linux-kernel - Re: [RFC 1/2] refcount: introduce generic lockptr funcs

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Message-ID: <CAK-6q+hQnTgmO_2qfNDzyYW36T1aH+a5q285G+Rfo+sN4dfEfA@mail.gmail.com>
Date:   Fri, 3 Nov 2023 15:20:08 -0400
From:   Alexander Aring <aahringo@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     will@...nel.org, gfs2@...ts.linux.dev, boqun.feng@...il.com,
        mark.rutland@....com, linux-kernel@...r.kernel.org
Subject: Re: [RFC 1/2] refcount: introduce generic lockptr funcs

Hi,

On Fri, Nov 3, 2023 at 2:54 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Fri, Nov 03, 2023 at 12:16:34PM -0400, Alexander Aring wrote:
>
> > diff --git a/lib/refcount.c b/lib/refcount.c
> > index a207a8f22b3c..e28678f0f473 100644
> > --- a/lib/refcount.c
> > +++ b/lib/refcount.c
> > @@ -94,6 +94,34 @@ bool refcount_dec_not_one(refcount_t *r)
> >  }
> >  EXPORT_SYMBOL(refcount_dec_not_one);
> >
> > +bool refcount_dec_and_lockptr(refcount_t *r, void (*lock)(void *lockptr),
> > +                           void (*unlock)(void *lockptr),  void *lockptr)
> > +{
> > +     if (refcount_dec_not_one(r))
> > +             return false;
> > +
> > +     lock(lockptr);
> > +     if (!refcount_dec_and_test(r)) {
> > +             unlock(lockptr);
> > +             return false;
> > +     }
> > +
> > +     return true;
> > +}
> > +EXPORT_SYMBOL(refcount_dec_and_lockptr);
>
> This is terrible, you're forcing indirect calls on everything.
>

Okay, I see. How about introducing a macro producing all the code at
preprocessor time?

- Alex