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Date: Fri, 27 Dec 2019 12:24:13 -0500 (EST) From: Vladis Dronov <vdronov@...hat.com> To: Richard Cochran <richardcochran@...il.com> Cc: linux-fsdevel@...r.kernel.org, Alexander Viro <viro@...iv.linux.org.uk>, Al Viro <aviro@...hat.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2] ptp: fix the race between the release of ptp_clock and cdev Hello, Richard, Thank you for the review! > > + * @dev: Pointer to the initialized device. Caller must provide > > + * 'release' filed > > field Indeed. *sigh* Nothing is ideal. Let's hope a maintainer could fix it if this is approved. Best regards, Vladis Dronov | Red Hat, Inc. | The Core Kernel | Senior Software Engineer ----- Original Message ----- > From: "Richard Cochran" <richardcochran@...il.com> > To: "Vladis Dronov" <vdronov@...hat.com> > Cc: linux-fsdevel@...r.kernel.org, "Alexander Viro" <viro@...iv.linux.org.uk>, "Al Viro" <aviro@...hat.com>, > netdev@...r.kernel.org, linux-kernel@...r.kernel.org > Sent: Friday, December 27, 2019 4:02:19 PM > Subject: Re: [PATCH v2] ptp: fix the race between the release of ptp_clock and cdev > > 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 <richardcochran@...il.com> > > > /** > > * 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
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