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 for kexec@lists.infradead.org; Mon, 29 Mar 2021 15:10:30 +0000
From: John Ogness <john.ogness@linutronix.de>
Subject: Re: [PATCH next v1 2/3] printk: remove safe buffers
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Date: Mon, 29 Mar 2021 17:10:02 +0200
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To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>, Sergey Senozhatsky <sergey.senozhatsky@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, Thomas Gleixner <tglx@linutronix.de>, linux-kernel@vger.kernel.org, Michael Ellerman <mpe@ellerman.id.au>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Paul Mackerras <paulus@samba.org>, Eric Biederman <ebiederm@xmission.com>, Nicholas Piggin <npiggin@gmail.com>, Christophe Leroy <christophe.leroy@csgroup.eu>, Alistair Popple <alistair@popple.id.au>, Jordan Niethe <jniethe5@gmail.com>, Peter Zijlstra <peterz@infradead.org>, =?utf-8?Q?C=C3=A9dric?= Le Goater <clg@kaod.org>, Andrew Morton <akpm@linux-foundation.org>, Kees Cook <keescook@chromium.org>, Yue Hu <huyue2@yulong.com>, Alexey Kardashevskiy <aik@ozlabs.ru>, Rafael Aquini <aquini@redhat.com>, Tiezhu Yang <yangtiezhu@loongson.cn>, "Guilherme G.
 Piccoli" <gpiccoli@canonical.com>, "Paul E. McKenney" <paulmck@kernel.org>, linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org

On 2021-03-29, Petr Mladek <pmladek@suse.com> wrote:
> I wonder if some console drivers rely on the fact that the write()
> callback is called with interrupts disabled.
>
> IMHO, it would be a bug when any write() callback expects that
> callers disabled the interrupts.

Agreed.

> Do you plan to remove the console-spinning stuff after offloading
> consoles to the kthreads?

Yes. Although a similar concept will be introduced to allow the threaded
printers and the atomic consoles to compete.

> Will you call console write() callback with irq enabled from the
> kthread?

No. That defeats the fundamental purpose of this entire rework
excercise. ;-)

> Anyway, we should at least add a comment why the interrupts are
> disabled.

I decided to move the local_irq_save/restore inside the console-spinning
functions and added a comment for v2.

John Ogness

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