linux-kernel - [for-next][PATCH 18/18] tracing: Have stack tracer trace full stack

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Date:   Sun, 28 Oct 2018 03:30:06 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>
Subject: [for-next][PATCH 18/18] tracing: Have stack tracer trace full stack

From: "Steven Rostedt (VMware)" <rostedt@...dmis.org>

The stack tracer traces every function call checking the current stack (in
non interrupt context), looking for the deepest stack, and saving it when it
finds a new max depth. The problem is that it calls save_stack_trace(), and
with the new ORC unwinder, it can skip too much. As it looks at the ip of
the function call in the backtrace to find where it should start, it doesn't
need to skip anything.

The stack trace selftest would fail when the kernel was complied with the
ORC UNDWINDER enabled. Without skipping functions when doing the stack
trace, it now passes again.

Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 kernel/trace/trace_stack.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_stack.c b/kernel/trace/trace_stack.c
index 4237eba4ef20..2b0d1ee3241c 100644
--- a/kernel/trace/trace_stack.c
+++ b/kernel/trace/trace_stack.c
@@ -111,7 +111,7 @@ check_stack(unsigned long ip, unsigned long *stack)
 	stack_trace_max_size = this_size;

 	stack_trace_max.nr_entries = 0;
-	stack_trace_max.skip = 3;
+	stack_trace_max.skip = 0;

 	save_stack_trace(&stack_trace_max);

-- 
2.19.0