[PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0

[PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0

[Rhyland Klein]

Change power_supply_read_temp() to use power_supply_get_property()
so that it will check the use_cnt and ensure it is > 0. The use_cnt
will be incremented at the end of __power_supply_register, so this
will block to case where get_property can be called before the supply
is fully registered. This fixes the issue show in the stack below:

[    1.452598] power_supply_read_temp+0x78/0x80
[    1.458680] thermal_zone_get_temp+0x5c/0x11c
[    1.464765] thermal_zone_device_update+0x34/0xb4
[    1.471195] thermal_zone_device_register+0x87c/0x8cc
[    1.477974] __power_supply_register+0x364/0x424
[    1.484317] power_supply_register_no_ws+0x10/0x18
[    1.490833] bq27xxx_battery_setup+0x10c/0x164
[    1.497003] bq27xxx_battery_i2c_probe+0xd0/0x1b0
[    1.503435] i2c_device_probe+0x174/0x240
[    1.509172] driver_probe_device+0x1fc/0x29c
[    1.515167] __driver_attach+0xa4/0xa8
[    1.520643] bus_for_each_dev+0x58/0x98
[    1.526204] driver_attach+0x20/0x28
[    1.531505] bus_add_driver+0x1c8/0x22c
[    1.537067] driver_register+0x68/0x108
[    1.542630] i2c_register_driver+0x38/0x7c
[    1.548457] bq27xxx_battery_i2c_driver_init+0x18/0x20
[    1.555321] do_one_initcall+0x38/0x12c
[    1.560886] kernel_init_freeable+0x148/0x1ec
[    1.566972] kernel_init+0x10/0xfc
[    1.572101] ret_from_fork+0x10/0x40

Also make the same change to ps_get_max_charge_cntl_limit() and
ps_get_cur_chrage_cntl_limit() to be safe. Lastly, change the return
value of power_supply_get_property() to -EAGAIN from -ENODEV if
use_cnt <= 0.

Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
Cc: stable@vger.kernel.org
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
---
v3:
 - Changed calls to ->get_property() to use common
   power_supply_get_property()
 - reworded description, added "Fixes" line
 - Changed return value of power_supply_get_property() to -EAGAIN

v2:
 - Added cc stable
 - changed return to -EAGAIN in case of use_cnt < 1
 - Removed WARNING
 - return value check added in additional patch:
   https://lkml.org/lkml/2016/6/6/706

 drivers/power/power_supply_core.c | 26 ++++++++++++++++----------
 1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
index 456987c88baa..cccc630bd68e 100644
--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -492,7 +492,7 @@ int power_supply_get_property(struct power_supply *psy,
 			    union power_supply_propval *val)
 {
 	if (atomic_read(&psy->use_cnt) <= 0)
-		return -ENODEV;
+		return -EAGAIN;
 
 	return psy->desc->get_property(psy, psp, val);
 }
@@ -564,12 +564,14 @@ static int power_supply_read_temp(struct thermal_zone_device *tzd,
 	int ret;
 
 	WARN_ON(tzd == NULL);
+
 	psy = tzd->devdata;
-	ret = psy->desc->get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
+	ret = power_supply_get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
+	if (!ret)
+		return ret;
 
 	/* Convert tenths of degree Celsius to milli degree Celsius. */
-	if (!ret)
-		*temp = val.intval * 100;
+	*temp = val.intval * 100;
 
 	return ret;
 }
@@ -612,10 +614,12 @@ static int ps_get_max_charge_cntl_limit(struct thermal_cooling_device *tcd,
 	int ret;
 
 	psy = tcd->devdata;
-	ret = psy->desc->get_property(psy,
-		POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX, &val);
+	ret = power_supply_get_property(psy,
+			POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX, &val);
 	if (!ret)
-		*state = val.intval;
+		return ret;
+
+	*state = val.intval;
 
 	return ret;
 }
@@ -628,10 +632,12 @@ static int ps_get_cur_chrage_cntl_limit(struct thermal_cooling_device *tcd,
 	int ret;
 
 	psy = tcd->devdata;
-	ret = psy->desc->get_property(psy,
-		POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT, &val);
+	ret = power_supply_get_property(psy,
+			POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT, &val);
 	if (!ret)
-		*state = val.intval;
+		return ret;
+
+	*state = val.intval;
 
 	return ret;
 }
-- 
1.9.1

Re: [PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0

[Krzysztof Kozlowski]

