linux-kernel - Re: [PATCH v2] printk: defer_console

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Message-ID: <YgnqBgzEhgZZskun@google.com>
Date:   Mon, 14 Feb 2022 14:35:02 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: [PATCH v2] printk: defer_console_output: use atomic update

On (22/02/14 14:32), Sergey Senozhatsky wrote:
> On (22/02/11 12:28), John Ogness wrote:
> > Hi Petr,
> > 
> > On 2022-02-10, Petr Mladek <pmladek@...e.com> wrote:
> > > The patch has been committed into printk/linux.git, branch for-5.18.
> > 
> > Sebastian also pointed out that the use of __this_cpu_xchg() is the same
> > problem with the same variable for the same reason. We should fold that
> > change into the patch as well. The patch will followup this message.
> 
> But that __this_cpu_xchg() (that this lol) can only be performed form the
> IRQ context. Can you please elaborate what is the problem with it?

Oh, it can race with NMI, yeah.