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From: hev <r@hev.cc>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
	Rui Wang <wangrui@loongson.cn>, Ingo Molnar <mingo@redhat.com>,
	Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>, Guo Ren <guoren@kernel.org>,
	linux-arch <linux-arch@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Xuefeng Li <lixuefeng@loongson.cn>,
	Huacai Chen <chenhuacai@gmail.com>,
	Jiaxun Yang <jiaxun.yang@flygoat.com>,
	Huacai Chen <chenhuacai@loongson.cn>,
	kernel test robot <lkp@intel.com>
Subject: Re: [RFC PATCH v3] locking/atomic: Implement atomic{,64,_long}_{fetch_,}{andnot_or}{,_relaxed,_acquire,_release}()
Date: Fri, 30 Jul 2021 10:50:53 +0800	[thread overview]
Message-ID: <CAHirt9iYhmQPjMNn_RxBib8fumR0RhjVoBN1ggGm-9MSMHu4Rw@mail.gmail.com> (raw)
In-Reply-To: <20210729123522.GB21766@willie-the-truck>

Hi,

On Thu, Jul 29, 2021 at 8:35 PM Will Deacon <will@kernel.org> wrote:
>
> On Thu, Jul 29, 2021 at 01:43:41PM +0200, Arnd Bergmann wrote:
> > On Thu, Jul 29, 2021 at 11:56 AM Will Deacon <will@kernel.org> wrote:
> > > On Thu, Jul 29, 2021 at 05:30:03PM +0800, Rui Wang wrote:
> > > > This patch introduce a new atomic primitive andnot_or:
> > >
> > > Please see my other comments on the other patches you posted:
> > >
> > > https://lore.kernel.org/r/20210729093923.GD21151@willie-the-truck
> > >
> > > Overall, I'm not thrilled to bits by extending the atomics API with
> > > operations that cannot be implemented efficiently on any (?) architectures
> > > and are only used by the qspinlock slowpath on machines with more than 16K
> > > CPUs.
> >
> > Wouldn't this also help improve set_mask_bits()? That one at least has
> > a handful of users in the kernel.
>
> For pure LL/SC architectures, yes, but I don't think it helps anybody else.
>
> Afaict, an architecture can already override set_mask_bits, so why do we
> need to add this primitive to the atomic API?
>
> Will

So what's next?

Now the set_mask_bits return oldval, return newval before 5.0. :-D
commit 1db604f676b("include/linux/bitops.h: set_mask_bits() to return
old value")

Regards,
Rui

      reply	other threads:[~2021-07-30  2:51 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29  9:30 [RFC PATCH v3] locking/atomic: Implement atomic{,64,_long}_{fetch_,}{andnot_or}{,_relaxed,_acquire,_release}() Rui Wang
2021-07-29  9:55 ` Will Deacon
2021-07-29 10:58   ` hev
2021-07-29 11:15   ` Peter Zijlstra
2021-07-29 12:34     ` Will Deacon
2021-07-29 11:43   ` Arnd Bergmann
2021-07-29 12:35     ` Will Deacon
2021-07-30  2:50       ` hev [this message]

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