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From: Yi Yang <yi.y.yang@intel.com>
To: akpm@linux-foundation.org
Cc: torvalds@linux-foundation.org, gregkh@suse.de,
	davej@codemonkey.org.uk, mingo@elte.hu,
	cpufreq@lists.linux.org.uk, linux-pm@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org
Subject: [PATCH 2.6.25-rc1] cpufreq: fix cpufreq policy refcount imbalance
Date: Fri, 15 Feb 2008 07:48:41 +0800	[thread overview]
Message-ID: <1203032921.3897.10.camel@yangyi-dev.bj.intel.com> (raw)
In-Reply-To: <1201043126.3861.5.camel@yangyi-dev.bj.intel.com>

When one cpu is set to offline, the caller process will hang, according to
the trace data, the problem lies in the refcount error in cpufreq driver,
cpufreq_cpu_callback will wait for completion policy->kobj_unregister
which is nerver completed because a refcount error in function
__cpufreq_remove_dev in file driver/cpufreq/cpufreq.c results in not
calling kobject release method.

In driver/cpufreq/cpufreq.c, the refcount of data->kobj isn't 1 when it
will be unregistered, this problem didn't exist in 2.6.24 and earlier.

The root cause is kobject API switch, kobject_init_and_add and kobject_put
replace older kobject_register and kobject_unregister in 2.6.25-rc1,
compared to 2.6.24, kobject_unregister is deleted in function
__cpufreq_remove_dev but it isn't replaced with kobject_put.

This patch adds kobject_put to balance refcount. I noticed Greg suggests
it will fix a power-off issue to remove kobject_get statement block, but i
think that isn't the best way because those code block has existed very long
and it is helpful because the successive statements are invoking relevant
data.


Signed-off-by: Yi Yang <yi.y.yang@intel.com>
---
 cpufreq.c |    5 +++++
 1 file changed, 5 insertions(+)

--- a/drivers/cpufreq/cpufreq.c	2008-02-15 04:41:29.000000000 +0800
+++ b/drivers/cpufreq/cpufreq.c	2008-02-15 06:56:56.000000000 +0800
@@ -1057,12 +1057,17 @@ static int __cpufreq_remove_dev (struct 
 
 	unlock_policy_rwsem_write(cpu);
 
+	/* it matches the previous kobject_get */
 	kobject_put(&data->kobj);
 
 	/* we need to make sure that the underlying kobj is actually
 	 * not referenced anymore by anybody before we proceed with
 	 * unloading.
 	 */
+
+	/* unregister data->kobj, it matches kobject_init_and_add */
+	kobject_put(&data->kobj);
+
 	dprintk("waiting for dropping of refcount\n");
 	wait_for_completion(&data->kobj_unregister);
 	dprintk("wait complete\n");



  parent reply	other threads:[~2008-02-15  9:09 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-04 10:10 [linux-pm][PATCH] base: Change power/wakeup output from "" to "unsupported" if wakeup feature isn't supported by a device Yi Yang
2008-01-04 11:48 ` Pavel Machek
2008-01-04 16:09   ` David Brownell
2008-01-04 16:38     ` Alan Stern
2008-01-04 16:52       ` Olivier Galibert
2008-01-04 17:20         ` Oliver Neukum
2008-01-07  2:00           ` Yi Yang
2008-01-07  1:55         ` Yi Yang
2008-01-07  3:49           ` David Brownell
2008-01-07  1:52       ` Yi Yang
2008-01-07  1:37     ` Yi Yang
2008-01-07  1:57       ` Rafael J. Wysocki
2008-01-07  2:05         ` Yi Yang
2008-01-07 16:46           ` Rafael J. Wysocki
2008-01-07  1:21   ` Yi Yang
2008-01-04 16:31 ` David Brownell
2008-01-07  1:51   ` Yi Yang
2008-01-22 23:05 ` [PATCH 2.6.24-rc8] cpufreq: fix obvious condition statement error Yi Yang
2008-01-28 23:14   ` [PATCH 2.6.24] x86: add sysfs interface for cpuid module Yi Yang
2008-01-29  8:44     ` Sam Ravnborg
2008-01-29 22:22       ` Yi Yang
2008-01-30  7:48         ` Sam Ravnborg
2008-01-29 15:51     ` H. Peter Anvin
2008-01-29 17:52       ` Yi Yang
2008-01-30  6:09         ` H. Peter Anvin
2008-01-29 21:56       ` Yi Yang
2008-01-30  7:17         ` H. Peter Anvin
2008-01-29 22:13           ` Yi Yang
2008-01-30  7:33             ` H. Peter Anvin
2008-01-29 23:41     ` [RFC PATCH 2.6.24] x86: add sysfs interface for cpuid module, try 2 Yi Yang
2008-01-30 17:35       ` H. Peter Anvin
2008-01-31  1:18       ` [PATCH 2.6.24] Add new string functions real_strtoul and change kernel params to use them Yi Yang
2008-01-31 17:03         ` Randy Dunlap
2008-01-31 16:30           ` Yi Yang
2008-02-01  2:47             ` Randy Dunlap
2008-01-31 22:11         ` [PATCH 2.6.24] Add new string functions strict_strto* and convert kernel params to use them, take 2 Yi Yang
2008-02-01  0:02           ` [PATCH 2.6.24] Add new string functions strict_strto* and convert kernel params to use them, take 3 Yi Yang
2008-02-01  7:36           ` [PATCH 2.6.24] Add new string functions strict_strto* and convert kernel params to use them, take 2 Andrew Morton
2008-02-01  7:39           ` Andrew Morton
2008-02-01  7:40           ` Andrew Morton
2008-02-01 16:31     ` [PATCH 2.6.24] x86: add sysfs interface for cpuid module dean gaudet
2008-02-01 17:56       ` H. Peter Anvin
2008-02-01 17:58         ` H. Peter Anvin
2008-02-14 23:44   ` [PATCH 2.6.25-rc1] cpufreq: fix cpufreq policy refcount imbalance Yi Yang
2008-02-14 23:48   ` Yi Yang [this message]
2008-02-15 15:52     ` [linux-pm] " Alan Stern
2008-02-15 18:24       ` Greg KH
2008-02-15 21:01     ` Greg KH
2008-02-25  0:46     ` [PATCH 2.6.25-rc3] cpuidle: fix cpuidle time and usage overflow Yi Yang
2008-02-25 10:15       ` Ingo Molnar
2008-02-25  1:10         ` Yi Yang
2008-03-26  4:46       ` Len Brown

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