We have an arch specific callback here already.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/process.c |   12 ++++++++++++
 kernel/sched/idle.c       |   15 ---------------
 2 files changed, 12 insertions(+), 15 deletions(-)

Index: b/arch/x86/kernel/process.c
===================================================================
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -271,6 +271,18 @@ void exit_idle(void)
 }
 #endif
 
+void arch_cpu_idle_prepare(void)
+{
+	/*
+	 * If we're the non-boot CPU, nothing set the stack canary up
+	 * for us. The boot CPU already has it initialized but no harm
+	 * in doing it again. This is a good place for updating it, as
+	 * we wont ever return from this function (so the invalid
+	 * canaries already on the stack wont ever trigger).
+	 */
+	boot_init_stack_canary();
+}
+
 void arch_cpu_idle_enter(void)
 {
 	local_touch_nmi();
Index: b/kernel/sched/idle.c
===================================================================
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -275,21 +275,6 @@ static void cpu_idle_loop(void)
 
 void cpu_startup_entry(enum cpuhp_state state)
 {
-	/*
-	 * This #ifdef needs to die, but it's too late in the cycle to
-	 * make this generic (arm and sh have never invoked the canary
-	 * init for the non boot cpus!). Will be fixed in 3.11
-	 */
-#ifdef CONFIG_X86
-	/*
-	 * If we're the non-boot CPU, nothing set the stack canary up
-	 * for us. The boot CPU already has it initialized but no harm
-	 * in doing it again. This is a good place for updating it, as
-	 * we wont ever return from this function (so the invalid
-	 * canaries already on the stack wont ever trigger).
-	 */
-	boot_init_stack_canary();
-#endif
 	arch_cpu_idle_prepare();
 	cpu_idle_loop();
 }