linux-kernel - [PATCH 4.6 031/203] cpuidle: Do not access cpuidle_devices when !CONFIG_CPU

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Date:	Mon, 25 Jul 2016 13:54:06 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Catalin Marinas <catalin.marinas@....com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 4.6 031/203] cpuidle: Do not access cpuidle_devices when !CONFIG_CPU_IDLE

4.6-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Catalin Marinas <catalin.marinas@....com>

commit 9bd616e3dbedfc103f158197c8ad93678849b1ed upstream.

The cpuidle_devices per-CPU variable is only defined when CPU_IDLE is
enabled. Commit c8cc7d4de7a4 ("sched/idle: Reorganize the idle loop")
removed the #ifdef CONFIG_CPU_IDLE around cpuidle_idle_call() with the
compiler optimising away __this_cpu_read(cpuidle_devices). However, with
CONFIG_UBSAN && !CONFIG_CPU_IDLE, this optimisation no longer happens
and the kernel fails to link since cpuidle_devices is not defined.

This patch introduces an accessor function for the current CPU cpuidle
device (returning NULL when !CONFIG_CPU_IDLE) and uses it in
cpuidle_idle_call().

Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/cpuidle.h |    3 +++
 kernel/sched/idle.c     |    2 +-
 2 files changed, 4 insertions(+), 1 deletion(-)

--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -152,6 +152,8 @@ extern void cpuidle_disable_device(struc
 extern int cpuidle_play_dead(void);

 extern struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev);
+static inline struct cpuidle_device *cpuidle_get_device(void)
+{return __this_cpu_read(cpuidle_devices); }
 #else
 static inline void disable_cpuidle(void) { }
 static inline bool cpuidle_not_available(struct cpuidle_driver *drv,
@@ -187,6 +189,7 @@ static inline void cpuidle_disable_devic
 static inline int cpuidle_play_dead(void) {return -ENODEV; }
 static inline struct cpuidle_driver *cpuidle_get_cpu_driver(
 	struct cpuidle_device *dev) {return NULL; }
+static inline struct cpuidle_device *cpuidle_get_device(void) {return NULL; }
 #endif

 #if defined(CONFIG_CPU_IDLE) && defined(CONFIG_SUSPEND)
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -127,7 +127,7 @@ static int call_cpuidle(struct cpuidle_d
  */
 static void cpuidle_idle_call(void)
 {
-	struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices);
+	struct cpuidle_device *dev = cpuidle_get_device();
 	struct cpuidle_driver *drv = cpuidle_get_cpu_driver(dev);
 	int next_state, entered_state;