On 06/07/2016 10:26 PM, Rhyland Klein wrote:
> Change power_supply_read_temp() to use power_supply_get_property()
> so that it will check the use_cnt and ensure it is > 0. The use_cnt
> will be incremented at the end of __power_supply_register, so this
> will block to case where get_property can be called before the supply
> is fully registered. This fixes the issue show in the stack below:
> 
> [    1.452598] power_supply_read_temp+0x78/0x80
> [    1.458680] thermal_zone_get_temp+0x5c/0x11c
> [    1.464765] thermal_zone_device_update+0x34/0xb4
> [    1.471195] thermal_zone_device_register+0x87c/0x8cc
> [    1.477974] __power_supply_register+0x364/0x424
> [    1.484317] power_supply_register_no_ws+0x10/0x18
> [    1.490833] bq27xxx_battery_setup+0x10c/0x164
> [    1.497003] bq27xxx_battery_i2c_probe+0xd0/0x1b0
> [    1.503435] i2c_device_probe+0x174/0x240
> [    1.509172] driver_probe_device+0x1fc/0x29c
> [    1.515167] __driver_attach+0xa4/0xa8
> [    1.520643] bus_for_each_dev+0x58/0x98
> [    1.526204] driver_attach+0x20/0x28
> [    1.531505] bus_add_driver+0x1c8/0x22c
> [    1.537067] driver_register+0x68/0x108
> [    1.542630] i2c_register_driver+0x38/0x7c
> [    1.548457] bq27xxx_battery_i2c_driver_init+0x18/0x20
> [    1.555321] do_one_initcall+0x38/0x12c
> [    1.560886] kernel_init_freeable+0x148/0x1ec
> [    1.566972] kernel_init+0x10/0xfc
> [    1.572101] ret_from_fork+0x10/0x40
> 
> Also make the same change to ps_get_max_charge_cntl_limit() and
> ps_get_cur_chrage_cntl_limit() to be safe. Lastly, change the return
> value of power_supply_get_property() to -EAGAIN from -ENODEV if
> use_cnt <= 0.
> 
> Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
> Cc: stable@vger.kernel.org
> Signed-off-by: Rhyland Klein <rklein@nvidia.com>
> ---
> v3:
>  - Changed calls to ->get_property() to use common
>    power_supply_get_property()
>  - reworded description, added "Fixes" line
>  - Changed return value of power_supply_get_property() to -EAGAIN
> 
> v2:
>  - Added cc stable
>  - changed return to -EAGAIN in case of use_cnt < 1
>  - Removed WARNING
>  - return value check added in additional patch:
>    https://lkml.org/lkml/2016/6/6/706
> 
>  drivers/power/power_supply_core.c | 26 ++++++++++++++++----------
>  1 file changed, 16 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
> index 456987c88baa..cccc630bd68e 100644
> --- a/drivers/power/power_supply_core.c
> +++ b/drivers/power/power_supply_core.c
> @@ -492,7 +492,7 @@ int power_supply_get_property(struct power_supply *psy,
>  			    union power_supply_propval *val)
>  {
>  	if (atomic_read(&psy->use_cnt) <= 0)
> -		return -ENODEV;
> +		return -EAGAIN;

Wait, no. I was thinking of changing the return value in
power_supply_read_temp() if we really want EAGAIN:
ret = power_supply_get_property(...);
if (ret)
	return -EAGAIN;

On the other hand, here both return values look correct... the call can
be executed too early (not very common) or too late after unbinding the
driver (also kind of specific).

>  
>  	return psy->desc->get_property(psy, psp, val);
>  }
> @@ -564,12 +564,14 @@ static int power_supply_read_temp(struct thermal_zone_device *tzd,
>  	int ret;
>  
>  	WARN_ON(tzd == NULL);
> +
>  	psy = tzd->devdata;
> -	ret = psy->desc->get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
> +	ret = power_supply_get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
> +	if (!ret)
> +		return ret;

I think you wanted reverse:
	if (ret)

>  
>  	/* Convert tenths of degree Celsius to milli degree Celsius. */
> -	if (!ret)
> -		*temp = val.intval * 100;
> +	*temp = val.intval * 100;
>  
>  	return ret;
>  }
> @@ -612,10 +614,12 @@ static int ps_get_max_charge_cntl_limit(struct thermal_cooling_device *tcd,
>  	int ret;
>  
>  	psy = tcd->devdata;
> -	ret = psy->desc->get_property(psy,
> -		POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX, &val);
> +	ret = power_supply_get_property(psy,
> +			POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX, &val);
>  	if (!ret)
> -		*state = val.intval;
> +		return ret;

Wait, again - why are you inverting the logic of 'ret'?

BR,
Krzysztof

> +
> +	*state = val.intval;
>  
>  	return ret;
>  }
> @@ -628,10 +632,12 @@ static int ps_get_cur_chrage_cntl_limit(struct thermal_cooling_device *tcd,
>  	int ret;
>  
>  	psy = tcd->devdata;
> -	ret = psy->desc->get_property(psy,
> -		POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT, &val);
> +	ret = power_supply_get_property(psy,
> +			POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT, &val);
>  	if (!ret)
> -		*state = val.intval;
> +		return ret;
> +
> +	*state = val.intval;
>  
>  	return ret;
>  }
> 

Re: [PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0

[Rhyland Klein]

On 6/8/2016 2:35 AM, Krzysztof Kozlowski wrote:
> On 06/07/2016 10:26 PM, Rhyland Klein wrote:
>> Change power_supply_read_temp() to use power_supply_get_property()
>> so that it will check the use_cnt and ensure it is > 0. The use_cnt
>> will be incremented at the end of __power_supply_register, so this
>> will block to case where get_property can be called before the supply
>> is fully registered. This fixes the issue show in the stack below:
>>
>> [    1.452598] power_supply_read_temp+0x78/0x80
>> [    1.458680] thermal_zone_get_temp+0x5c/0x11c
>> [    1.464765] thermal_zone_device_update+0x34/0xb4
>> [    1.471195] thermal_zone_device_register+0x87c/0x8cc
>> [    1.477974] __power_supply_register+0x364/0x424
>> [    1.484317] power_supply_register_no_ws+0x10/0x18
>> [    1.490833] bq27xxx_battery_setup+0x10c/0x164
>> [    1.497003] bq27xxx_battery_i2c_probe+0xd0/0x1b0
>> [    1.503435] i2c_device_probe+0x174/0x240
>> [    1.509172] driver_probe_device+0x1fc/0x29c
>> [    1.515167] __driver_attach+0xa4/0xa8
>> [    1.520643] bus_for_each_dev+0x58/0x98
>> [    1.526204] driver_attach+0x20/0x28
>> [    1.531505] bus_add_driver+0x1c8/0x22c
>> [    1.537067] driver_register+0x68/0x108
>> [    1.542630] i2c_register_driver+0x38/0x7c
>> [    1.548457] bq27xxx_battery_i2c_driver_init+0x18/0x20
>> [    1.555321] do_one_initcall+0x38/0x12c
>> [    1.560886] kernel_init_freeable+0x148/0x1ec
>> [    1.566972] kernel_init+0x10/0xfc
>> [    1.572101] ret_from_fork+0x10/0x40
>>
>> Also make the same change to ps_get_max_charge_cntl_limit() and
>> ps_get_cur_chrage_cntl_limit() to be safe. Lastly, change the return
>> value of power_supply_get_property() to -EAGAIN from -ENODEV if
>> use_cnt <= 0.
>>
>> Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Rhyland Klein <rklein@nvidia.com>
>> ---
>> v3:
>>  - Changed calls to ->get_property() to use common
>>    power_supply_get_property()
>>  - reworded description, added "Fixes" line
>>  - Changed return value of power_supply_get_property() to -EAGAIN
>>
>> v2:
>>  - Added cc stable
>>  - changed return to -EAGAIN in case of use_cnt < 1
>>  - Removed WARNING
>>  - return value check added in additional patch:
>>    https://lkml.org/lkml/2016/6/6/706
>>
>>  drivers/power/power_supply_core.c | 26 ++++++++++++++++----------
>>  1 file changed, 16 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
>> index 456987c88baa..cccc630bd68e 100644
>> --- a/drivers/power/power_supply_core.c
>> +++ b/drivers/power/power_supply_core.c
>> @@ -492,7 +492,7 @@ int power_supply_get_property(struct power_supply *psy,
>>  			    union power_supply_propval *val)
>>  {
>>  	if (atomic_read(&psy->use_cnt) <= 0)
>> -		return -ENODEV;
>> +		return -EAGAIN;
> 
> Wait, no. I was thinking of changing the return value in
> power_supply_read_temp() if we really want EAGAIN:
> ret = power_supply_get_property(...);
> if (ret)
> 	return -EAGAIN;
> 
> On the other hand, here both return values look correct... the call can
> be executed too early (not very common) or too late after unbinding the
> driver (also kind of specific).

