x86: Merge the x86_32 and x86_64 cpu_idle() functions

Both functions are mostly identical.
The differences are:

- x86_32's cpu_idle() makes use of check_pgt_cache(), which is a
  nop on both x86_32 and x86_64.

- x86_64's cpu_idle() uses enter/__exit_idle/(), on x86_32 these
  function are a nop.

- In contrast to x86_32, x86_64 calls rcu_idle_enter/exit() in
  the innermost loop because idle notifications need RCU.
  Calling these function on x86_32 also in the innermost loop
  does not hurt.

So we can merge both functions.

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: paulmck@linux.vnet.ibm.com
Cc: josh@joshtriplett.org
Cc: tj@kernel.org
Link: http://lkml.kernel.org/r/1332709204-22496-1-git-send-email-richard@nod.at
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 114 insertions, 0 deletions

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 14baf78d5a1f..29309c42b9e5 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -12,6 +12,9 @@
 #include <linux/user-return-notifier.h>
 #include <linux/dmi.h>
 #include <linux/utsname.h>
+#include <linux/stackprotector.h>
+#include <linux/tick.h>
+#include <linux/cpuidle.h>
 #include <trace/events/power.h>
 #include <linux/hw_breakpoint.h>
 #include <asm/cpu.h>
@@ -23,6 +26,24 @@
 #include <asm/i387.h>
 #include <asm/fpu-internal.h>
 #include <asm/debugreg.h>
+#include <asm/nmi.h>
+
+#ifdef CONFIG_X86_64
+static DEFINE_PER_CPU(unsigned char, is_idle);
+static ATOMIC_NOTIFIER_HEAD(idle_notifier);
+
+void idle_notifier_register(struct notifier_block *n)
+{
+        atomic_notifier_chain_register(&idle_notifier, n);
+}
+EXPORT_SYMBOL_GPL(idle_notifier_register);
+
+void idle_notifier_unregister(struct notifier_block *n)
+{
+        atomic_notifier_chain_unregister(&idle_notifier, n);
+}
+EXPORT_SYMBOL_GPL(idle_notifier_unregister);
+#endif
 
 struct kmem_cache *task_xstate_cachep;
 EXPORT_SYMBOL_GPL(task_xstate_cachep);
@@ -371,6 +392,99 @@ static inline int hlt_use_halt(void)
 }
 #endif
 
+#ifndef CONFIG_SMP
+static inline void play_dead(void)
+{
+        BUG();
+}
+#endif
+
+#ifdef CONFIG_X86_64
+void enter_idle(void)
+{
+        percpu_write(is_idle, 1);
+        atomic_notifier_call_chain(&idle_notifier, IDLE_START, NULL);
+}
+
+static void __exit_idle(void)
+{
+        if (x86_test_and_clear_bit_percpu(0, is_idle) == 0)
+                return;
+        atomic_notifier_call_chain(&idle_notifier, IDLE_END, NULL);
+}
+
+/* Called from interrupts to signify idle end */
+void exit_idle(void)
+{
+        /* idle loop has pid 0 */
+        if (current->pid)
+                return;
+        __exit_idle();
+}
+#endif
+
+/*
+ * The idle thread. There's no useful work to be
+ * done, so just try to conserve power and have a
+ * low exit latency (ie sit in a loop waiting for
+ * somebody to say that they'd like to reschedule)
+ */
+void cpu_idle(void)
+{
+        /*
+         * If we're the non-boot CPU, nothing set the stack canary up
+         * for us.  CPU0 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();
+        current_thread_info()->status |= TS_POLLING;
+
+        while (1) {
+                tick_nohz_idle_enter();
+
+                while (!need_resched()) {
+                        rmb();
+
+                        if (cpu_is_offline(smp_processor_id()))
+                                play_dead();
+
+                        /*
+                         * Idle routines should keep interrupts disabled
+                         * from here on, until they go to idle.
+                         * Otherwise, idle callbacks can misfire.
+                         */
+                        local_touch_nmi();
+                        local_irq_disable();
+
+                        enter_idle();
+
+                        /* Don't trace irqs off for idle */
+                        stop_critical_timings();
+
+                        /* enter_idle() needs rcu for notifiers */
+                        rcu_idle_enter();
+
+                        if (cpuidle_idle_call())
+                                pm_idle();
+
+                        rcu_idle_exit();
+                        start_critical_timings();
+
+                        /* In many cases the interrupt that ended idle
+                           has already called exit_idle. But some idle
+                           loops can be woken up without interrupt. */
+                        __exit_idle();
+                }
+
+                tick_nohz_idle_exit();
+                preempt_enable_no_resched();
+                schedule();
+                preempt_disable();
+        }
+}
+
 /*
  * We use this if we don't have any better
  * idle routine..