[GIT pull] locking fix for 4.9

[Thomas Gleixner <tglx@linutronix.de>]

Linus,

please pull the latest locking-urgent-for-linus git tree from:

   git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-for-linus

A single fix which prevents newer GCCs from spamming the build output with
overly eager warnings about __builtin_return_address() uses which are
correct.

Thanks,

	tglx

------------------>
Steven Rostedt (1):
      locking/lockdep: Quiet GCC about dangerous __builtin_return_address() operations


 include/linux/ftrace.h |  2 ++
 kernel/Makefile        |  7 +++++++
 kernel/trace/Kconfig   |  1 +
 lib/Kconfig.debug      | 10 ++++++++++
 4 files changed, 20 insertions(+)

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 6f93ac46e7f0..1218b150a6b3 100644
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -714,6 +714,7 @@ static inline void __ftrace_enabled_restore(int enabled)
 #define CALLER_ADDR5 ((unsigned long)ftrace_return_address(5))
 #define CALLER_ADDR6 ((unsigned long)ftrace_return_address(6))
 
+#ifdef CONFIG_USING_GET_LOCK_PARENT_IP
 static inline unsigned long get_lock_parent_ip(void)
 {
 	unsigned long addr = CALLER_ADDR0;
@@ -725,6 +726,7 @@ static inline unsigned long get_lock_parent_ip(void)
 		return addr;
 	return CALLER_ADDR2;
 }
+#endif
 
 #ifdef CONFIG_IRQSOFF_TRACER
   extern void time_hardirqs_on(unsigned long a0, unsigned long a1);
diff --git a/kernel/Makefile b/kernel/Makefile
index e2ec54e2b952..bff8214bf5f6 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -11,6 +11,13 @@ obj-y     = fork.o exec_domain.o panic.o \
 	    notifier.o ksysfs.o cred.o reboot.o \
 	    async.o range.o smpboot.o
 
+# Tracing may do some dangerous __builtin_return_address() operations
+# We know they are dangerous, we don't need gcc telling us that.
+ifdef CONFIG_USING_GET_LOCK_PARENT_IP
+FRAME_CFLAGS := $(call cc-disable-warning,frame-address)
+KBUILD_CFLAGS += $(FRAME_CFLAGS)
+endif
+
 obj-$(CONFIG_MULTIUSER) += groups.o
 
 ifdef CONFIG_FUNCTION_TRACER
diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index ba3326785ca4..ecc0bbc2ca30 100644
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -192,6 +192,7 @@ config PREEMPT_TRACER
 	select RING_BUFFER_ALLOW_SWAP
 	select TRACER_SNAPSHOT
 	select TRACER_SNAPSHOT_PER_CPU_SWAP
+	select USING_GET_LOCK_PARENT_IP
 	help
 	  This option measures the time spent in preemption-off critical
 	  sections, with microsecond accuracy.
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cab7405f48d2..dbc49c48ff53 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -977,6 +977,7 @@ config TIMER_STATS
 config DEBUG_PREEMPT
 	bool "Debug preemptible kernel"
 	depends on DEBUG_KERNEL && PREEMPT && TRACE_IRQFLAGS_SUPPORT
+	select USING_GET_LOCK_PARENT_IP
 	default y
 	help
 	  If you say Y here then the kernel will use a debug variant of the
@@ -1159,8 +1160,17 @@ config LOCK_TORTURE_TEST
 
 endmenu # lock debugging
 
+config USING_GET_LOCK_PARENT_IP
+        bool
+	help
+	  Enables the use of the function get_lock_parent_ip() that
+	  will use __builtin_return_address(n) with n > 0 causing
+	  some gcc warnings. When this is selected, those warnings
+	  will be suppressed.
+
 config TRACE_IRQFLAGS
 	bool
+	select USING_GET_LOCK_PARENT_IP
 	help
 	  Enables hooks to interrupt enabling and disabling for
 	  either tracing or lock debugging.