From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from szxga06-in.huawei.com (szxga06-in.huawei.com [45.249.212.32]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 47B41200CD; Wed, 27 Nov 2024 02:29:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=45.249.212.32 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732674589; cv=none; b=U9nIINU4Rp4o2MDyt+MCAoqMDucyHQF++2KD19TRVefmD2TeqDiDeOi6MOFh3Mb70noO0HdKHgsqjGAMroPJ2U/tZd/EdVAJzhg4AME/yvy7mN8bRpEIP/Hh4O2fuBbZqYAcN9OC9jCltg6ILGXliC1NehU3ik64avNvlnYvgCg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732674589; c=relaxed/simple; bh=dGsjBWg8Ef2DD63DqlQFQF227zaA+1OH8lbw87fE2qU=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=D/zA9qKiUIwbF44o++NAcfgCsQgUnkAvRSKmDrBbkh7tW8QUtMdXqZe6v3Ht61QjpiuiZWvy9PQUH6XhSsesmFEc43oOmExTXqcf3ZdE/ob8WzB5zOnuVUmKqIpAz49YC3jL8r9cObU9UihedqAgRylBzm9zfLaNT46fPIH/7Qg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com; spf=pass smtp.mailfrom=huawei.com; arc=none smtp.client-ip=45.249.212.32 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=huawei.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=huawei.com Received: from mail.maildlp.com (unknown [172.19.162.112]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4Xyk1C1Qtwz1yr7q; Wed, 27 Nov 2024 10:29:51 +0800 (CST) Received: from dggemv711-chm.china.huawei.com (unknown [10.1.198.66]) by mail.maildlp.com (Postfix) with ESMTPS id 03142140336; Wed, 27 Nov 2024 10:29:37 +0800 (CST) Received: from kwepemn100009.china.huawei.com (7.202.194.112) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.1.2507.39; Wed, 27 Nov 2024 10:29:36 +0800 Received: from [10.67.121.59] (10.67.121.59) by kwepemn100009.china.huawei.com (7.202.194.112) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.11; Wed, 27 Nov 2024 10:29:36 +0800 Message-ID: <1823a64b-cfd0-de9a-fb0e-5112079b604d@huawei.com> Date: Wed, 27 Nov 2024 10:29:35 +0800 Precedence: bulk X-Mailing-List: linux-hwmon@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH v1 1/4] hwmon: (acpi_power_meter) Fix using uninitialized variables To: Guenter Roeck , , CC: , , , References: <20241125093415.21719-1-lihuisong@huawei.com> <20241125093415.21719-2-lihuisong@huawei.com> <77fce1aa-96eb-4c3c-ab0a-a33de46b333b@roeck-us.net> From: "lihuisong (C)" In-Reply-To: <77fce1aa-96eb-4c3c-ab0a-a33de46b333b@roeck-us.net> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To kwepemn100009.china.huawei.com (7.202.194.112) 在 2024/11/27 0:19, Guenter Roeck 写道: > On 11/25/24 23:03, lihuisong (C) wrote: >> >> 在 2024/11/26 12:04, Guenter Roeck 写道: >>> On 11/25/24 17:56, lihuisong (C) wrote: >>>> Hi Guente, >>>> >>>> Thanks for your timely review. >>>> >>>> 在 2024/11/26 0:03, Guenter Roeck 写道: >>>>> On 11/25/24 01:34, Huisong Li wrote: >>>>>> The 'power1_alarm' attribute uses the 'power' and 'cap' in the >>>>>> acpi_power_meter_resource structure. However, these two fields >>>>>> are just >>>>>> updated when user query 'power' and 'cap' attribute, or hardware >>>>>> enforced >>>>>> limit. If user directly query the 'power1_alarm' attribute >>>>>> without queryng >>>>>> above two attributes, driver will use the uninitialized variables >>>>>> to judge. >>>>>> In addition, the 'power1_alarm' attribute needs to update power >>>>>> and cap to >>>>>> show the real state. >>>>>> >>>>>> Signed-off-by: Huisong Li >>>>>> --- >>>>>>   drivers/hwmon/acpi_power_meter.c | 10 ++++++++++ >>>>>>   1 file changed, 10 insertions(+) >>>>>> >>>>>> diff --git a/drivers/hwmon/acpi_power_meter.c >>>>>> b/drivers/hwmon/acpi_power_meter.c >>>>>> index 2f1c9d97ad21..4c3314e35d30 100644 >>>>>> --- a/drivers/hwmon/acpi_power_meter.c >>>>>> +++ b/drivers/hwmon/acpi_power_meter.c >>>>>> @@ -396,6 +396,9 @@ static ssize_t show_val(struct device *dev, >>>>>>       struct acpi_device *acpi_dev = to_acpi_device(dev); >>>>>>       struct acpi_power_meter_resource *resource = >>>>>> acpi_dev->driver_data; >>>>>>       u64 val = 0; >>>>>> +    int ret; >>>>>> + >>>>>> +    guard(mutex)(&resource->lock); >>>>>>         switch (attr->index) { >>>>>>       case 0: >>>>>> @@ -423,6 +426,13 @@ static ssize_t show_val(struct device *dev, >>>>>>               val = 0; >>>>>>           break; >>>>>>       case 6: >>>>>> +        ret = update_meter(resource); >>>>>> +        if (ret) >>>>>> +            return ret; >>>>>> +        ret = update_cap(resource); >>>>>> +        if (ret) >>>>>> +            return ret; >>>>>> + >>>>>>           if (resource->power > resource->cap) >>>>>>               val = 1; >>>>>>           else >>>>> >>>>> >>>>> While technically correct, the implementation of this attribute >>>>> defeats its >>>>> purpose. It is supposed to reflect the current status as reported >>>>> by the >>>>> hardware. A real fix would be to use the associated notification >>>>> to set or >>>>> reset a status flag, and to report the current value of that flag >>>>> as reported >>>>> by the hardware. >>>> I know what you mean. >>>> The Notify(power_meter, 0x83) is supposed to meet your proposal IIUC. >>>> It's good, but it depands on hardware support notification. >>>>> >>>>> If there is no notification support, the attribute should not even >>>>> exist, >>>>> unless there is a means to retrieve its value from ACPI (the >>>>> status itself, >>>>> not by comparing temperature values). >>>> Currently, the 'power1_alarm' attribute is created just when >>>> platform support the power meter meassurement(bit0 of the supported >>>> capabilities in _PMC). >>>> And it doesn't see if the platform support notifications. >>>>  From the current implementation of this driver, this sysfs can >>>> also reflect the status by comparing power and cap, >>>> which is good to the platform that support hardware limit from some >>>> out-of-band mechanism but doesn't support any notification. >>>> >>> >>> The point is that this can also be done from userspace. Hardware >>> monitoring drivers >>> are supposed to provide hardware attributes, not software attributes >>> derived from it. >>> >> So this 'power1_alarm' attribute can be exposed when platform >> supports hardware enforced limit and notifcations when the hardware >> limit is enforced, right? >> If so, we have to change the condition that driver creates this sysfs >> interface. > > This isn't about enforcing anything, it is about reporting an alarm > if the power consumed exceeds the maximum configured. > Sorry, I don't quite understand what you mean. What your mean is to delete the current 'power1_alarm' sysfs and just use the related notify event to user? How should we fix this issue? /Huisong > > .