trace: add a way to enable or disable the stack tracer

Impact: enhancement to stack tracer

The stack tracer currently is either on when configured in or
off when it is not. It can not be disabled when it is configured on.
(besides disabling the function tracer that it uses)

This patch adds a way to enable or disable the stack tracer at
run time. It defaults off on bootup, but a kernel parameter 'stacktrace'
has been added to enable it on bootup.

A new sysctl has been added "kernel.stack_tracer_enabled" to let
the user enable or disable the stack tracer at run time.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 0 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index c83f566e940a..6ac501a2dcc6 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -487,6 +487,16 @@ static struct ctl_table kern_table[] = {
                 .proc_handler   = &ftrace_enable_sysctl,
         },
 #endif
+#ifdef CONFIG_STACK_TRACER
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "stack_tracer_enabled",
+                .data           = &stack_tracer_enabled,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &stack_trace_sysctl,
+        },
+#endif
 #ifdef CONFIG_TRACING
         {
                 .ctl_name       = CTL_UNNUMBERED,