From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753339AbcLMB1B (ORCPT <rfc822;w@1wt.eu>);
        Mon, 12 Dec 2016 20:27:01 -0500
Received: from mail-pf0-f196.google.com ([209.85.192.196]:35997 "EHLO
        mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1752864AbcLMB1A (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Mon, 12 Dec 2016 20:27:00 -0500
Date: Tue, 13 Dec 2016 10:27:06 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
        Tejun Heo <tj@kernel.org>, Calvin Owens <calvinowens@fb.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Andy Lutomirski <luto@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Subject: Re: [RFC][PATCHv5 6/7] printk: use printk_safe buffers in printk
Message-ID: <20161213012706.GD415@jagdpanzerIV.localdomain>
References: <20161201135546.15549-1-sergey.senozhatsky@gmail.com>
 <20161201135546.15549-7-sergey.senozhatsky@gmail.com>
 <20161212163018.GE2441@pathway.suse.cz>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20161212163018.GE2441@pathway.suse.cz>
User-Agent: Mutt/1.7.2 (2016-11-26)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On (12/12/16 17:30), Petr Mladek wrote:
> On Thu 2016-12-01 22:55:45, Sergey Senozhatsky wrote:
> > Use printk_safe per-CPU buffers in printk recursion-prone blocks:
> > -- around logbuf_lock protected sections in vprintk_emit() and
> >    console_unlock()
> > -- around down_trylock_console_sem() and up_console_sem()
> > 
> > Note that this solution addresses deadlocks caused by printk()
> > recursive calls only. That is vprintk_emit() and console_unlock().
> > 
> > Another thing to note is that we now keep lockdep enabled in printk,
> > because we are protected against the printk recursion caused by lockdep
> > in vprintk_emit() by the printk-safe mechanism - we first switch to
> > per-CPU buffers and only then access the deadlock-prone locks.
> > 
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> 
> Looks fine and safe to me.
> 
> Reviewed-by: Petr Mladek <pmladek@suse.com>

thanks.

	-ss