* Re: [PATCH] x86/hwmon: avoid deadlock on CPU removal in pkgtemp
@ 2010-09-15 0:13 ` Fenghua Yu
0 siblings, 0 replies; 8+ messages in thread
From: Fenghua Yu @ 2010-09-15 0:13 UTC (permalink / raw)
To: Jan Beulich
Cc: khali@linux-fr.org, Yu, Fenghua, lm-sensors@lm-sensors.org,
linux-kernel@vger.kernel.org
On Mon, Sep 13, 2010 at 03:11:05AM -0700, Jan Beulich wrote:
> pkgtemp_device_remove(), holding the list protecting mutex, calls
> pkgtemp_device_add(), which itself wants to acquire the same mutex.
> Holding the mutex over the entire loop body in pkgtemp_device_remove()
> isn't really necessary, as long as the loop gets exited after
> processing the matched CPU.
>
> Once exiting the loop after removing an eventual match, there's no
> need for using the "safe" list iterator anymore.
>
> Signed-off-by: Jan Beulich <jbeulich@novell.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>
>
> ---
> drivers/hwmon/pkgtemp.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> --- linux-2.6.36-rc4/drivers/hwmon/pkgtemp.c 2010-09-13 08:45:03.000000000 +0200
> +++ 2.6.36-rc4-x86-pkgtemp-remove-deadlock/drivers/hwmon/pkgtemp.c 2010-09-03 17:54:30.000000000 +0200
> @@ -339,17 +339,18 @@ exit:
> #ifdef CONFIG_HOTPLUG_CPU
> static void pkgtemp_device_remove(unsigned int cpu)
I already sent a fix patch before. I'll push it to Linus.
Thanks.
-Fenghua
From: Fenghua Yu <fenghua.yu@intel.com>
When a sibling is added to dev_list after a cpu is hot-removed, pdev_list_mutex
has been locked already. But pkgtemp_device_add() tries to lock pdev_list_mutex
again. This is incorrect. The patch fixes this issue.
The patch also removes __cpuinit for pkgtemp_device_add() to avoid section
mismatch warning.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
---
drivers/hwmon/pkgtemp.c | 18 +++++++++++++-----
1 files changed, 13 insertions(+), 5 deletions(-)
diff --git a/drivers/hwmon/pkgtemp.c b/drivers/hwmon/pkgtemp.c
index 74157fc..928a016 100644
--- a/drivers/hwmon/pkgtemp.c
+++ b/drivers/hwmon/pkgtemp.c
@@ -276,7 +276,7 @@ struct pdev_entry {
static LIST_HEAD(pdev_list);
static DEFINE_MUTEX(pdev_list_mutex);
-static int __cpuinit pkgtemp_device_add(unsigned int cpu)
+static int pkgtemp_device_add(unsigned int cpu)
{
int err;
struct platform_device *pdev;
@@ -341,26 +341,34 @@ static void pkgtemp_device_remove(unsigned int cpu)
{
struct pdev_entry *p, *n;
unsigned int i;
- int err;
- mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
if (p->cpu != cpu)
continue;
+ mutex_lock(&pdev_list_mutex);
platform_device_unregister(p->pdev);
list_del(&p->list);
kfree(p);
+ mutex_unlock(&pdev_list_mutex);
+ /*
+ * Select one of removed cpu's siblings to represent sensor
+ * for this package.
+ * If there is no more running sibling in a package, the
+ * package sensor for this package is not available to user
+ * space any more.
+ */
for_each_cpu(i, cpu_core_mask(cpu)) {
+ int err;
+
if (i != cpu) {
err = pkgtemp_device_add(i);
if (!err)
break;
}
}
- break;
+ return;
}
- mutex_unlock(&pdev_list_mutex);
}
static int __cpuinit pkgtemp_cpu_callback(struct notifier_block *nfb,
--
1.6.0.3
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [lm-sensors] [PATCH] x86/hwmon: avoid deadlock on CPU removal
2010-09-15 0:13 ` [PATCH] x86/hwmon: avoid deadlock on CPU removal in pkgtemp Fenghua Yu
@ 2010-09-15 1:59 ` Guenter Roeck
-1 siblings, 0 replies; 8+ messages in thread
From: Guenter Roeck @ 2010-09-15 1:59 UTC (permalink / raw)
To: Fenghua Yu
Cc: Jan Beulich, linux-kernel@vger.kernel.org,
lm-sensors@lm-sensors.org
On Tue, Sep 14, 2010 at 08:13:00PM -0400, Fenghua Yu wrote:
> On Mon, Sep 13, 2010 at 03:11:05AM -0700, Jan Beulich wrote:
> > pkgtemp_device_remove(), holding the list protecting mutex, calls
> > pkgtemp_device_add(), which itself wants to acquire the same mutex.
> > Holding the mutex over the entire loop body in pkgtemp_device_remove()
> > isn't really necessary, as long as the loop gets exited after
> > processing the matched CPU.
> >
> > Once exiting the loop after removing an eventual match, there's no
> > need for using the "safe" list iterator anymore.
> >
> > Signed-off-by: Jan Beulich <jbeulich@novell.com>
> > Cc: Fenghua Yu <fenghua.yu@intel.com>
> >
> > ---
> > drivers/hwmon/pkgtemp.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > --- linux-2.6.36-rc4/drivers/hwmon/pkgtemp.c 2010-09-13 08:45:03.000000000 +0200
> > +++ 2.6.36-rc4-x86-pkgtemp-remove-deadlock/drivers/hwmon/pkgtemp.c 2010-09-03 17:54:30.000000000 +0200
> > @@ -339,17 +339,18 @@ exit:
> > #ifdef CONFIG_HOTPLUG_CPU
> > static void pkgtemp_device_remove(unsigned int cpu)
>
> I already sent a fix patch before. I'll push it to Linus.
>
Guess it got lost. Re-sending it might have helped, or adding an Acked-by to this patch.
Guenter
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lm-sensors@lm-sensors.org
http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [lm-sensors] [PATCH] x86/hwmon: avoid deadlock on CPU removal in pkgtemp
@ 2010-09-15 1:59 ` Guenter Roeck
0 siblings, 0 replies; 8+ messages in thread
From: Guenter Roeck @ 2010-09-15 1:59 UTC (permalink / raw)
To: Fenghua Yu
Cc: Jan Beulich, linux-kernel@vger.kernel.org,
lm-sensors@lm-sensors.org
On Tue, Sep 14, 2010 at 08:13:00PM -0400, Fenghua Yu wrote:
> On Mon, Sep 13, 2010 at 03:11:05AM -0700, Jan Beulich wrote:
> > pkgtemp_device_remove(), holding the list protecting mutex, calls
> > pkgtemp_device_add(), which itself wants to acquire the same mutex.
> > Holding the mutex over the entire loop body in pkgtemp_device_remove()
> > isn't really necessary, as long as the loop gets exited after
> > processing the matched CPU.
> >
> > Once exiting the loop after removing an eventual match, there's no
> > need for using the "safe" list iterator anymore.
> >
> > Signed-off-by: Jan Beulich <jbeulich@novell.com>
> > Cc: Fenghua Yu <fenghua.yu@intel.com>
> >
> > ---
> > drivers/hwmon/pkgtemp.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > --- linux-2.6.36-rc4/drivers/hwmon/pkgtemp.c 2010-09-13 08:45:03.000000000 +0200
> > +++ 2.6.36-rc4-x86-pkgtemp-remove-deadlock/drivers/hwmon/pkgtemp.c 2010-09-03 17:54:30.000000000 +0200
> > @@ -339,17 +339,18 @@ exit:
> > #ifdef CONFIG_HOTPLUG_CPU
> > static void pkgtemp_device_remove(unsigned int cpu)
>
> I already sent a fix patch before. I'll push it to Linus.
>
Guess it got lost. Re-sending it might have helped, or adding an Acked-by to this patch.
Guenter
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [lm-sensors] [PATCH] x86/hwmon: avoid deadlock on CPU removal
2010-09-15 0:13 ` [PATCH] x86/hwmon: avoid deadlock on CPU removal in pkgtemp Fenghua Yu
@ 2010-09-15 7:35 ` Jan Beulich
-1 siblings, 0 replies; 8+ messages in thread
From: Jan Beulich @ 2010-09-15 7:35 UTC (permalink / raw)
To: Fenghua Yu
Cc: khali@linux-fr.org, lm-sensors@lm-sensors.org,
linux-kernel@vger.kernel.org
>>> On 15.09.10 at 02:13, Fenghua Yu <fenghua.yu@intel.com> wrote:
> From: Fenghua Yu <fenghua.yu@intel.com>
>
> When a sibling is added to dev_list after a cpu is hot-removed,
> pdev_list_mutex
> has been locked already. But pkgtemp_device_add() tries to lock
> pdev_list_mutex
> again. This is incorrect. The patch fixes this issue.
>
> The patch also removes __cpuinit for pkgtemp_device_add() to avoid section
> mismatch warning.
But that the wrong direction of a change - __cpuinit should be added
to pkgtemp_device_remove() instead.
