Re: [PATCH 02/15] thermal: sysfs: lock tz while on access to mode properties

Keerthy
2016-06-07T09:08:32Z

Hi Eduardo,

On Tuesday 31 May 2016 12:01 PM, Eduardo Valentin wrote:
> Serialized calls to tz.ops in user facing
> sysfs handler mode_show() and mode_store().

This seems to be causing a deadlock at boot time during the ending
stages of boot:

http://pastebin.ubuntu.com/17085291/

It took a while to git bisect on linux-next.

Seems like you introduced new locking at the sysfs layer which causes
this deadlock as the underlying code again tries to acquire the same
tz->lock.

Regards,
Keerthy

>
> Cc: Zhang Rui <rui.zhang@intel.com>
> Cc: linux-pm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
> ---
> drivers/thermal/thermal_sysfs.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
> index ee983ca..1db2406 100644
> --- a/drivers/thermal/thermal_sysfs.c
> +++ b/drivers/thermal/thermal_sysfs.c
> @@ -62,7 +62,9 @@ mode_show(struct device *dev, struct device_attribute *attr, char *buf)
> if (!tz->ops->get_mode)
> return -EPERM;
>
> + mutex_lock(&tz->lock);
> result = tz->ops->get_mode(tz, &mode);
> + mutex_unlock(&tz->lock);
> if (result)
> return result;
>
> @@ -75,17 +77,22 @@ mode_store(struct device *dev, struct device_attribute *attr,
> const char *buf, size_t count)
> {
> struct thermal_zone_device *tz = to_thermal_zone(dev);
> + enum thermal_device_mode mode = THERMAL_DEVICE_DISABLED;
> int result;
>
> if (!tz->ops->set_mode)
> return -EPERM;
>
> if (!strncmp(buf, "enabled", sizeof("enabled") - 1))
> - result = tz->ops->set_mode(tz, THERMAL_DEVICE_ENABLED);
> + mode = THERMAL_DEVICE_ENABLED;
> else if (!strncmp(buf, "disabled", sizeof("disabled") - 1))
> - result = tz->ops->set_mode(tz, THERMAL_DEVICE_DISABLED);
> + mode = THERMAL_DEVICE_DISABLED;
> else
> - result = -EINVAL;
> + return -EINVAL;
> +
> + mutex_lock(&tz->lock);
> + result = tz->ops->set_mode(tz, mode);
> + mutex_unlock(&tz->lock);
>
> if (result)
> return result;
>