From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=cAsB=DB=vger.kernel.org=linux-kernel-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,
	HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS
	autolearn=no autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id E3D1CC4363D
	for <linux-kernel@archiver.kernel.org>; Thu, 24 Sep 2020 16:09:03 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [23.128.96.18])
	by mail.kernel.org (Postfix) with ESMTP id 91FD623600
	for <linux-kernel@archiver.kernel.org>; Thu, 24 Sep 2020 16:09:03 +0000 (UTC)
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1728597AbgIXQJC (ORCPT
        <rfc822;linux-kernel@archiver.kernel.org>);
        Thu, 24 Sep 2020 12:09:02 -0400
Received: from smtprelay0079.hostedemail.com ([216.40.44.79]:52590 "EHLO
        smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL)
        by vger.kernel.org with ESMTP id S1728448AbgIXQJC (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 24 Sep 2020 12:09:02 -0400
Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60])
        by smtprelay05.hostedemail.com (Postfix) with ESMTP id DC11718029143;
        Thu, 24 Sep 2020 16:09:00 +0000 (UTC)
X-Session-Marker: 6A6F6540706572636865732E636F6D
X-HE-Tag: toe09_3205d4c27160
X-Filterd-Recvd-Size: 1971
Received: from XPS-9350.home (unknown [47.151.133.149])
        (Authenticated sender: joe@perches.com)
        by omf12.hostedemail.com (Postfix) with ESMTPA;
        Thu, 24 Sep 2020 16:08:58 +0000 (UTC)
Message-ID: <c0dbf88bb7ca4d77ed0576ced82302b81aebe664.camel@perches.com>
Subject: Re: [PATCH] x86/irq: Use printk_deferred() on raw_spin_lock()
 protected sections
From:   Joe Perches <joe@perches.com>
To:     Peter Zijlstra <peterz@infradead.org>,
        Daniel Bristot de Oliveira <bristot@redhat.com>
Cc:     x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>, Marc Zyngier <maz@kernel.org>,
        Peter Xu <peterx@redhat.com>,
        Andy Lutomirski <luto@kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        linux-kernel@vger.kernel.org
Date:   Thu, 24 Sep 2020 09:08:57 -0700
In-Reply-To: <20200924102822.GA2628@hirez.programming.kicks-ass.net>
References: <e68888438cec9a1da53aaa1647720ade638d6ad4.1600705105.git.bristot@redhat.com>
         <20200924102822.GA2628@hirez.programming.kicks-ass.net>
Content-Type: text/plain; charset="ISO-8859-1"
User-Agent: Evolution 3.36.4-0ubuntu1 
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 2020-09-24 at 12:28 +0200, Peter Zijlstra wrote:
> On Mon, Sep 21, 2020 at 06:22:12PM +0200, Daniel Bristot de Oliveira wrote:
> > While testing hotplug I got this BUG:
> > It was caused by printk() inside a code section protected by a
> > raw_spin_lock() that ended up calling a serial console that
> > uses a regular spin_lock().
> > 
> > Use the printk_deferred() to avoid calling the serial console
> > in a raw_spin_lock() protected section.
> 
> I consider printk_deferred() to be a bug, can't we just wait for the new
> printk implementation to land so we don't need all this nonsense?

It will be good to do a sed fixup for all these
printk_deferred uses soon,  but in the meantime
isn't it useful to avoid BUGs?