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 <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Vivek Goyal <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Steven Rostedt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index f368d041e02d1f41ccb36bda3a4c5da59c65df3d..bb384068272e1ef5ef9f4aa4a04572e48dcbfca5 100644 (file)
--- 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))