Re: [RESEND PATCH v2] power_supply: power_supply_read_temp only if use_cnt > 0

Krzysztof Kozlowski
2016-06-07T07:23:08Z

On 06/06/2016 06:56 PM, Rhyland Klein wrote:
> Add check to power_supply_read_temp() to only use the power_supply
> get_property() callback if the use_cnt 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
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Rhyland Klein <rklein@nvidia.com>

And maybe:
Fixes: 297d716f6260 ("power_supply: Change ownership from driver to core")

> ---
> v2:
> - Added cc stable
> - changed return to -EAGAIN in case of use_cnt < 1
> - Removed WARNING
> - return value check added in additional patch:
> "thermal: helpers: Check return value of get_temp"
>
> drivers/power/power_supply_core.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
> index 456987c88baa..bbd80631f31e 100644
> --- a/drivers/power/power_supply_core.c
> +++ b/drivers/power/power_supply_core.c
> @@ -561,11 +561,15 @@ static int power_supply_read_temp(struct thermal_zone_device *tzd,
> {
> struct power_supply *psy;
> union power_supply_propval val;
> - int ret;
> + int ret = -EAGAIN;
>
> WARN_ON(tzd == NULL);
> +
> psy = tzd->devdata;
> - ret = psy->desc->get_property(psy, POWER_SUPPLY_PROP_TEMP, &val);
> +
> + if (atomic_read(&psy->use_cnt) > 0)
> + ret = psy->desc->get_property(psy, POWER_SUPPLY_PROP_TEMP,
> + &val);

How about using just power_supply_get_property() and convert return
value to EAGAIN?

Anyway probably such check should be present also on other
get_property() calls, like thermal cooling path.

Best regards,
Krzysztof