linux-kernel - [PATCH -v3 6/7] kexec jump: __ftrace_enabled

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Date:	Tue, 12 Aug 2008 11:14:36 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Steven Rostedt <rostedt@...dmis.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>, mingo@...e.hu,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: [PATCH -v3 6/7] 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@...el.com>

---
 include/linux/ftrace.h |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

--- 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))


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