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

[Keerthy]

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.zh...@intel.com>
Cc: linux...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Eduardo Valentin <edubez...@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;