linux-kernel - Re: [PATCH next v2 2/3] printk: change @clear_seq to atomic64

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Message-ID: <20201209081623.GI2414@hirez.programming.kicks-ass.net>
Date:   Wed, 9 Dec 2020 09:16:23 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH next v2 2/3] printk: change @clear_seq to atomic64_t

On Tue, Dec 08, 2020 at 11:36:44PM +0106, John Ogness wrote:
> For the state variable we chose atomic_long_t instead of atomic64_t for
> this reason. atomic_long_t operations are available atomically on all
> architectures.

Please put on your eye cancer gear and inspect the atomic implementation
of PA-RISC, Sparc32, feh, I forgot who else.

Those SMP capable architectures are gifted with just one XCHG like
atomic instruction :/ Anyway, as said in the other email, they also
don't have NMIs so it mostly works.