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@xxxxxxxxxxxxxxx > >>>> Signed-off-by: Rhyland Klein <rklein@xxxxxxxxxx> > >>>> --- > >>>> 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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