Re: [PATCH v3] uart: fix race between uart_put_char() and uart_shutdown()

From: Tycho Andersen
Date: Fri Jul 06 2018 - 17:22:35 EST


On Fri, Jul 06, 2018 at 11:48:58PM +0300, Andy Shevchenko wrote:
> On Fri, Jul 6, 2018 at 9:39 PM, Tycho Andersen <tycho@xxxxxxxx> wrote:
> > On Fri, Jul 06, 2018 at 07:49:09PM +0300, Andy Shevchenko wrote:
> >> On Fri, Jul 6, 2018 at 7:24 PM, Tycho Andersen <tycho@xxxxxxxx> wrote:
>
> > but without the initialization I get,
> >
> > CC drivers/tty/serial/serial_core.o
> > In file included from ./include/linux/seqlock.h:36:0,
> > from ./include/linux/time.h:6,
> > from ./include/linux/stat.h:19,
> > from ./include/linux/module.h:10,
> > from drivers/tty/serial/serial_core.c:10:
> > drivers/tty/serial/serial_core.c: In function âuart_startup.part.20â:
> > ./include/linux/spinlock.h:260:3: warning: âflagsâ may be used uninitialized in this function -Wmaybe-uninitialized]
> > _raw_spin_unlock_irqrestore(lock, flags); \
> > ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> > drivers/tty/serial/serial_core.c:184:22: note: âflagsâ was declared here
> > unsigned long page, flags;
> > ^~~~~
>
> Hmm... I didn't see such warning. How you run make?

Just with `make`, although using the specific object file works too.
Perhaps it's gcc versions?

~/packages/linux uart-fix-v4 make drivers/tty/serial/serial_core.o
CALL scripts/checksyscalls.sh
DESCEND objtool
CC drivers/tty/serial/serial_core.o
In file included from ./include/linux/seqlock.h:36:0,
from ./include/linux/time.h:6,
from ./include/linux/stat.h:19,
from ./include/linux/module.h:10,
from drivers/tty/serial/serial_core.c:10:
drivers/tty/serial/serial_core.c: In function âuart_startup.part.20â:
./include/linux/spinlock.h:260:3: warning: âflagsâ may be used uninitialized in this function -Wmaybe-uninitialized]
_raw_spin_unlock_irqrestore(lock, flags); \
^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/tty/serial/serial_core.c:184:22: note: âflagsâ was declared here
unsigned long page, flags;
^~~~~
In file included from ./include/linux/seqlock.h:36:0,
from ./include/linux/time.h:6,
from ./include/linux/stat.h:19,
from ./include/linux/module.h:10,
from drivers/tty/serial/serial_core.c:10:
drivers/tty/serial/serial_core.c: In function âuart_shutdownâ:
./include/linux/spinlock.h:260:3: warning: âflagsâ may be used uninitialized in this function -Wmaybe-uninitialized]
_raw_spin_unlock_irqrestore(lock, flags); \
^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/tty/serial/serial_core.c:269:16: note: âflagsâ was declared here
unsigned long flags;
^~~~~
~/packages/linux uart-fix-v4 gcc --version
gcc (Ubuntu 7.3.0-16ubuntu3) 7.3.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

> Btw, you adding the only places with such assignments in this file.
> So, I would not do in your case, until entire file would be fixed.
>
> (But warning looks bogus, or you have some patches on top of current
> vanilla / next)

I don't have any patches, but I do admit to not thinking about it very hard and
adding initializations. I'll see if I can figure out what's going on.

Thanks,

Tycho