From: Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Andrew Lunn <andrew@lunn.ch>,
linux-can@vger.kernel.org, Marc Kleine-Budde <mkl@pengutronix.de>,
linux-kernel@vger.kernel.org,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
netdev@vger.kernel.org, linux-usb@vger.kernel.org,
Saeed Mahameed <saeed@kernel.org>, Jiri Pirko <jiri@nvidia.com>,
Lukas Magel <lukas.magel@posteo.net>
Subject: Re: [PATCH v4 2/6] can: etas_es58x: add devlink support
Date: Mon, 28 Nov 2022 14:32:23 +0900 [thread overview]
Message-ID: <CAMZ6RqKS0sUFZWQfmRU6q2ivWEUFD06uiQekDr=u94L3uij3yQ@mail.gmail.com> (raw)
In-Reply-To: <CAMZ6Rq+Gi+rcLqSj2-kug7c1G_nNuj6peh5nH1DNoo8B3aSxzw@mail.gmail.com>
On Mon. 28 Nov. 2022 at 10:34, Vincent MAILHOL
<mailhol.vincent@wanadoo.fr> wrote:
> On Mon. 28 Nov. 2022 at 00:41, Alan Stern <stern@rowland.harvard.edu> wrote:
> > On Sun, Nov 27, 2022 at 02:10:32PM +0900, Vincent MAILHOL wrote:
> > > > Should devlink_free() be after usb_set_inftdata()?
> > >
> > > A look at
> > > $ git grep -W "usb_set_intfdata(.*NULL)"
> > >
> > > shows that the two patterns (freeing before or after
> > > usb_set_intfdata()) coexist.
> > >
> > > You are raising an important question here. usb_set_intfdata() does
> > > not have documentation that freeing before it is risky. And the
> > > documentation of usb_driver::disconnect says that:
> > > "@disconnect: Called when the interface is no longer accessible,
> > > usually because its device has been (or is being) disconnected
> > > or the driver module is being unloaded."
> > > Ref: https://elixir.bootlin.com/linux/v6.1-rc6/source/include/linux/usb.h#L1130
> > >
> > > So the interface no longer being accessible makes me assume that the
> > > order does not matter. If it indeed matters, then this is a foot gun
> > > and there is some clean-up work waiting for us on many drivers.
> > >
> > > @Greg, any thoughts on whether or not the order of usb_set_intfdata()
> > > and resource freeing matters or not?
> >
> > In fact, drivers don't have to call usb_set_intfdata(NULL) at all; the
> > USB core does it for them after the ->disconnect() callback returns.
>
> Interesting. This fact is widely unknown, cf:
> $ git grep "usb_set_intfdata(.*NULL)" | wc -l
> 215
>
> I will do some clean-up later on, at least for the CAN USB drivers.
>
> > But if a driver does make the call, it should be careful to ensure that
> > the call happens _after_ the driver is finished using the interface-data
> > pointer. For example, after all outstanding URBs have completed, if the
> > completion handlers will need to call usb_get_intfdata().
>
> ACK. I understand that it should be called *after* the completion of
> any ongoing task.
>
> My question was more on:
>
> devlink_free(priv_to_devlink(es58x_dev));
> usb_set_intfdata(intf, NULL);
>
> VS.
>
> usb_set_intfdata(intf, NULL);
> devlink_free(priv_to_devlink(es58x_dev));
>
> From your comments, I understand that both are fine.
Do we agree that the usb-skeleton is doing it wrong?
https://elixir.bootlin.com/linux/latest/source/drivers/usb/usb-skeleton.c#L567
usb_set_intfdata(interface, NULL) is called before deregistering the
interface and terminating the outstanding URBs!
> > Remember, the interface-data pointer is owned by the driver. Nothing
> > else in the kernel uses it. So the driver merely has to be careful not
> > to clear the pointer while it is still using it.
>
> Thanks for your comments!
