linux-kernel - Re: [RFC PATCH v4 4/9] printk-rb: initialize new descriptors as invalid

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Message-ID: <20190820092337.cudkfdfhsu44vlhh@pathway.suse.cz>
Date:   Tue, 20 Aug 2019 11:23:37 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     linux-kernel@...r.kernel.org,
        Andrea Parri <andrea.parri@...rulasolutions.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [RFC PATCH v4 4/9] printk-rb: initialize new descriptors as
 invalid

On Thu 2019-08-08 00:32:29, John Ogness wrote:
> Initialize never-used descriptors as permanently invalid so there

The word "permanently" is confusing. It suggests that it will
never ever be valid again. I would just remove the word.

> is no risk of the descriptor unexpectedly being determined as
> valid due to dataring head overflowing/wrapping.

Please, provide more details about the solved race. Is it because
some reader could have reference to an invalid (reused) descriptor?
Can be these invalid descriptors be member of the list?

Also it might be worth to mention where is the check that might
detect such invalid descriptors and what will be the consequences.
Well, this might be clear from the race description.

Best Regards,
Petr