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

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Date:   Tue, 29 Jan 2019 13:39:17 +0000
From:   "Reshetova, Elena" <elena.reshetova@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Andrea Parri <andrea.parri@...rulasolutions.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "keescook@...omium.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.


I am very sorry about this, smth is really wrong with my system, in addition to all
above, I haven't even received Andrea reply to my inbox, neither this patch itself. 

I will fix all the whitespacing/trailing stuff and address this comment from Andrea:

"Mmh, this property (A-cumulativity) isn't really associated to ACQUIREs
in the LKMM; I'd suggest to simply remove the last sentence."

Anything else that needs fixing, content-wise? 

Best Regards,
Elena.