linux-kernel - Re: [PATCH v4] power_supply: power_supply_read_temp only if use

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Date:	Fri, 10 Jun 2016 11:43:24 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Rhyland Klein <rklein@...dia.com>,
	Sebastian Reichel <sre@...nel.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	David Woodhouse <dwmw2@...radead.org>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jon Hunter <jonathanh@...dia.com>, stable@...r.kernel.org
Subject: Re: [PATCH v4] power_supply: power_supply_read_temp only if use_cnt > 0

On 06/09/2016 11:28 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@...r.kernel.org
> Signed-off-by: Rhyland Klein <rklein@...dia.com>
> ---
> v4:
>  - Fixed return check conditions
>  - Removed change to power_supply_get_property return code
>  - removed whitespace change
> 
> 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://patchwork.kernel.org/patch/9158805/
> 
>  drivers/power/power_supply_core.c | 27 ++++++++++++++++-----------
>  1 file changed, 16 insertions(+), 11 deletions(-)

Looks okay:

Reviewed-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

Best regards,
Krzysztof