ftrace: add ftrace_off_permanent

Impact: add new API to disable all of ftrace on anomalies

It case of a serious anomaly being detected (like something caught by
lockdep) it is a good idea to disable all tracing immediately, without
grabing any locks.

This patch adds ftrace_off_permanent that disables the tracers, function
tracing and ring buffers without a way to enable them again. This should
only be used when something serious has been detected.

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

1 files changed, 15 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 4ee6f0375222..0dbfb23ced97 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -661,6 +661,21 @@ static int trace_stop_count;
 static DEFINE_SPINLOCK(tracing_start_lock);
 
 /**
+ * ftrace_off_permanent - disable all ftrace code permanently
+ *
+ * This should only be called when a serious anomally has
+ * been detected.  This will turn off the function tracing,
+ * ring buffers, and other tracing utilites. It takes no
+ * locks and can be called from any context.
+ */
+void ftrace_off_permanent(void)
+{
+        tracing_disabled = 1;
+        ftrace_stop();
+        tracing_off_permanent();
+}
+
+/**
  * tracing_start - quick start of the tracer
  *
  * If tracing is enabled but was stopped by tracing_stop,