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Subject[GIT pull] locking fix for 4.9
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.
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