linux-kernel - Re: [PATCH -rcu/kcsan 05/23] kcsan: Add core memory barrier instrumentation functions

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Message-ID: <CANpmjNOXWtUg9qsLJ6m9n3GYZf-AHE_21=zLnFnUMDBHMP2umg@mail.gmail.com>
Date:   Tue, 5 Oct 2021 13:50:41 +0200
From:   Marco Elver <elver@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     "Paul E . McKenney" <paulmck@...nel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Ingo Molnar <mingo@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Waiman Long <longman@...hat.com>,
        Will Deacon <will@...nel.org>, kasan-dev@...glegroups.com,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH -rcu/kcsan 05/23] kcsan: Add core memory barrier
 instrumentation functions

On Tue, 5 Oct 2021 at 13:45, Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, Oct 05, 2021 at 01:41:18PM +0200, Peter Zijlstra wrote:
> > On Tue, Oct 05, 2021 at 12:58:47PM +0200, Marco Elver wrote:
> > > +static __always_inline void kcsan_atomic_release(int memorder)
> > > +{
> > > +   if (memorder == __ATOMIC_RELEASE ||
> > > +       memorder == __ATOMIC_SEQ_CST ||
> > > +       memorder == __ATOMIC_ACQ_REL)
> > > +           __kcsan_release();
> > > +}
> > > +
[...]
> > > +   kcsan_atomic_release(memorder);
> > >     __atomic_thread_fence(memorder);
> > >  }
> > >  EXPORT_SYMBOL(__tsan_atomic_thread_fence);
> >
> > I find that very hard to read.. kcsan_atomic_release() it not in fact a
> > release. It might be a release if @memorder implies one.

You're right, this name can be improved.
`kcsan_atomic_builtin_memorder(..)` is probably better

> Also, what's the atomic part signify? Is that because you're modeling
> the difference in acquire/release semantics between
> smp_load_{acquire,release}() and atomic*_{acquire,release}() ?

Sorry, just a bad name. It's about the builtins. The above suggested
name should hopefully be clearer.