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@xxxxxxxxxx>
> Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
>
> ---
> 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@xxxxxxxxx>
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@xxxxxxxxx>
---
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
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