I did have it that way, but it seemed a little weird to me, since both
situations use the same condition (use_cnt <= 0) to trigger. I don't
think we can differentiate, unless I missed something, so I'm not sure
if it makes sense to override the return value after calling
power_supply_get_property() or not.

If I overrode the return value in get_temp, then assuming it was called
after unbinding, it would return the wrong thing (-EAGAIN). If we want
to support both EAGAIN and ENODEV, then maybe we need to use some
additional check to know which to return from power_supply_get_property().

> 
>>  
>>  	return psy->desc->get_property(psy, psp, val);
>>  }
>> @@ -564,12 +564,14 @@ static int power_supply_read_temp(struct thermal_zone_device *tzd,
>>  	int ret;
>>  
>>  	WARN_ON(tzd == NULL);
>> +
>>  	psy = tzd->devdata;
>> -	ret = psy->desc->get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
>> +	ret = power_supply_get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
>> +	if (!ret)
>> +		return ret;
> 
> I think you wanted reverse:
> 	if (ret)
> 

Indeed.

>>  
>>  	/* Convert tenths of degree Celsius to milli degree Celsius. */
>> -	if (!ret)
>> -		*temp = val.intval * 100;
>> +	*temp = val.intval * 100;
>>  
>>  	return ret;
>>  }
>> @@ -612,10 +614,12 @@ static int ps_get_max_charge_cntl_limit(struct thermal_cooling_device *tcd,
>>  	int ret;
>>  
>>  	psy = tcd->devdata;
>> -	ret = psy->desc->get_property(psy,
>> -		POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX, &val);
>> +	ret = power_supply_get_property(psy,
>> +			POWER_SUPPLY_PROP_CHARGE_CONTROL_LIMIT_MAX, &val);
>>  	if (!ret)
>> -		*state = val.intval;
>> +		return ret;
> 
> Wait, again - why are you inverting the logic of 'ret'?a
> 

copy/paste error repeated... <sigh>

-rhyland
-- 
nvpublic

Re: [PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0

[Krzysztof Kozlowski]

