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

[Ralf Lici <ralf@mandelbit.com>]

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.

Cheers!

-- 
Ralf Lici
Mandelbit Srl