linux-kernel - Re: [PATCH] refcount_t: add ACQUIRE ordering on success for dec(sub)_and

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Message-ID: <20190129095144.GH28467@hirez.programming.kicks-ass.net>
Date:   Tue, 29 Jan 2019 10:51:44 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Andrea Parri <andrea.parri@...rulasolutions.com>
Cc:     Elena Reshetova <elena.reshetova@...el.com>,
        linux-kernel@...r.kernel.org, keescook@...omium.org,
        Alan Stern <stern@...land.harvard.edu>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] refcount_t: add ACQUIRE ordering on success for
 dec(sub)_and_test variants

On Mon, Jan 28, 2019 at 03:29:10PM +0100, Andrea Parri wrote:

> > diff --git a/arch/x86/include/asm/refcount.h b/arch/x86/include/asm/refcount.h
> > index dbaed55..ab8f584 100644
> > --- a/arch/x86/include/asm/refcount.h
> > +++ b/arch/x86/include/asm/refcount.h
> > @@ -67,16 +67,29 @@ static __always_inline void refcount_dec(refcount_t *r)
> >  static __always_inline __must_check
> >  bool refcount_sub_and_test(unsigned int i, refcount_t *r)
> >  {
> > -	return GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl",
> > +	bool ret = GEN_BINARY_SUFFIXED_RMWcc(LOCK_PREFIX "subl",
> >  					 REFCOUNT_CHECK_LT_ZERO,
> >  					 r->refs.counter, e, "er", i, "cx");
> > +
> > +    if (ret) {
> > +               smp_acquire__after_ctrl_dep();
> > +               return true;
> > +    }
> > +
> > +    return false;
> 
> There appears to be some white-space damage (here and in other places);
> checkpatch.pl should point these and other style problems out.

It's worse...

patch: **** malformed patch at line 81: diff --git a/arch/x86/include/asm/refcount.h b/arch/x86/include/asm/refcount.h

And yes, there's a lot of whitespace damage all around. Lots of trailing
spaces too.