linux-kernel - [RFC PATCH 2/2] Idle notifier standardization x86

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Message-ID: <20100908155953.GB23344@Krystal>
Date:	Wed, 8 Sep 2010 11:59:54 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:	linux-kernel@...r.kernel.org
Cc:	ltt-dev@...ts.casi.polymtl.ca,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Li Zefan <lizf@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Tom Zanussi <tzanussi@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>
Subject: [RFC PATCH 2/2] Idle notifier standardization x86_32 (v2)

Add idle notifier callback to x86_32.

Changelog since v1:
* Add CONFIG_HAVE_IDLE_NOTIFIER.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.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
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