linux-kernel - Re: [PATCH 1/2] vmw_vmci: Clean up uses of atomic*

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Message-ID: <20190524115612.GA21365@andrea>
Date:   Fri, 24 May 2019 13:56:12 +0200
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jorgen Hansen <jhansen@...are.com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>
Subject: Re: [PATCH 1/2] vmw_vmci: Clean up uses of atomic*_set()

On Fri, May 24, 2019 at 12:39:34PM +0200, Peter Zijlstra wrote:
> On Fri, May 24, 2019 at 12:35:35PM +0200, Andrea Parri wrote:
> > The primitive vmci_q_set_pointer() relies on atomic*_set() being of
> > type 'void', but this is a non-portable implementation detail.
> > 
> > Reported-by: Mark Rutland <mark.rutland@....com>
> > Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
> > Cc: Arnd Bergmann <arnd@...db.de>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Jorgen Hansen <jhansen@...are.com>
> > Cc: Peter Zijlstra <peterz@...radead.org>
> > Cc: Will Deacon <will.deacon@....com>
> > Cc: Mark Rutland <mark.rutland@....com>
> > Cc: "Paul E. McKenney" <paulmck@...ux.ibm.com>
> > ---
> >  include/linux/vmw_vmci_defs.h | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/linux/vmw_vmci_defs.h b/include/linux/vmw_vmci_defs.h
> > index 0c06178e4985b..eb593868e2e9e 100644
> > --- a/include/linux/vmw_vmci_defs.h
> > +++ b/include/linux/vmw_vmci_defs.h
> > @@ -759,9 +759,9 @@ static inline void vmci_q_set_pointer(atomic64_t *var,
> >  				      u64 new_val)
> >  {
> >  #if defined(CONFIG_X86_32)
> > -	return atomic_set((atomic_t *)var, (u32)new_val);
> > +	atomic_set((atomic_t *)var, (u32)new_val);
> >  #else
> > -	return atomic64_set(var, new_val);
> > +	atomic64_set(var, new_val);
> >  #endif
> >  }
> 
> All that should just die a horrible death. That code is crap.
> 
> See:
> 
>   lkml.kernel.org/r/20190524103731.GN2606@...ez.programming.kicks-ass.net

I see, that was indeed 'racy' with my patch!  ;-)  Thank you!

  Andrea