On Fri, Jan 27, 2017 at 09:47:08AM +0100, Miroslav Benes wrote:

quoted

diff --git a/include/linux/stacktrace.h b/include/linux/stacktrace.h
index 0a34489..8e8b67b 100644
--- a/include/linux/stacktrace.h
+++ b/include/linux/stacktrace.h

@@ -18,6 +18,8 @@ extern void save_stack_trace_regs(struct pt_regs *regs,
 				  struct stack_trace *trace);
 extern void save_stack_trace_tsk(struct task_struct *tsk,
 				struct stack_trace *trace);
+extern int save_stack_trace_tsk_reliable(struct task_struct *tsk,
+					 struct stack_trace *trace);
 
 extern void print_stack_trace(struct stack_trace *trace, int spaces);
 extern int snprint_stack_trace(char *buf, size_t size,

@@ -29,12 +31,12 @@ extern void save_stack_trace_user(struct stack_trace *trace);
 # define save_stack_trace_user(trace)              do { } while (0)
 #endif
 
-#else
+#else /* !CONFIG_STACKTRACE */
 # define save_stack_trace(trace)			do { } while (0)
 # define save_stack_trace_tsk(tsk, trace)		do { } while (0)
 # define save_stack_trace_user(trace)			do { } while (0)
 # define print_stack_trace(trace, spaces)		do { } while (0)
 # define snprint_stack_trace(buf, size, trace, spaces)	do { } while (0)

Is there a reason you did not define empty save_stack_trace_tsk_reliable() 
here? Right, it should not be needed now as livepatching is the only user, 
but still.

Agreed, thanks.  I'll make the stub return an error, since an empty
stack trace isn't very reliable.

-- 
Josh