linux-kernel - Re: [PATCH 03/10] locking/rwsem: Rename kernel/locking/rwsem.h

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Date:   Wed, 13 Feb 2019 10:47:11 -0500
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, x86@...nel.org,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>
Subject: Re: [PATCH 03/10] locking/rwsem: Rename kernel/locking/rwsem.h

On 02/13/2019 04:19 AM, Peter Zijlstra wrote:
> On Tue, Feb 12, 2019 at 07:27:00PM -0500, Waiman Long wrote:
>> The content of kernel/locking/rwsem.h is now specific to rwsem-xadd only.
>> Rename it to rwsem-xadd.h to indicate that it is specific to rwsem-xadd
>> and include it only when CONFIG_RWSEM_XCHGADD_ALGORITHM is set. As a result,
>> the CONFIG_RWSEM_XCHGADD_ALGORITHM conditional compilation directives can
>> be removed. There is no functional change.
> Since all of rwsem-xadd is now generic code; how about we delete the
> spinlock thing and keep everything rwsem ?
>
> We don't carry a special spinlock mutex implementation either. And
> arguably any arch that uses spinlock based atomics (afaict the only case
> where rwsem-spinlock makes any sense anyway) suck anyway.

I don't mind removing the rwsem-spinlock code and have just one
implementation for all as long as there is no objection from others. I
don't know the history of why we have 2 implementations of rwsem and so
I didn't plan to do that.

Cheers,
Longman