[RFC PATCH 2/2] Idle notifier standardization x86_32 (v2)

[Mathieu Desnoyers <mathieu.desnoyers@efficios.com>]

Add idle notifier callback to x86_32.

Changelog since v1:
* Add CONFIG_HAVE_IDLE_NOTIFIER.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 arch/x86/Kconfig             |    2 +-
 arch/x86/include/asm/idle.h  |    5 -----
 arch/x86/kernel/apm_32.c     |    6 ++++++
 arch/x86/kernel/process_32.c |   33 +++++++++++++++++++++++++++++++++
 4 files changed, 40 insertions(+), 6 deletions(-)

Index: linux.trees.git/arch/x86/kernel/process_32.c
===================================================================
--- linux.trees.git.orig/arch/x86/kernel/process_32.c
+++ linux.trees.git/arch/x86/kernel/process_32.c
@@ -38,6 +38,8 @@
 #include <linux/uaccess.h>
 #include <linux/io.h>
 #include <linux/kdebug.h>
+#include <linux/notifier.h>
+#include <linux/idle.h>
 
 #include <asm/pgtable.h>
 #include <asm/system.h>
@@ -61,6 +63,30 @@
 
 asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
 
+static DEFINE_PER_CPU(unsigned char, is_idle);
+
+void enter_idle(void)
+{
+	percpu_write(is_idle, 1);
+	notify_idle(IDLE_START);
+}
+
+static void __exit_idle(void)
+{
+	if (x86_test_and_clear_bit_percpu(0, is_idle) == 0)
+		return;
+	notify_idle(IDLE_END);
+}
+
+/* Called from interrupts to signify idle end */
+void exit_idle(void)
+{
+	/* idle loop has pid 0 */
+	if (current->pid)
+		return;
+	__exit_idle();
+}
+
 /*
  * Return saved PC of a blocked thread.
  */
@@ -109,10 +135,17 @@ void cpu_idle(void)
 				play_dead();
 
 			local_irq_disable();
+			enter_idle();
 			/* Don't trace irqs off for idle */
 			stop_critical_timings();
 			pm_idle();
 			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();
 
 			trace_power_end(smp_processor_id());
 		}
Index: linux.trees.git/arch/x86/include/asm/idle.h
===================================================================
--- linux.trees.git.orig/arch/x86/include/asm/idle.h
+++ linux.trees.git/arch/x86/include/asm/idle.h
@@ -1,13 +1,8 @@
 #ifndef _ASM_X86_IDLE_H
 #define _ASM_X86_IDLE_H
 
-#ifdef CONFIG_X86_64
 void enter_idle(void);
 void exit_idle(void);
-#else /* !CONFIG_X86_64 */
-static inline void enter_idle(void) { }
-static inline void exit_idle(void) { }
-#endif /* CONFIG_X86_64 */
 
 void c1e_remove_cpu(int cpu);
 
Index: linux.trees.git/arch/x86/kernel/apm_32.c
===================================================================
--- linux.trees.git.orig/arch/x86/kernel/apm_32.c
+++ linux.trees.git/arch/x86/kernel/apm_32.c
@@ -227,6 +227,7 @@
 #include <linux/suspend.h>
 #include <linux/kthread.h>
 #include <linux/jiffies.h>
+#include <linux/idle.h>
 
 #include <asm/system.h>
 #include <asm/uaccess.h>
@@ -947,10 +948,15 @@ recalc:
 				break;
 			}
 		}
+		enter_idle();
 		if (original_pm_idle)
 			original_pm_idle();
 		else
 			default_idle();
+		/* 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();
 		local_irq_disable();
 		jiffies_since_last_check = jiffies - last_jiffies;
 		if (jiffies_since_last_check > idle_period)
Index: linux.trees.git/arch/x86/Kconfig
===================================================================
--- linux.trees.git.orig/arch/x86/Kconfig
+++ linux.trees.git/arch/x86/Kconfig
@@ -45,7 +45,7 @@ config X86
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_GENERIC_DMA_COHERENT if X86_32
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS
-	select HAVE_IDLE_NOTIFIER if X86_64
+	select HAVE_IDLE_NOTIFIER
 	select USER_STACKTRACE_SUPPORT
 	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_DMA_API_DEBUG
-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com