From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752142AbcFIKFj (ORCPT ); Thu, 9 Jun 2016 06:05:39 -0400 Received: from mailout2.w1.samsung.com ([210.118.77.12]:56642 "EHLO mailout2.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750846AbcFIKFa (ORCPT ); Thu, 9 Jun 2016 06:05:30 -0400 X-AuditID: cbfec7f5-f792a6d000001302-fa-57593f66f03d Subject: Re: [PATCH v3] power_supply: power_supply_read_temp only if use_cnt > 0 To: Rhyland Klein , Sebastian Reichel , Dmitry Eremin-Solenikov , David Woodhouse References: <1465331163-16884-1-git-send-email-rklein@nvidia.com> <5757BCAD.4060101@samsung.com> Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, Jon Hunter , stable@vger.kernel.org From: Krzysztof Kozlowski Message-id: <57593F65.2070900@samsung.com> Date: Thu, 09 Jun 2016 12:05:25 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0 MIME-version: 1.0 In-reply-to: Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: 7bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrOLMWRmVeSWpSXmKPExsVy+t/xa7pp9pHhBse+q1pMevKe2WLiysnM Fi2zFrFYvH5haHF51xw2i8+9Rxgtlh1fzWpxeneJxYKNjxgdOD12zrrL7rF5hZbHplWdbB69 ze/YPPq2rGL0+LxJLoAtissmJTUnsyy1SN8ugStjeetRxoKLihWNR5MaGO9LdzFyckgImEjs +3OOCcIWk7hwbz1bFyMXh5DAUkaJm5eWsUM4zxglTpx5BlYlLBAg8f7RcbCEiMASRomfOxoZ IaqmMUoc+PCKHaSKWaBc4s75NhYQm03AWGLz8iVsIDavgJbEqRUvweIsAqoSi08vAZsqKhAh MWv7DyaIGkGJH5PvgdVwCthJTFjeCWRzAM3Uk7h/UQtivLzE5jVvmScwCsxC0jELoWoWkqoF jMyrGEVTS5MLipPSc430ihNzi0vz0vWS83M3MUKC/+sOxqXHrA4xCnAwKvHwaqREhAuxJpYV V+YeYpTgYFYS4f1hHhkuxJuSWFmVWpQfX1Sak1p8iFGag0VJnHfmrvchQgLpiSWp2ampBalF MFkmDk6pBkbxH6+PFyUzq80oCq3iu2H8yvLTZp/0FWYdolM15xz/LqRUnfPTrKfyvLDck+y3 h6Y+WvZHu/aiVneW5otm4c64Ih0hPvfUvGZl8ezAJf+E+Dbt3TaHa2dkfv8CP5+AjkW8gp9O HHY7/3O15KL2hpfzQwsjJzMZtju3BiyaXb7phc6+KZct0pVYijMSDbWYi4oTAU1NKpB6AgAA Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 >>> --- >>> 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