacd3aab896 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6276,6 +6276,17 @@ 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)