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, 4 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2919a2e91938..edab81c13182 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -89,6 +89,7 @@ parameter is applicable:
         SPARC   Sparc architecture is enabled.
         SWSUSP  Software suspend (hibernation) is enabled.
         SUSPEND System suspend states are enabled.
+        FTRACE  Function tracing enabled.
         TS      Appropriate touchscreen support is enabled.
         USB     USB support is enabled.
         USBHID  USB Human Interface Device support is enabled.
@@ -2173,6 +2174,9 @@ and is between 256 and 4096 characters. It is defined in the file
         st=             [HW,SCSI] SCSI tape parameters (buffers, etc.)
                         See Documentation/scsi/st.txt.
 
+        stacktrace      [FTRACE]
+                        Enabled the stack tracer on boot up.
+
         sti=            [PARISC,HW]
                         Format: <num>
                         Set the STI (builtin display/keyboard on the HP-PARISC