On 06/08/2016 05:26 PM, Rhyland Klein wrote:
> On 6/8/2016 2:35 AM, Krzysztof Kozlowski wrote:
>> On 06/07/2016 10:26 PM, Rhyland Klein wrote:
>>> Change power_supply_read_temp() to use power_supply_get_property()
>>> so that it will check the use_cnt and ensure it is > 0. The use_cnt
>>> will be incremented at the end of __power_supply_register, so this
>>> will block to case where get_property can be called before the supply
>>> is fully registered. This fixes the issue show in the stack below:
>>>
>>> [    1.452598] power_supply_read_temp+0x78/0x80
>>> [    1.458680] thermal_zone_get_temp+0x5c/0x11c
>>> [    1.464765] thermal_zone_device_update+0x34/0xb4
>>> [    1.471195] thermal_zone_device_register+0x87c/0x8cc
>>> [    1.477974] __power_supply_register+0x364/0x424
>>> [    1.484317] power_supply_register_no_ws+0x10/0x18
>>> [    1.490833] bq27xxx_battery_setup+0x10c/0x164
>>> [    1.497003] bq27xxx_battery_i2c_probe+0xd0/0x1b0
>>> [    1.503435] i2c_device_probe+0x174/0x240
>>> [    1.509172] driver_probe_device+0x1fc/0x29c
>>> [    1.515167] __driver_attach+0xa4/0xa8
>>> [    1.520643] bus_for_each_dev+0x58/0x98
>>> [    1.526204] driver_attach+0x20/0x28
>>> [    1.531505] bus_add_driver+0x1c8/0x22c
>>> [    1.537067] driver_register+0x68/0x108
>>> [    1.542630] i2c_register_driver+0x38/0x7c
>>> [    1.548457] bq27xxx_battery_i2c_driver_init+0x18/0x20
>>> [    1.555321] do_one_initcall+0x38/0x12c
>>> [    1.560886] kernel_init_freeable+0x148/0x1ec
>>> [    1.566972] kernel_init+0x10/0xfc
>>> [    1.572101] ret_from_fork+0x10/0x40
>>>
>>> Also make the same change to ps_get_max_charge_cntl_limit() and
>>> ps_get_cur_chrage_cntl_limit() to be safe. Lastly, change the return
>>> value of power_supply_get_property() to -EAGAIN from -ENODEV if
>>> use_cnt <= 0.
>>>
>>> Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
>>> Cc: stable@vger.kernel.org
>>> Signed-off-by: Rhyland Klein <rklein@nvidia.com>
>>> ---
>>> v3:
>>>  - Changed calls to ->get_property() to use common
>>>    power_supply_get_property()
>>>  - reworded description, added "Fixes" line
>>>  - Changed return value of power_supply_get_property() to -EAGAIN
>>>
>>> v2:
>>>  - Added cc stable
>>>  - changed return to -EAGAIN in case of use_cnt < 1
>>>  - Removed WARNING
>>>  - return value check added in additional patch:
>>>    https://lkml.org/lkml/2016/6/6/706
>>>
>>>  drivers/power/power_supply_core.c | 26 ++++++++++++++++----------
>>>  1 file changed, 16 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
>>> index 456987c88baa..cccc630bd68e 100644
>>> --- a/drivers/power/power_supply_core.c
>>> +++ b/drivers/power/power_supply_core.c
>>> @@ -492,7 +492,7 @@ int power_supply_get_property(struct power_supply *psy,
>>>  			    union power_supply_propval *val)
>>>  {
>>>  	if (atomic_read(&psy->use_cnt) <= 0)
>>> -		return -ENODEV;
>>> +		return -EAGAIN;
>>
>> Wait, no. I was thinking of changing the return value in
>> power_supply_read_temp() if we really want EAGAIN:
>> ret = power_supply_get_property(...);
>> if (ret)
>> 	return -EAGAIN;
>>
>> On the other hand, here both return values look correct... the call can
>> be executed too early (not very common) or too late after unbinding the
>> driver (also kind of specific).
> 
> I did have it that way, but it seemed a little weird to me, since both
> situations use the same condition (use_cnt <= 0) to trigger. I don't
> think we can differentiate, unless I missed something, so I'm not sure
> if it makes sense to override the return value after calling
> power_supply_get_property() or not.
> 
> If I overrode the return value in get_temp, then assuming it was called
> after unbinding, it would return the wrong thing (-EAGAIN). If we want
> to support both EAGAIN and ENODEV, then maybe we need to use some
> additional check to know which to return from power_supply_get_property().

