Re: [REGRESSION] 6.1.y/6.6.y: fsl-usb fails to build

[Ralf Lici <ralf@mandelbit.com>]

On Fri, 28 Aug 2026 07:44:44 +0200, Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> On Thu, Aug 27, 2026 at 05:43:00PM +0200, Ralf Lici wrote:
> > Hi,
> > 
> > While working on some backport patches for an out-of-tree module and
> > looking for the exact versions containing the disable_delayed_work_sync
> > symbol, I stumbled upon occurrences of that function on longterm v6.1
> > and v6.6 in drivers/usb/phy/phy-fsl-usb.c despite not being declared or
> > defined anywhere. In fact, disable_delayed_work_sync was introduced by
> > upstream commit 86898fa6b8cd ("workqueue: Implement disable/enable for
> > (delayed) work items") and is only available since v6.10. Neither 6.1.y
> > nor 6.6.y defines it.
> > 
> > Consequently, kernels built with CONFIG_FSL_USB2_OTG fail with:
> > 
> > drivers/usb/phy/phy-fsl-usb.c:990:2: error: call to undeclared function 'disable_delayed_work_sync'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> >   990 |         disable_delayed_work_sync(&fsl_otg_dev->otg_event);
> >       |         ^
> > drivers/usb/phy/phy-fsl-usb.c:990:2: note: did you mean 'cancel_delayed_work_sync'?
> > include/linux/workqueue.h:470:13: note: 'cancel_delayed_work_sync' declared here
> >   470 | extern bool cancel_delayed_work_sync(struct delayed_work *dwork);
> >       |             ^
> > 
> > I reproduced the failure on PowerPC using corenet64_smp_defconfig with
> > CONFIG_FSL_USB2_OTG=m, building drivers/usb/phy/phy-fsl-usb.o with
> > Clang.
> > 
> > AFAICT, in 6.1.y, the regression was introduced in v6.1.160 by commit
> > 4476c73bbbb0 ("usb: phy: fsl-usb: Fix use-after-free in delayed work
> > during device removal") and remains present in v6.1.185.
> > 
> > In 6.6.y, it was introduced in v6.6.120 by commit 319f7a85b3c4 ("usb:
> > phy: fsl-usb: Fix use-after-free in delayed work during device removal")
> > and remains present in v6.6.154.
> > 
> > Note that the same problem was pointed out by Ben Hutchings during the
> > 5.10.y review:
> > https://lore.kernel.org/all/d147f0eb71f9cefbfb7605e95d98564d7f0ed346.camel@decadent.org.uk/
> > 
> > The corresponding patches were dropped from 5.10.y and 5.15.y, but
> > appear to have been retained in 6.1.y and 6.6.y.
> > 
> > Simply replacing disable_delayed_work_sync with cancel_delayed_work_sync
> > at its current location may not be sufficient: it looks like the delayed
> > work can also be scheduled from fsl_otg_set_host and from the IRQ
> > handler but I'm not familiar with this part of the kernel.
>
> Can you just send patches to revert the offending commits?  Or we can
> just ignore it as it's been this way for a while and no one has noticed
> which implies to me that no one builds these modules for these arches on
> these very old kernel trees :)
>

Right, the lack of reports after roughly ten months suggests that nobody
is building these modules for the affected configurations. Still, I
would rather not knowingly leave those configurations unbuildable, so
I'll send revert patches shortly.

Thanks,

-- 
Ralf Lici
Mandelbit Srl