linux-kernel - Re: [PATCH v3] printk: Add console owner and waiter logic to load balance console writes

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Message-ID: <20171103075456.15cd811e@vmware.local.home>
Date:   Fri, 3 Nov 2017 07:54:56 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...e.de>, Michal Hocko <mhocko@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        "yuwang.yuwang" <yuwang.yuwang@...baba-inc.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Jan Kara <jack@...e.cz>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Subject: Re: [PATCH v3] printk: Add console owner and waiter logic to load
 balance console writes

On Fri, 3 Nov 2017 07:54:04 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> The new waiter gets set only if there isn't already a waiter *and*
> there is an owner that is not current (and with the printk_safe_enter I
> don't think that is even needed).
> 
> +				while (!READ_ONCE(console_waiter))
> +					cpu_relax();

I still need to fix the patch. I cut and pasted the bad version. This
should have been:

	while (READ_ONCE(console_waiter))
		cpu_relax();

-- Steve