tracing: stop stack trace on first empty entry

The stack tracer stores eight entries in the ring buffer when an event
traces the stack. The output outputs all eight entries regardless of
how many entries were recorded.

This patch breaks out of the loop when a null entry is discovered.

[ Impact: only print the stack that is recorded ]

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index 8bd9a2c1a46a..489c0e8ada09 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -898,6 +898,8 @@ static enum print_line_t trace_stack_print(struct trace_iterator *iter,
         trace_assign_type(field, iter->ent);
 
         for (i = 0; i < FTRACE_STACK_ENTRIES; i++) {
+                if (!field->caller[i])
+                        break;
                 if (i) {
                         if (!trace_seq_puts(s, " <= "))
                                 goto partial;