linux-kernel - Re: [PATCH v4 2/3] locking/rwsem: Remove rwsem-spinlock.c & use rwsem-xadd.c for all archs

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Message-ID: <CAMuHMdVe9J4LmbLz8nHsW2JSVt8EQHTKswtc+-53pD-DBxgwSw@mail.gmail.com>
Date:   Thu, 14 Feb 2019 11:54:47 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Waiman Long <longman@...hat.com>, Christoph Hellwig <hch@....de>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        Linux-sh list <linux-sh@...r.kernel.org>,
        linux-mips@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
        sparclinux <sparclinux@...r.kernel.org>,
        linux-riscv@...ts.infradead.org,
        Linux-Arch <linux-arch@...r.kernel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        linux-c6x-dev@...ux-c6x.org,
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        "the arch/x86 maintainers" <x86@...nel.org>,
        "moderated list:H8/300 ARCHITECTURE" 
        <uclinux-h8-devel@...ts.sourceforge.jp>,
        linux-xtensa@...ux-xtensa.org, Arnd Bergmann <arnd@...db.de>,
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        nios2-dev@...ts.rocketboards.org,
        Andrew Morton <akpm@...ux-foundation.org>,
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Subject: Re: [PATCH v4 2/3] locking/rwsem: Remove rwsem-spinlock.c & use
 rwsem-xadd.c for all archs

On Wed, Feb 13, 2019 at 11:01 PM Waiman Long <longman@...hat.com> wrote:
> Currently, we have two different implementation of rwsem:
>  1) CONFIG_RWSEM_GENERIC_SPINLOCK (rwsem-spinlock.c)
>  2) CONFIG_RWSEM_XCHGADD_ALGORITHM (rwsem-xadd.c)
>
> As we are going to use a single generic implementation for rwsem-xadd.c
> and no architecture-specific code will be needed, there is no point
> in keeping two different implementations of rwsem. In most cases, the
> performance of rwsem-spinlock.c will be worse. It also doesn't get all
> the performance tuning and optimizations that had been implemented in
> rwsem-xadd.c over the years.
>
> For simplication, we are going to remove rwsem-spinlock.c and make all
> architectures use a single implementation of rwsem - rwsem-xadd.c.
>
> All references to RWSEM_GENERIC_SPINLOCK and RWSEM_XCHGADD_ALGORITHM
> in the code are removed.
>
> Suggested-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Waiman Long <longman@...hat.com>

Note that this conflicts with "[PATCH 03/11] kernel/locks: consolidate
RWSEM_GENERIC_* options"
https://lore.kernel.org/lkml/20190213174005.28785-4-hch@lst.de/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds