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

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Message-ID: <Ygn7ZFnFL4QiQHRg@google.com>
Date:   Mon, 14 Feb 2022 15:49:08 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.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 (22/02/11 13:44), Petr Mladek wrote:
> On Mon 2022-02-07 20:49:11, John Ogness wrote:
> > Since the printk cpulock is CPU-reentrant and since it is used
> > in all contexts, its usage must be carefully considered and
> > most likely will require programming locklessly. To avoid
> > mistaking the printk cpulock as a typical lock, rename it to
> > cpu_sync. The main functions then become:
> > 
> >     printk_cpu_sync_get_irqsave(flags);
> >     printk_cpu_sync_put_irqrestore(flags);
> 
> It is possible that I will understand the motivation later when
> reading the entire patchset. But my initial reaction is confusion ;-)
> 
> From mo POV, it is a lock. It tries to get exclusive access and
> has to wait until the current owner releases it.

printk has been using enter/exit naming for a while now (starting with
nmi enter/exit, then printk_safe enter/exit and soon direct enter/exit);
so may be we can follow suit here and use printk_cpu_sync_enter() and
printk_cpu_sync_exit()?


> After all the word "lock" is part of "deadlock".

That's a good one.