Right, currently it is not possible to differentiate these two cases.
After quick look, I think the difference with EAGAIN would be only in
error message printed or not. It is not critical so maybe keep it with
ENODEV?

Best regards,
Krzysztof

Re: [PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0

[Rhyland Klein]

On 6/9/2016 6:05 AM, Krzysztof Kozlowski wrote:
> On 06/08/2016 05:26 PM, Rhyland Klein wrote:
>> On 6/8/2016 2:35 AM, Krzysztof Kozlowski wrote:
>>> On 06/07/2016 10:26 PM, Rhyland Klein wrote:
>>>> Change power_supply_read_temp() to use power_supply_get_property()
>>>> so that it will check the use_cnt and ensure it is > 0. The use_cnt
>>>> will be incremented at the end of __power_supply_register, so this
>>>> will block to case where get_property can be called before the supply
>>>> is fully registered. This fixes the issue show in the stack below:
>>>>
>>>> [    1.452598] power_supply_read_temp+0x78/0x80
>>>> [    1.458680] thermal_zone_get_temp+0x5c/0x11c
>>>> [    1.464765] thermal_zone_device_update+0x34/0xb4
>>>> [    1.471195] thermal_zone_device_register+0x87c/0x8cc
>>>> [    1.477974] __power_supply_register+0x364/0x424
>>>> [    1.484317] power_supply_register_no_ws+0x10/0x18
>>>> [    1.490833] bq27xxx_battery_setup+0x10c/0x164
>>>> [    1.497003] bq27xxx_battery_i2c_probe+0xd0/0x1b0
>>>> [    1.503435] i2c_device_probe+0x174/0x240
>>>> [    1.509172] driver_probe_device+0x1fc/0x29c
>>>> [    1.515167] __driver_attach+0xa4/0xa8
>>>> [    1.520643] bus_for_each_dev+0x58/0x98
>>>> [    1.526204] driver_attach+0x20/0x28
>>>> [    1.531505] bus_add_driver+0x1c8/0x22c
>>>> [    1.537067] driver_register+0x68/0x108
>>>> [    1.542630] i2c_register_driver+0x38/0x7c
>>>> [    1.548457] bq27xxx_battery_i2c_driver_init+0x18/0x20
>>>> [    1.555321] do_one_initcall+0x38/0x12c
>>>> [    1.560886] kernel_init_freeable+0x148/0x1ec
>>>> [    1.566972] kernel_init+0x10/0xfc
>>>> [    1.572101] ret_from_fork+0x10/0x40
>>>>
>>>> Also make the same change to ps_get_max_charge_cntl_limit() and
>>>> ps_get_cur_chrage_cntl_limit() to be safe. Lastly, change the return
>>>> value of power_supply_get_property() to -EAGAIN from -ENODEV if
>>>> use_cnt <= 0.
>>>>
>>>> Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
>>>> Cc: stable@vger.kernel.org
>>>> Signed-off-by: Rhyland Klein <rklein@nvidia.com>
>>>> ---
>>>> v3:
>>>>  - Changed calls to ->get_property() to use common
>>>>    power_supply_get_property()
>>>>  - reworded description, added "Fixes" line
>>>>  - Changed return value of power_supply_get_property() to -EAGAIN
>>>>
>>>> v2:
>>>>  - Added cc stable
>>>>  - changed return to -EAGAIN in case of use_cnt < 1
>>>>  - Removed WARNING
>>>>  - return value check added in additional patch:
>>>>    https://lkml.org/lkml/2016/6/6/706
>>>>
>>>>  drivers/power/power_supply_core.c | 26 ++++++++++++++++----------
>>>>  1 file changed, 16 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
>>>> index 456987c88baa..cccc630bd68e 100644
>>>> --- a/drivers/power/power_supply_core.c
>>>> +++ b/drivers/power/power_supply_core.c
>>>> @@ -492,7 +492,7 @@ int power_supply_get_property(struct power_supply *psy,
>>>>  			    union power_supply_propval *val)
>>>>  {
>>>>  	if (atomic_read(&psy->use_cnt) <= 0)
>>>> -		return -ENODEV;
>>>> +		return -EAGAIN;
>>>
>>> Wait, no. I was thinking of changing the return value in
>>> power_supply_read_temp() if we really want EAGAIN:
>>> ret = power_supply_get_property(...);
>>> if (ret)
>>> 	return -EAGAIN;
>>>
>>> On the other hand, here both return values look correct... the call can
>>> be executed too early (not very common) or too late after unbinding the
>>> driver (also kind of specific).
>>
>> I did have it that way, but it seemed a little weird to me, since both
>> situations use the same condition (use_cnt <= 0) to trigger. I don't
>> think we can differentiate, unless I missed something, so I'm not sure
>> if it makes sense to override the return value after calling
>> power_supply_get_property() or not.
>>
>> If I overrode the return value in get_temp, then assuming it was called
>> after unbinding, it would return the wrong thing (-EAGAIN). If we want
>> to support both EAGAIN and ENODEV, then maybe we need to use some
>> additional check to know which to return from power_supply_get_property().
> 
> Right, currently it is not possible to differentiate these two cases.
> After quick look, I think the difference with EAGAIN would be only in
> error message printed or not. It is not critical so maybe keep it with
> ENODEV?

