linux-kernel - Re: [PATCH printk v1 01/13] printk: rename cpulock functions

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Message-ID: <YgbPcAHgC1FLRXdR@hirez.programming.kicks-ass.net>
Date:   Fri, 11 Feb 2022 22:04:48 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marco Elver <elver@...gle.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Alexander Potapenko <glider@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Nicholas Piggin <npiggin@...il.com>
Subject: Re: [PATCH printk v1 01/13] printk: rename cpulock functions

On Fri, Feb 11, 2022 at 03:57:27PM -0500, Steven Rostedt wrote:
> On Fri, 11 Feb 2022 15:48:08 +0106
> John Ogness <john.ogness@...utronix.de> wrote:
> 
> > It is because (as in the example above), taking this "lock" does not
> > provide synchronization to data. It is only synchronizing between
> > CPUs. It was Steven's suggestion to call the thing a cpu_sync object and
> > nobody in the RT Track seemed to disagree.
> 
> I love causing trouble ;-)
> 
> Actually, it wasn't just my suggestion. IIRC, I believe Peter Zijlstra was
> against calling it a lock (Peter, you can use lore to see the context here).

All I remember is that it was in a room and I was late, I can't even
remember what City we were all in at the time. Was this Lisbon?

Anyway, as Steve said, it isn't really a strict exclusion thing, it only
avoids the most egregious inter-cpu interleaving. I'm down with
goldi-locks, something has to have that name :-)