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Date:   Sat, 5 Dec 2020 18:41:05 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To:     Petr Mladek <pmladek@suse.com>
Cc:     John Ogness <john.ogness@linutronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-kernel@vger.kernel.org
Subject: Re: recursion handling: Re: [PATCH next v2 3/3] printk: remove
 logbuf_lock, add syslog_lock
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References: <20201201205341.3871-1-john.ogness@linutronix.de>
 <20201201205341.3871-4-john.ogness@linutronix.de>
 <X8pfX/qPBuY360k/@alley>
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On (20/12/04 17:10), Petr Mladek wrote:
> 
> One reason is the use of per-cpu variables. Alternative solution would
> be to store printk_context into task_struct.

We can keep per-CPU, disable preemption and have counters for
every context (task, soft/hard irq, NMI). Shouldn't be a problem

	vprintk_emit()
	{
		preempt_disable()
		vprintk_store()
		preempt_enable()

		preempt_disable()
		console_unlock()
		preempt_enable()
	}

vprintk_store() is a small fraction of console_unlock() time wise.

	-ss