linux-kernel - Re: [RFC PATCH] locking/atomic: arch/mips: Fix atomic{_64,}_sub_if

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Message-ID: <CAHirt9igj7wzrNKWUaoEnofWEwF1VtjuBpvgRGZpMiGphJmPCQ@mail.gmail.com>
Date:   Wed, 4 Aug 2021 21:46:50 +0800
From:   hev <r@....cc>
To:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>
Cc:     Rui Wang <wangrui@...ngson.cn>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-mips@...r.kernel.org
Subject: Re: [RFC PATCH] locking/atomic: arch/mips: Fix atomic{_64,}_sub_if_positive

On Thu, Jul 29, 2021 at 10:33 PM Thomas Bogendoerfer
<tsbogend@...ha.franken.de> wrote:
>
> On Thu, Jul 29, 2021 at 08:31:11PM +0800, hev wrote:
> > Hi, Thomas,
> >
> > On Thu, Jul 29, 2021 at 5:53 PM Thomas Bogendoerfer
> > <tsbogend@...ha.franken.de> wrote:
> > >
> > > On Thu, Jul 29, 2021 at 04:25:49PM +0800, Rui Wang wrote:
> > > > This looks like a typo and that caused atomic64 test failed.
> > > >
> > > > Signed-off-by: Rui Wang <wangrui@...ngson.cn>
> > > > Signed-off-by: hev <r@....cc>
> > > > ---
> > > >  arch/mips/include/asm/atomic.h | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/arch/mips/include/asm/atomic.h b/arch/mips/include/asm/atomic.h
> > > > index 95e1f7f3597f..a0b9e7c1e4fc 100644
> > > > --- a/arch/mips/include/asm/atomic.h
> > > > +++ b/arch/mips/include/asm/atomic.h
> > > > @@ -206,7 +206,7 @@ ATOMIC_OPS(atomic64, xor, s64, ^=, xor, lld, scd)
> > > >   * The function returns the old value of @v minus @i.
> > > >   */
> > > >  #define ATOMIC_SIP_OP(pfx, type, op, ll, sc)                         \
> > > > -static __inline__ int arch_##pfx##_sub_if_positive(type i, pfx##_t * v)      \
> > > > +static __inline__ type arch_##pfx##_sub_if_positive(type i, pfx##_t * v)     \
> > > >  {                                                                    \
> > > >       type temp, result;                                              \
> > > >                                                                       \
> > >
> > > sub_if_postive looks unused to me. Could you send a patch removing it
> > > instead ? riscv also has a sub_if_positive implementation, which looks
> > > unused.
> > I found atomic{_64,}_dec_if_postive is based on sub_if_postive, and
> > used in many places:
> >
> > kernel/kmod.c:    if (atomic_dec_if_positive(&kmod_concurrent_max) < 0) {
> > kernel/kmod.c:
> > atomic_dec_if_positive(&kmod_concurrent_max) >= 0,
> > kernel/module.c:        ret = atomic_dec_if_positive(&module->refcnt);
> > ...
> > drivers/net/ethernet/mellanox/mlx5/core/eswitch.c:
> > atomic64_dec_if_positive(&esw->user_count);
> > drivers/net/netdevsim/fib.c:        atomic64_dec_if_positive(&entry->num);
> > drivers/net/netdevsim/fib.c:        atomic64_dec_if_positive(&entry->num);
> >
> > Are you sure to remove it?
>
> in that case, let's keep it. There is a fallback for atomic_dec_if_positive,
> that's why I didn't notice where it is used.

yep, do you think this patch is okay?

Regards,

Rui