Re: [PATCH] usb: gadget: udc: max3420_udc: fix serialized access

[Jassi Brar]

On Wed, 8 Feb 2023 at 11:23, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Feb 08, 2023 at 10:34:18AM -0600, jassisinghbrar@xxxxxxxxx wrote:
> > From: Jassi Brar <jaswinder.singh@xxxxxxxxxx>
> >
> >  The mutex 'spi_bus_mutex' should be used, instead of the spin-lock,
> > while changing the state of the kernel-thread.
>
> You forgot to say why this is the case.
>
It was 'inherited' (my fault) from  drivers/usb/host/max3421-hcd.c
which has the same issue.
OK, I will also add to the log why that is a bad idea.

> > Also changing the
> > usb-gadget state need not be protected by a spin-lock.
>
> Why not?  Why isn't this a separate change?
>
Because other low-level spi changes are protected by spin-lock and it
seems ok to not to have to worry about such a race.
I don't have the h/w anymore to actually test it, so it is just a
patch from looking.
I just got lazy to break it into two patches, will do that.

> >  This should fix the Smatch static checker warning
> >     warn: sleeping in atomic context
> >
> > Fixes: 48ba02b2e2b1 ("usb: gadget: add udc driver for max3420")
> > Signed-off-by: Jassi Brar <jaswinder.singh@xxxxxxxxxx>
> > ---
> >  drivers/usb/gadget/udc/max3420_udc.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
>
> You forgot a "Reported-by:" line, right?
>
Yes, I forgot.

thanks.