linux-kernel - [PATCH] drivers/hwmon/coretemp: Fix incorrect hot-removed CPU's core sensor issue

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Date:	Wed, 18 Aug 2010 15:53:45 -0700
From:	"Fenghua Yu" <fenghua.yu@...el.com>
To:	"Rudolf Marek" <r.marek@...embler.cz>,
	"Huaxu Wan" <huaxu.wan@...el.com>, "H Peter Anvin" <hpa@...or.com>,
	"Chen Gong" <gong.chen@...ux.intel.com>,
	"Jean Delvare" <khali@...ux-fr.org>
Cc:	"linux-kernel" <linux-kernel@...r.kernel.org>,
	"lm-sensors" <lm-sensors@...sensors.org>,
	Fenghua Yu <fenghua.yu@...el.com>
Subject: [PATCH] drivers/hwmon/coretemp: Fix incorrect hot-removed CPU's core sensor issue

From: Fenghua Yu <fenghua.yu@...el.com>

In current coretemp driver, when a CPU in dev_list is hot-removed, although its
HT sibling is still running, its core sensor is gone and not available to user
level application any more.

When a CPU is hot-removed, its core sensor should be still available to upper
level application as long as the hot-removed CPU's HT sibling is still running.
A core sensor is invisible to user level only when all of siblings in a core are
hot-removed.

This patch fixes this issue.

Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
---
 drivers/hwmon/coretemp.c |   25 ++++++++++++++++++++++---
 1 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index c070c97..2257cc4 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -418,7 +418,7 @@ struct pdev_entry {
 static LIST_HEAD(pdev_list);
 static DEFINE_MUTEX(pdev_list_mutex);
 
-static int __cpuinit coretemp_device_add(unsigned int cpu)
+static int coretemp_device_add(unsigned int cpu)
 {
 	int err;
 	struct platform_device *pdev;
@@ -483,15 +483,34 @@ exit:
 static void coretemp_device_remove(unsigned int cpu)
 {
 	struct pdev_entry *p, *n;
-	mutex_lock(&pdev_list_mutex);
+#ifdef CONFIG_SMP
+	int s;
+#endif
+
 	list_for_each_entry_safe(p, n, &pdev_list, list) {
 		if (p->cpu == cpu) {
+			mutex_lock(&pdev_list_mutex);
 			platform_device_unregister(p->pdev);
 			list_del(&p->list);
 			kfree(p);
+			mutex_unlock(&pdev_list_mutex);
+
+#ifdef CONFIG_SMP
+			/*
+			 * Add removed CPU's HT sibling to dev_list.
+			 * If there is no sibling available, the core sensor
+			 * is invisiable to user space any more.
+			 */
+			for_each_cpu(s, cpu_sibling_mask(cpu)) {
+				if (s != cpu) {
+					coretemp_device_add(s);
+					break;
+				}
+			}
+#endif
+			return;
 		}
 	}
-	mutex_unlock(&pdev_list_mutex);
 }
 
 static int __cpuinit coretemp_cpu_callback(struct notifier_block *nfb,
-- 
1.6.0.3

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