>
>
> Yours sincerely,
> Vincent Mailhol
next prev parent reply other threads:[~2022-11-28 5:32 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-04 7:36 [PATCH] can: etas_es58x: report the firmware version through ethtool Vincent Mailhol
2022-11-04 11:52 ` Marc Kleine-Budde
2022-11-04 15:35 ` Vincent MAILHOL
2022-11-04 17:16 ` [PATCH v2 0/3] can: etas_es58x: report firmware version Vincent Mailhol
2022-11-04 17:16 ` [PATCH v2 1/3] USB: core: export usb_cache_string() Vincent Mailhol
2022-11-05 8:22 ` Greg Kroah-Hartman
2022-11-04 17:16 ` [PATCH v2 2/3] can: etas_es58x: use usb_cache_string() to retrieve the product info string Vincent Mailhol
2022-11-05 8:21 ` Greg Kroah-Hartman
2022-11-04 17:16 ` [PATCH v2 3/3] can: etas_es58x: report the firmware version through ethtool Vincent Mailhol
2022-11-05 8:23 ` Greg Kroah-Hartman
2022-11-05 9:27 ` Vincent MAILHOL
2022-11-05 17:21 ` Vincent MAILHOL
2022-11-05 17:38 ` Greg Kroah-Hartman
2022-11-06 0:45 ` Alan Stern
2022-11-06 5:34 ` Vincent MAILHOL
2022-11-06 11:21 ` Greg Kroah-Hartman
2022-11-06 12:47 ` Vincent MAILHOL
2022-11-06 14:22 ` Greg Kroah-Hartman
2022-11-06 14:44 ` Vincent MAILHOL
2022-11-06 16:02 ` Greg Kroah-Hartman
2022-11-12 15:40 ` Vincent MAILHOL
2022-11-06 15:18 ` Alan Stern
2022-11-13 4:01 ` [PATCH v3 0/3] can: etas_es58x: report firmware, bootloader and hardware version Vincent Mailhol
2022-11-13 4:01 ` [PATCH v3 1/3] USB: core: export usb_cache_string() Vincent Mailhol
2022-11-22 16:00 ` Greg Kroah-Hartman
2022-11-13 4:01 ` [PATCH v3 2/3] can: etas_es58x: export firmware, bootloader and hardware versions in sysfs Vincent Mailhol
2022-11-15 22:47 ` Saeed Mahameed
2022-11-16 0:36 ` Vincent MAILHOL
2022-11-16 23:20 ` Saeed Mahameed
2022-11-13 4:01 ` [PATCH v3 3/3] can: etas_es58x: report firmware-version through ethtool Vincent Mailhol
2022-11-13 16:48 ` [PATCH v3 0/3] can: etas_es58x: report firmware, bootloader and hardware version Andrew Lunn
2022-11-14 16:49 ` Vincent MAILHOL
2022-11-14 17:08 ` Andrew Lunn
2022-11-26 16:22 ` [PATCH v4 0/6] " Vincent Mailhol
2022-11-26 16:22 ` [PATCH v4 1/6] USB: core: export usb_cache_string() Vincent Mailhol
2022-11-26 16:22 ` [PATCH v4 2/6] can: etas_es58x: add devlink support Vincent Mailhol
2022-11-26 16:51 ` Andrew Lunn
2022-11-27 5:10 ` Vincent MAILHOL
2022-11-27 15:36 ` Alan Stern
2022-11-28 1:34 ` Vincent MAILHOL
2022-11-28 5:32 ` Vincent MAILHOL [this message]
2022-11-28 15:50 ` Alan Stern
2022-11-28 23:30 ` Vincent MAILHOL
2022-11-28 13:42 ` Andrew Lunn
2022-11-28 14:29 ` Vincent MAILHOL
2022-11-26 16:22 ` [PATCH v4 3/6] can: etas_es58x: export product information through devlink_ops::info_get() Vincent Mailhol
2022-11-26 17:16 ` Andrew Lunn
2022-11-27 3:42 ` Vincent MAILHOL
2022-11-27 4:31 ` Vincent MAILHOL
2022-11-27 15:07 ` Andrew Lunn
2022-11-28 1:21 ` Vincent MAILHOL
2022-11-28 13:43 ` Andrew Lunn
2022-11-28 13:47 ` Andrew Lunn
2022-11-28 14:43 ` Vincent MAILHOL
2022-11-28 22:27 ` Jakub Kicinski
2022-11-28 23:17 ` Vincent MAILHOL
2022-11-26 16:22 ` [PATCH v4 4/6] can: etas_es58x: remove es58x_get_product_info() Vincent Mailhol
2022-11-28 13:44 ` Andrew Lunn
2022-11-28 14:36 ` Vincent MAILHOL
2022-11-26 16:22 ` [PATCH v4 5/6] can: etas_es58x: report the firmware version through ethtool Vincent Mailhol
2022-11-28 13:44 ` Andrew Lunn
2022-11-28 22:29 ` Jakub Kicinski
2022-11-29 17:12 ` Vincent MAILHOL
2022-11-30 2:31 ` Jakub Kicinski
2022-11-26 16:22 ` [PATCH v4 6/6] Documentation: devlink: add devlink documentation for the etas_es58x driver Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 0/7] can: etas_es58x: report firmware, bootloader and hardware version Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 1/7] can: etas_es58x: add devlink support Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 2/7] can: etas_es58x: add devlink port support Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 3/7] USB: core: export usb_cache_string() Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 4/7] net: devlink: add DEVLINK_INFO_VERSION_GENERIC_FW_BOOTLOADER Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 5/7] can: etas_es58x: export product information through devlink_ops::info_get() Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 6/7] can: etas_es58x: remove es58x_get_product_info() Vincent Mailhol
2022-11-30 17:46 ` [PATCH v5 7/7] Documentation: devlink: add devlink documentation for the etas_es58x driver Vincent Mailhol
2022-12-02 12:27 ` Marc Kleine-Budde
2022-12-02 13:15 ` Vincent MAILHOL
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