idle: Provide a generic entry point for the idle code

For now this calls cpu_idle(), but in the long run we want to move the
cpu bringup code to the core and therefor we add a state argument.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Reviewed-by: Cc: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Cc: Magnus Damm <magnus.damm@gmail.com>
Link: http://lkml.kernel.org/r/20130321215233.583190032@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/cpu.h

@@ -212,4 +212,12 @@ static inline int disable_nonboot_cpus(void) { return 0; }
 static inline void enable_nonboot_cpus(void) {}
 #endif /* !CONFIG_PM_SLEEP_SMP */
 
+enum cpuhp_state {
+	CPUHP_OFFLINE,
+	CPUHP_ONLINE,
+};
+
+void cpu_startup_entry(enum cpuhp_state state);
+void cpu_idle(void);
+
 #endif /* _LINUX_CPU_H_ */

init/main.c

@@ -384,7 +384,7 @@ static noinline void __init_refok rest_init(void)
 	init_idle_bootup_task(current);
 	schedule_preempt_disabled();
 	/* Call into cpu_idle with preempt disabled */
-	cpu_idle();
+	cpu_startup_entry(CPUHP_ONLINE);
 }
 
 /* Check for early params. */

kernel/Makefile

@@ -24,6 +24,7 @@ endif
 
 obj-y += sched/
 obj-y += power/
+obj-y += cpu/
 
 obj-$(CONFIG_CHECKPOINT_RESTORE) += kcmp.o
 obj-$(CONFIG_FREEZER) += freezer.o

kernel/cpu/Makefile

@@ -0,0 +1 @@
+obj-y	= idle.o

kernel/cpu/idle.c

@@ -0,0 +1,10 @@
+/*
+ * Generic entry point for the idle threads
+ */
+#include <linux/sched.h>
+#include <linux/cpu.h>
+
+void cpu_startup_entry(enum cpuhp_state state)
+{
+	cpu_idle();
+}