[patch V5 03/38] nmi, tracing: Provide nmi_enter/exit_notrace()

[Thomas Gleixner <tglx@linutronix.de>]

To fully isolate #DB and #BP from instrumentable code it's necessary to
avoid invoking the hardware latency tracer on nmi_enter/exit().

Provide nmi_enter/exit() variants which are not invoking the hardware
latency tracer. That allows to put calls explicitely into the call sites
outside of the kprobe handling.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
V5: New patch
---
 include/linux/hardirq.h |   18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

--- a/include/linux/hardirq.h
+++ b/include/linux/hardirq.h
@@ -77,28 +77,38 @@ extern void irq_exit(void);
 /*
  * nmi_enter() can nest up to 15 times; see NMI_BITS.
  */
-#define nmi_enter()						\
+#define nmi_enter_notrace()					\
 	do {							\
 		arch_nmi_enter();				\
 		printk_nmi_enter();				\
 		lockdep_off();					\
-		ftrace_nmi_enter();				\
 		BUG_ON(in_nmi() == NMI_MASK);			\
 		__preempt_count_add(NMI_OFFSET + HARDIRQ_OFFSET);	\
 		rcu_nmi_enter();				\
 		lockdep_hardirq_enter();			\
 	} while (0)
 
-#define nmi_exit()						\
+#define nmi_enter()						\
+	do {							\
+		nmi_enter_notrace();				\
+		ftrace_nmi_enter();				\
+	} while (0)
+
+#define nmi_exit_notrace()					\
 	do {							\
 		lockdep_hardirq_exit();				\
 		rcu_nmi_exit();					\
 		BUG_ON(!in_nmi());				\
 		__preempt_count_sub(NMI_OFFSET + HARDIRQ_OFFSET);	\
-		ftrace_nmi_exit();				\
 		lockdep_on();					\
 		printk_nmi_exit();				\
 		arch_nmi_exit();				\
 	} while (0)
 
+#define nmi_exit()						\
+	do {							\
+		ftrace_nmi_exit();				\
+		nmi_exit_notrace();				\
+	} while (0)
+
 #endif /* LINUX_HARDIRQ_H */