linux-kernel - Re: [PATCH printk v2 00/12] implement threaded console printing

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Message-ID: <87sfqrrzph.fsf@jogness.linutronix.de>
Date:   Tue, 05 Apr 2022 23:30:10 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Marco Elver <elver@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Alexander Potapenko <glider@...gle.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Nicholas Piggin <npiggin@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Kees Cook <keescook@...omium.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Wei Liu <wei.liu@...nel.org>,
        Xiaoming Ni <nixiaoming@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Helge Deller <deller@....de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Shawn Guo <shawn.guo@...aro.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Phil Auld <pauld@...hat.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Wang Qing <wangqing@...o.com>, rcu@...r.kernel.org
Subject: Re: [PATCH printk v2 00/12] implement threaded console printing

On 2022-04-05, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:
> From the list of patches and the only one I am Cc'ed to I can't find
> the answer to my question,

It seems lore is having trouble picking up the series. Until then, I've
pushed the series to github.com so you can see the code.

> i.e. does it take care about console_unregister() cases at run time?
> (We have some drivers to call ->exit() for console in that case,
> perhaps it should do something before calling it.)

Yes. In console_unregister(), the printing thread is shutdown before the
actual console unregistration takes place. The thread is shutdown here:

https://github.com/Linutronix/linux/blob/b27eb6c3d168d608b3a9d04578e030a3d79d889a/kernel/printk/printk.c#L3393

The console's exit() callback is below that:

https://github.com/Linutronix/linux/blob/b27eb6c3d168d608b3a9d04578e030a3d79d889a/kernel/printk/printk.c#L3429

> Would be nice to see some pointers where I can find the answer and
> maybe even describing in the cover-letter/commit
> message/documentation.

I suppose for the console thread patch [0] I could add a paragraph to
the commit message mentioning kernel thread shutdown for console
unregistration.

[0] https://github.com/Linutronix/linux/commit/e26ae677da2e339dd268c1f871b81e61e782393f

John