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
> drivers/hwmon/pkgtemp.c | 18 +++++++++++++-----
> 1 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hwmon/pkgtemp.c b/drivers/hwmon/pkgtemp.c
> index 74157fc..928a016 100644
> --- a/drivers/hwmon/pkgtemp.c
> +++ b/drivers/hwmon/pkgtemp.c
> @@ -276,7 +276,7 @@ struct pdev_entry {
> static LIST_HEAD(pdev_list);
> static DEFINE_MUTEX(pdev_list_mutex);
>
> -static int __cpuinit pkgtemp_device_add(unsigned int cpu)
> +static int pkgtemp_device_add(unsigned int cpu)
> {
> int err;
> struct platform_device *pdev;
> @@ -341,26 +341,34 @@ static void pkgtemp_device_remove(unsigned int cpu)
> {
> struct pdev_entry *p, *n;
> unsigned int i;
> - int err;
>
> - mutex_lock(&pdev_list_mutex);
> list_for_each_entry_safe(p, n, &pdev_list, list) {
> if (p->cpu != cpu)
> continue;
>
> + mutex_lock(&pdev_list_mutex);
> platform_device_unregister(p->pdev);
> list_del(&p->list);
> kfree(p);
> + mutex_unlock(&pdev_list_mutex);
While probably not very important, it's nevertheless unclear why you
need to do the kfree() with the mutex held.
Jan
> + /*
> + * Select one of removed cpu's siblings to represent sensor
> + * for this package.
> + * If there is no more running sibling in a package, the
> + * package sensor for this package is not available to user
> + * space any more.
> + */
> for_each_cpu(i, cpu_core_mask(cpu)) {
> + int err;
> +
> if (i != cpu) {
> err = pkgtemp_device_add(i);
> if (!err)
> break;
> }
> }
> - break;
> + return;
> }
> - mutex_unlock(&pdev_list_mutex);
> }
>
> static int __cpuinit pkgtemp_cpu_callback(struct notifier_block *nfb,
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^ permalink raw reply [flat|nested] 8+ messages in thread* Re: [PATCH] x86/hwmon: avoid deadlock on CPU removal in pkgtemp
@ 2010-09-15 7:35 ` Jan Beulich
0 siblings, 0 replies; 8+ messages in thread
From: Jan Beulich @ 2010-09-15 7:35 UTC (permalink / raw)
To: Fenghua Yu
Cc: khali@linux-fr.org, lm-sensors@lm-sensors.org,
linux-kernel@vger.kernel.org
>>> On 15.09.10 at 02:13, Fenghua Yu <fenghua.yu@intel.com> wrote:
> From: Fenghua Yu <fenghua.yu@intel.com>
>
> When a sibling is added to dev_list after a cpu is hot-removed,
> pdev_list_mutex
> has been locked already. But pkgtemp_device_add() tries to lock
> pdev_list_mutex
> again. This is incorrect. The patch fixes this issue.
>
> The patch also removes __cpuinit for pkgtemp_device_add() to avoid section
> mismatch warning.
But that the wrong direction of a change - __cpuinit should be added
to pkgtemp_device_remove() instead.
> Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
> ---
> drivers/hwmon/pkgtemp.c | 18 +++++++++++++-----
> 1 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/hwmon/pkgtemp.c b/drivers/hwmon/pkgtemp.c
> index 74157fc..928a016 100644
> --- a/drivers/hwmon/pkgtemp.c
> +++ b/drivers/hwmon/pkgtemp.c
> @@ -276,7 +276,7 @@ struct pdev_entry {
> static LIST_HEAD(pdev_list);
> static DEFINE_MUTEX(pdev_list_mutex);
>
> -static int __cpuinit pkgtemp_device_add(unsigned int cpu)
> +static int pkgtemp_device_add(unsigned int cpu)
> {
> int err;
> struct platform_device *pdev;
> @@ -341,26 +341,34 @@ static void pkgtemp_device_remove(unsigned int cpu)
> {
> struct pdev_entry *p, *n;
> unsigned int i;
> - int err;
>
> - mutex_lock(&pdev_list_mutex);
> list_for_each_entry_safe(p, n, &pdev_list, list) {
> if (p->cpu != cpu)
> continue;
>
> + mutex_lock(&pdev_list_mutex);
> platform_device_unregister(p->pdev);
> list_del(&p->list);
> kfree(p);
> + mutex_unlock(&pdev_list_mutex);
While probably not very important, it's nevertheless unclear why you
need to do the kfree() with the mutex held.
Jan
> + /*
> + * Select one of removed cpu's siblings to represent sensor
> + * for this package.
> + * If there is no more running sibling in a package, the
> + * package sensor for this package is not available to user
> + * space any more.
> + */
> for_each_cpu(i, cpu_core_mask(cpu)) {
> + int err;
> +
> if (i != cpu) {
> err = pkgtemp_device_add(i);
> if (!err)
> break;
> }
> }
> - break;
> + return;
> }
> - mutex_unlock(&pdev_list_mutex);
> }
>
> static int __cpuinit pkgtemp_cpu_callback(struct notifier_block *nfb,
^ permalink raw reply [flat|nested] 8+ messages in thread