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[130.180.211.218]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-3718983a397sm15355626f8f.24.2024.08.21.03.49.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 21 Aug 2024 03:49:31 -0700 (PDT) Message-ID: Date: Wed, 21 Aug 2024 12:49:30 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 02/14] thermal: core: Rearrange checks in thermal_bind_cdev_to_trip() To: "lihuisong (C)" , "Rafael J. Wysocki" Cc: LKML , Lukasz Luba , Zhang Rui , Linux PM References: <2205737.irdbgypaU6@rjwysocki.net> <3324214.44csPzL39Z@rjwysocki.net> <68ed6185-a602-c0fc-721e-b5d68fea83f8@huawei.com> <66bb19a0-00ba-40a5-91ef-73368659b30a@linaro.org> <8744a789-0424-0cc6-7cb1-b7c9b17f56cc@huawei.com> Content-Language: en-US From: Daniel Lezcano In-Reply-To: <8744a789-0424-0cc6-7cb1-b7c9b17f56cc@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 21/08/2024 11:44, lihuisong (C) wrote: > > 在 2024/8/21 17:28, Daniel Lezcano 写道: >> On 21/08/2024 10:49, lihuisong (C) wrote: >> >> [ ... ] >> >>>> -    list_for_each_entry(pos2, &thermal_cdev_list, node) { >>>> -        if (pos2 == cdev) >>>> -            break; >>>> -    } >>>> +    lockdep_assert_held(&thermal_list_lock); >>>> -    if (tz != pos1 || cdev != pos2) >>>> +    if (list_empty(&tz->node) || list_empty(&cdev->node)) >>> The old verification is ensure that tz and cdev already add to >>> thermal_tz_list and thermal_cdev_list，respectively. >>> Namely, tz and cdev are definitely registered and intialized. >>> The check is ok for all untizalized thermal_zone_device and cooling >>> device. >>> But the new verification doesn't seem to do that. >> >> If the tz or the cdev are registered then their "->node" is not empty >> because they are linked with the thermal_list and cdev_list >> >> So either way is browsing the lists to find the tz/cdev or just check >> "->node" is not empty. The latter the faster. > Assume that tz/cdev isn't intiazlized and registered to thermal_tz_list > or thermal_cdev_list. And then directly call this interface. Then there is a bug in the internal code because the thermal_zone_device_register*() and cooling_device_device_register() allocate and initialize those structures. The caller of the function is supposed to use the API provided by the thermal framework. It is not possible to plan every stupid things a driver can do. In this particular case, very likely the kernel will crash immediately which is a sufficient test for me and coercive enough to have the API user to put its code in question ;) -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog