linux-kernel - Re: [RFC PATCH v1 19/25] printk: introduce emergency messages

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Message-ID: <20190312025847.GD4146@jagdpanzerIV>
Date:   Tue, 12 Mar 2019 11:58:47 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        John Ogness <john.ogness@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Wang <wonderfly@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Jiri Slaby <jslaby@...e.com>,
        Peter Feiner <pfeiner@...gle.com>,
        linux-serial@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: Re: [RFC PATCH v1 19/25] printk: introduce emergency messages

On (03/08/19 11:31), Petr Mladek wrote:
> Great catch!
> 
> I think that it is doable to guard the list using RCU.

I think console_sem is more than just list lock.

E.g. fb_flashcursor() - console_sem protects framebuffer from concurrent
modifications. And many other examples.

I think the last time we talked about it (two+ years ago) we counted
5 or 7 (don't remember exactly) different things which console_sem
does.

	-ss