linux-kernel - [PATCH 2.6.25-rc3] processor_idle: fixed CPU 'active state' stably remain C0 by cat /proc

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Date:	Fri, 29 Feb 2008 01:42:17 -0800 (PST)
From:	youquan_song@...ux.intel.com
To:	linux-kernel@...r.kernel.org
Cc:	youquan.song@...el.com
Subject: [PATCH 2.6.25-rc3] processor_idle: fixed CPU 'active state' stably 
     remain C0 by cat /proc

If cpuidle module is enabled by CONFIG_CPU_IDEL=y,user can check CPU idle
information by both /proc and /sys. The two interface keep consistent
except 'active state'. enabling cpuidle will not record CPU active  state
any more, so if we run 'cat /proc/acpi/processor/CPU*/power', we will get
the 'active state' stably remain C0. This is different from user
experience and the case that cpuidle disable by CONFIG_CPU_IDLE=n.

This patch will fix the bug by record the specail C state when CPU is
going to enter to C state. we run 'cat /proc/acpi/processor/CPU*/power'
and we will watch the CPU 'active state' change keeping the same with the
cpu real work.

Signed-off-by: Youquan Song <youquan.song@...el.com>
---
 processor_idle.c |    6 ++++++
 1 file changed, 6 insertions(+)

diff -urNa linux-2.6.25-rc3-orginal/drivers/acpi/processor_idle.c
linux-2.6.25-rc3/drivers/acpi/processor_idle.c
--- linux-2.6.25-rc3-orginal/drivers/acpi/processor_idle.c	2008-02-29
07:58:51.000000000 -0500
+++ linux-2.6.25-rc3/drivers/acpi/processor_idle.c	2008-02-29
11:56:39.000000000 -0500
@@ -1425,6 +1425,8 @@
 		return 0;

 	local_irq_disable();
+	/* Record the active C state */
+	pr->power.state = cx;

 	/* Do not access any ACPI IO ports in suspend path */
 	if (acpi_idle_suspend) {
@@ -1468,6 +1470,8 @@
 		return(acpi_idle_enter_c1(dev, state));

 	local_irq_disable();
+	/* Record the active C state */
+	pr->power.state = cx;
 	current_thread_info()->status &= ~TS_POLLING;
 	/*
 	 * TS_POLLING-cleared state must be visible before we test
@@ -1558,6 +1562,8 @@
 	}

 	local_irq_disable();
+	/* Record the active C state */
+	pr->power.state = cx;
 	current_thread_info()->status &= ~TS_POLLING;
 	/*
 	 * TS_POLLING-cleared state must be visible before we test
--
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