I'm ok with that. Sebastian, are you ok with that? If so, I'll post a v4
without the -EAGAIN change.

-rhyland

> 
> Best regards,
> Krzysztof
> 


-- 
nvpublic

Re: [PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0

[Sebastian Reichel]

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Hi,

On Thu, Jun 09, 2016 at 11:31:37AM -0400, Rhyland Klein wrote:
> On 6/9/2016 6:05 AM, Krzysztof Kozlowski wrote:
> > On 06/08/2016 05:26 PM, Rhyland Klein wrote:
> >> On 6/8/2016 2:35 AM, Krzysztof Kozlowski wrote:
> >>> On 06/07/2016 10:26 PM, Rhyland Klein wrote:
> >>>> Change power_supply_read_temp() to use power_supply_get_property()
> >>>> so that it will check the use_cnt and ensure it is > 0. The use_cnt
> >>>> will be incremented at the end of __power_supply_register, so this
> >>>> will block to case where get_property can be called before the supply
> >>>> is fully registered. This fixes the issue show in the stack below:
> >>>>
> >>>> [    1.452598] power_supply_read_temp+0x78/0x80
> >>>> [    1.458680] thermal_zone_get_temp+0x5c/0x11c
> >>>> [    1.464765] thermal_zone_device_update+0x34/0xb4
> >>>> [    1.471195] thermal_zone_device_register+0x87c/0x8cc
> >>>> [    1.477974] __power_supply_register+0x364/0x424
> >>>> [    1.484317] power_supply_register_no_ws+0x10/0x18
> >>>> [    1.490833] bq27xxx_battery_setup+0x10c/0x164
> >>>> [    1.497003] bq27xxx_battery_i2c_probe+0xd0/0x1b0
> >>>> [    1.503435] i2c_device_probe+0x174/0x240
> >>>> [    1.509172] driver_probe_device+0x1fc/0x29c
> >>>> [    1.515167] __driver_attach+0xa4/0xa8
> >>>> [    1.520643] bus_for_each_dev+0x58/0x98
> >>>> [    1.526204] driver_attach+0x20/0x28
> >>>> [    1.531505] bus_add_driver+0x1c8/0x22c
> >>>> [    1.537067] driver_register+0x68/0x108
> >>>> [    1.542630] i2c_register_driver+0x38/0x7c
> >>>> [    1.548457] bq27xxx_battery_i2c_driver_init+0x18/0x20
> >>>> [    1.555321] do_one_initcall+0x38/0x12c
> >>>> [    1.560886] kernel_init_freeable+0x148/0x1ec
> >>>> [    1.566972] kernel_init+0x10/0xfc
> >>>> [    1.572101] ret_from_fork+0x10/0x40
> >>>>
> >>>> Also make the same change to ps_get_max_charge_cntl_limit() and
> >>>> ps_get_cur_chrage_cntl_limit() to be safe. Lastly, change the return
> >>>> value of power_supply_get_property() to -EAGAIN from -ENODEV if
> >>>> use_cnt <= 0.
> >>>>
> >>>> Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")
> >>>> Cc: stable@vger.kernel.org
> >>>> Signed-off-by: Rhyland Klein <rklein@nvidia.com>
> >>>> ---
> >>>> v3:
> >>>>  - Changed calls to ->get_property() to use common
> >>>>    power_supply_get_property()
> >>>>  - reworded description, added "Fixes" line
> >>>>  - Changed return value of power_supply_get_property() to -EAGAIN
> >>>>
> >>>> v2:
> >>>>  - Added cc stable
> >>>>  - changed return to -EAGAIN in case of use_cnt < 1
> >>>>  - Removed WARNING
> >>>>  - return value check added in additional patch:
> >>>>    https://lkml.org/lkml/2016/6/6/706
> >>>>
> >>>>  drivers/power/power_supply_core.c | 26 ++++++++++++++++----------
> >>>>  1 file changed, 16 insertions(+), 10 deletions(-)
> >>>>
> >>>> diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
> >>>> index 456987c88baa..cccc630bd68e 100644
> >>>> --- a/drivers/power/power_supply_core.c
> >>>> +++ b/drivers/power/power_supply_core.c
> >>>> @@ -492,7 +492,7 @@ int power_supply_get_property(struct power_supply *psy,
> >>>>  			    union power_supply_propval *val)
> >>>>  {
> >>>>  	if (atomic_read(&psy->use_cnt) <= 0)
> >>>> -		return -ENODEV;
> >>>> +		return -EAGAIN;
> >>>
> >>> Wait, no. I was thinking of changing the return value in
> >>> power_supply_read_temp() if we really want EAGAIN:
> >>> ret = power_supply_get_property(...);
> >>> if (ret)
> >>> 	return -EAGAIN;
> >>>
> >>> On the other hand, here both return values look correct... the call can
> >>> be executed too early (not very common) or too late after unbinding the
> >>> driver (also kind of specific).
> >>
> >> I did have it that way, but it seemed a little weird to me, since both
> >> situations use the same condition (use_cnt <= 0) to trigger. I don't
> >> think we can differentiate, unless I missed something, so I'm not sure
> >> if it makes sense to override the return value after calling
> >> power_supply_get_property() or not.
> >>
> >> If I overrode the return value in get_temp, then assuming it was called
> >> after unbinding, it would return the wrong thing (-EAGAIN). If we want
> >> to support both EAGAIN and ENODEV, then maybe we need to use some
> >> additional check to know which to return from power_supply_get_property().
> > 
> > Right, currently it is not possible to differentiate these two cases.
> > After quick look, I think the difference with EAGAIN would be only in
> > error message printed or not. It is not critical so maybe keep it with
> > ENODEV?
> 
> I'm ok with that. Sebastian, are you ok with that? If so, I'll post a v4
> without the -EAGAIN change.

Yes.

-- Sebastian

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