linux-kernel - Re: [PATCH V8 10/10] csky: Add qspinlock support

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Date:   Mon, 25 Jul 2022 10:30:33 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Palmer Dabbelt <palmer@...osinc.com>,
        Heiko Stübner <heiko@...ech.de>,
        Christoph Hellwig <hch@...radead.org>,
        Arnd Bergmann <arnd@...db.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Ingo Molnar <mingo@...hat.com>,
        Philipp Tomsich <philipp.tomsich@...ll.eu>,
        Christoph Muellner <cmuellner@...ux.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        David Laight <David.Laight@...lab.com>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-csky@...r.kernel.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V8 10/10] csky: Add qspinlock support

On Mon, Jul 25, 2022 at 10:08 AM Waiman Long <longman@...hat.com> wrote:
>
> On 7/24/22 08:25, guoren@...nel.org wrote:
> > From: Guo Ren <guoren@...ux.alibaba.com>
> >
> > Enable qspinlock by the requirements mentioned in a8ad07e5240c9
> > ("asm-generic: qspinlock: Indicate the use of mixed-size atomics").
> >
> > C-SKY only has "ldex/stex" for all atomic operations. So csky give a
> > strong forward guarantee for "ldex/stex." That means when ldex grabbed
> > the cache line into $L1, it would block other cores from snooping the
> > address with several cycles.
> >
> > Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@...nel.org>
> > ---
> >   arch/csky/Kconfig               | 16 ++++++++++++++++
> >   arch/csky/include/asm/Kbuild    |  2 ++
> >   arch/csky/include/asm/cmpxchg.h | 20 ++++++++++++++++++++
> >   3 files changed, 38 insertions(+)
> >
> > diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
> > index dfdb436b6078..09f7d1f06bca 100644
> > --- a/arch/csky/Kconfig
> > +++ b/arch/csky/Kconfig
> > @@ -354,6 +354,22 @@ config HAVE_EFFICIENT_UNALIGNED_STRING_OPS
> >         Say Y here to enable EFFICIENT_UNALIGNED_STRING_OPS. Some CPU models could
> >         deal with unaligned access by hardware.
> >
> > +choice
> > +     prompt "C-SKY spinlock type"
> > +     default CSKY_TICKET_SPINLOCKS
> > +
> > +config CSKY_TICKET_SPINLOCKS
> > +     bool "Using ticket spinlock"
> > +
> > +config CSKY_QUEUED_SPINLOCKS
> > +     bool "Using queued spinlock"
> > +     depends on SMP
> > +     select ARCH_USE_QUEUED_SPINLOCKS
> > +     help
> > +       Make sure your micro arch LL/SC has a strong forward progress guarantee.
> > +       Otherwise, stay at ticket-lock/combo-lock.
>
> "combo-lock"? It is a cut-and-paste error. Right?
Yes, it's a typo. No combo-lock for csky.

>
> Cheers,
> Longman
>


-- 
Best Regards
 Guo Ren