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SubjectRe: [PATCH v4] uart: fix race between uart_put_char() and uart_shutdown()
On Thu, Jul 12, 2018 at 12:30:01PM -0600, Tycho Andersen wrote:
> On Thu, Jul 12, 2018 at 08:25:45PM +0200, Greg Kroah-Hartman wrote:
> > On Thu, Jul 12, 2018 at 12:18:46PM -0600, Tycho Andersen wrote:
> > > On Thu, Jul 12, 2018 at 05:40:15PM +0200, Greg Kroah-Hartman wrote:
> > > > On Thu, Jul 12, 2018 at 09:08:22AM -0600, Tycho Andersen wrote:
> > > > > On Thu, Jul 12, 2018 at 05:04:38PM +0200, Greg Kroah-Hartman wrote:
> > > > > > On Wed, Jul 11, 2018 at 10:07:44AM -0600, Tycho Andersen wrote:
> > > > > > > + if (uport)
> > > > > > > + spin_lock_irqsave(&uport->lock, flags);
> > > > > >
> > > > > > That's the same thing as just calling uart_port_lock(), why aren't you
> > > > > > doing that?
> > > > >
> > > > > Because the compiler can't seem to "see" through the macros/ref calls,
> > > > > and I get the warning I mentioned here if I use them:
> > > > >
> > > > > https://lkml.org/lkml/2018/7/6/840
> > > >
> > > > What horrible version of gcc are you using that give you that? Don't
> > > > open-code things just because of a broken compiler.
> > >
> > > I've tried with both 7.3.0 and 5.4.0. I think the reason we see this
> > > here but not elsewhere in the file is because there's an actual
> > > function call (free_page()) in the critical section.
> > >
> > > If we move that out, something like the below patch, it all works for
> > > me.
> >
> > Ick. Which version of this series had the problem? Let me test it out
> > here...
>
> v3, if you remove the initialization of flags from both functions you
> should see it.

Ok, I tried v3 out and yes, you are right, removing the "= 0" causes gcc
to complain. The compiler is being dumb here, so I'll just leave it
as-is. I've queued up the v3 version now, thanks for sticking with
this.

greg k-h
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