kexec jump: __ftrace_enabled_save/restore

Add __ftrace_enabled_save/restore, used to disable ftrace for a while.
Now, this is used by kexec jump, which need a version without lock, for
general situation, a locked version should be used.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: Pavel Machek <pavel@ucw.cz>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 21 insertions, 0 deletions

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index f368d041e02d..bb384068272e 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -98,6 +98,27 @@ static inline void tracer_disable(void)
 #endif
 }
 
+/* Ftrace disable/restore without lock. Some synchronization mechanism
+ * must be used to prevent ftrace_enabled to be changed between
+ * disable/restore. */
+static inline int __ftrace_enabled_save(void)
+{
+#ifdef CONFIG_FTRACE
+        int saved_ftrace_enabled = ftrace_enabled;
+        ftrace_enabled = 0;
+        return saved_ftrace_enabled;
+#else
+        return 0;
+#endif
+}
+
+static inline void __ftrace_enabled_restore(int enabled)
+{
+#ifdef CONFIG_FTRACE
+        ftrace_enabled = enabled;
+#endif
+}
+
 #ifdef CONFIG_FRAME_POINTER
 /* TODO: need to fix this for ARM */
 # define CALLER_ADDR0 ((unsigned long)__builtin_return_address(0))