linux-kernel - Re: [RFC][PATCH v8 1/2] printk: Make printk() completely async

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Message-ID: <20160329091439.GC12993@quack.suse.cz>
Date:	Tue, 29 Mar 2016 11:14:39 +0200
From:	Jan Kara <jack@...e.cz>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.com>, Petr Mladek <pmladek@...e.com>,
	Tejun Heo <tj@...nel.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-kernel@...r.kernel.org,
	Byungchul Park <byungchul.park@....com>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	Jan Kara <jack@...e.cz>
Subject: Re: [RFC][PATCH v8 1/2] printk: Make printk() completely async

On Fri 25-03-16 00:43:22, Sergey Senozhatsky wrote:
> @@ -1655,6 +1670,14 @@ asmlinkage int vprintk_emit(int facility, int level,
>  	raw_spin_lock(&logbuf_lock);
>  	logbuf_cpu = this_cpu;
>  
> +	/*
> +	 * Set printing kthread sleep condition early, under the
> +	 * logbuf_lock, so it (if RUNNING) will go to console_lock()
> +	 * and spin on logbuf_lock.
> +	 */
> +	if (!in_panic && printk_kthread && !need_flush_console)
> +		need_flush_console = true;
> +
>  	if (unlikely(recursion_bug)) {
>  		static const char recursion_msg[] =
>  			"BUG: recent printk recursion!";

I like the cleaned up need_flush_console handling! Just a suggestion: It
may be more logical to handle need_flush_console setting under logbuf_lock
but after we actually store the message in the buffer, not before. Doesn't
matter for correctness now but may be more future-proof.

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR