ftrace: add ftrace_kill_atomic

It has been suggested that I add a way to disable the function tracer
on an oops. This code adds a ftrace_kill_atomic. It is not meant to be
used in normal situations. It will disable the ftrace tracer, but will
not perform the nice shutdown that requires scheduling.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Cc: Steven Rostedt <srostedt@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 3121b95443d9..f368d041e02d 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -89,6 +89,7 @@ void ftrace_enable_daemon(void);
 
 /* totally disable ftrace - can not re-enable after this */
 void ftrace_kill(void);
+void ftrace_kill_atomic(void);
 
 static inline void tracer_disable(void)
 {
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 0f271c45cd02..1359632668a4 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1602,6 +1602,21 @@ core_initcall(ftrace_dynamic_init);
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
 /**
+ * ftrace_kill_atomic - kill ftrace from critical sections
+ *
+ * This function should be used by panic code. It stops ftrace
+ * but in a not so nice way. If you need to simply kill ftrace
+ * from a non-atomic section, use ftrace_kill.
+ */
+void ftrace_kill_atomic(void)
+{
+        ftrace_disabled = 1;
+        ftrace_enabled = 0;
+        ftraced_suspend = -1;
+        clear_ftrace_function();
+}
+
+/**
  * ftrace_kill - totally shutdown ftrace
  *
  * This is a safety measure. If something was detected that seems