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[2001:1c00:c1e:bf00:1054:9d19:e0f0:8214]) by smtp.gmail.com with ESMTPSA id u13sm11189851ejy.31.2021.03.23.06.59.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 23 Mar 2021 06:59:07 -0700 (PDT) Subject: Re: [PATCH v3 1/8] workqueue: Add resource managed version of delayed work init To: Matti Vaittinen , Matti Vaittinen Cc: MyungJoo Ham , Chanwoo Choi , Andy Gross , Bjorn Andersson , Jean Delvare , Guenter Roeck , Mark Gross , Sebastian Reichel , Chen-Yu Tsai , Liam Girdwood , Mark Brown , Wim Van Sebroeck , gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-hwmon@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-pm@vger.kernel.org, linux-watchdog@vger.kernel.org References: <51769ea4668198deb798fe47fcfb5f5288d61586.1616506559.git.matti.vaittinen@fi.rohmeurope.com> From: Hans de Goede Message-ID: <90d2d9ab-f668-d819-4ca3-d893961ea19a@redhat.com> Date: Tue, 23 Mar 2021 14:59:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <51769ea4668198deb798fe47fcfb5f5288d61586.1616506559.git.matti.vaittinen@fi.rohmeurope.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org Hi, On 3/23/21 2:56 PM, Matti Vaittinen wrote: > A few drivers which need a delayed work-queue must cancel work at driver > detach. Some of those implement remove() solely for this purpose. Help > drivers to avoid unnecessary remove and error-branch implementation by > adding managed verision of delayed work initialization. This will also > help drivers to avoid mixing manual and devm based unwinding when other > resources are handled by devm. > > Signed-off-by: Matti Vaittinen Thanks, patch looks good to me: Reviewed-by: Hans de Goede Regards, Hans > --- > Changelog from RFCv2: > - RFC dropped. No functional changes. > > include/linux/devm-helpers.h | 53 ++++++++++++++++++++++++++++++++++++ > 1 file changed, 53 insertions(+) > create mode 100644 include/linux/devm-helpers.h > > diff --git a/include/linux/devm-helpers.h b/include/linux/devm-helpers.h > new file mode 100644 > index 000000000000..f64e0c9f3763 > --- /dev/null > +++ b/include/linux/devm-helpers.h > @@ -0,0 +1,53 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > +#ifndef __LINUX_DEVM_HELPERS_H > +#define __LINUX_DEVM_HELPERS_H > + > +/* > + * Functions which do automatically cancel operations or release resources upon > + * driver detach. > + * > + * These should be helpful to avoid mixing the manual and devm-based resource > + * management which can be source of annoying, rarely occurring, > + * hard-to-reproduce bugs. > + * > + * Please take into account that devm based cancellation may be performed some > + * time after the remove() is ran. > + * > + * Thus mixing devm and manual resource management can easily cause problems > + * when unwinding operations with dependencies. IRQ scheduling a work in a queue > + * is typical example where IRQs are often devm-managed and WQs are manually > + * cleaned at remove(). If IRQs are not manually freed at remove() (and this is > + * often the case when we use devm for IRQs) we have a period of time after > + * remove() - and before devm managed IRQs are freed - where new IRQ may fire > + * and schedule a work item which won't be cancelled because remove() was > + * already ran. > + */ > + > +#include > +#include > + > +static inline void devm_delayed_work_drop(void *res) > +{ > + cancel_delayed_work_sync(res); > +} > + > +/** > + * devm_delayed_work_autocancel - Resource-managed work allocation > + * @dev: Device which lifetime work is bound to > + * @pdata: work to be cancelled when driver is detached > + * > + * Initialize work which is automatically cancelled when driver is detached. > + * A few drivers need delayed work which must be cancelled before driver > + * is detached to avoid accessing removed resources. > + * devm_delayed_work_autocancel() can be used to omit the explicit > + * cancelleation when driver is detached. > + */ > +static inline int devm_delayed_work_autocancel(struct device *dev, > + struct delayed_work *w, > + work_func_t worker) > +{ > + INIT_DELAYED_WORK(w, worker); > + return devm_add_action(dev, devm_delayed_work_drop, w); > +} > + > +#endif >