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Date:   Wed, 26 Jun 2019 23:16:10 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     John Ogness <john.ogness@linutronix.de>
Cc:     Petr Mladek <pmladek@suse.com>, linux-kernel@vger.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Andrea Parri <andrea.parri@amarulasolutions.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [RFC PATCH v2 1/2] printk-rb: add a new printk ringbuffer
 implementation
Message-ID: <20190626211610.GY7905@worktop.programming.kicks-ass.net>
References: <20190607162349.18199-1-john.ogness@linutronix.de>
 <20190607162349.18199-2-john.ogness@linutronix.de>
 <20190621140516.h36g4in26pe3rmly@pathway.suse.cz>
 <87d0j31iyc.fsf@linutronix.de>
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On Mon, Jun 24, 2019 at 10:33:15AM +0200, John Ogness wrote:
> Here are the writer-relevant memory barriers and their associated
> variables:
> 
> MB1: data_list.oldest
> MB2: data_list.newest
> MB3: data_block.id
> MB4: descr.data_next
> MB5: descr_list.newest
> MB6: descr.next

I think this is the fundamental divergence in parlance.

You seem to associate a barrier with a (single) variable, where normally
a barrier is between two (or more) variables.

As you wrote in that other email (I'm stlil going through all that);
your MB5 isn't desc_list.newest, but rather between desc_list.newest and
descr.next.

Remember, the topic is called 'memory ordering', and you cannot order
singles.