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[73.241.114.122]) by smtp.gmail.com with ESMTPSA id u18sm38877903pgn.9.2019.12.27.07.02.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 27 Dec 2019 07:02:21 -0800 (PST) Date: Fri, 27 Dec 2019 07:02:19 -0800 From: Richard Cochran To: Vladis Dronov Cc: linux-fsdevel@vger.kernel.org, Alexander Viro , Al Viro , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] ptp: fix the race between the release of ptp_clock and cdev Message-ID: <20191227150218.GA1435@localhost> References: <20191208195340.GX4203@ZenIV.linux.org.uk> <20191227022627.24476-1-vdronov@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191227022627.24476-1-vdronov@redhat.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Dec 27, 2019 at 03:26:27AM +0100, Vladis Dronov wrote: > Here cdev is embedded in posix_clock which is embedded in ptp_clock. > The race happens because ptp_clock's lifetime is controlled by two > refcounts: kref and cdev.kobj in posix_clock. This is wrong. > > Make ptp_clock's sysfs device a parent of cdev with cdev_device_add() > created especially for such cases. This way the parent device with its > ptp_clock is not released until all references to the cdev are released. > This adds a requirement that an initialized but not exposed struct > device should be provided to posix_clock_register() by a caller instead > of a simple dev_t. > > This approach was adopted from the commit 72139dfa2464 ("watchdog: Fix > the race between the release of watchdog_core_data and cdev"). See > details of the implementation in the commit 233ed09d7fda ("chardev: add > helper function to register char devs with a struct device"). Thanks for digging into this! Acked-by: Richard Cochran > /** > * posix_clock_register() - register a new clock > - * @clk: Pointer to the clock. Caller must provide 'ops' and 'release' > - * @devid: Allocated device id > + * @clk: Pointer to the clock. Caller must provide 'ops' field > + * @dev: Pointer to the initialized device. Caller must provide > + * 'release' filed field Thanks, Richard