From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932468AbbJVKQV (ORCPT ); Thu, 22 Oct 2015 06:16:21 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:42698 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754330AbbJVKQU (ORCPT ); Thu, 22 Oct 2015 06:16:20 -0400 Date: Thu, 22 Oct 2015 12:16:26 +0200 From: Peter Zijlstra To: Petr Mladek Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andrew Morton , Jiri Kosina , x86@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/spinlocks: Avoid a deadlock when someone unlock a zapped ticked spinlock Message-ID: <20151022101626.GN2508@worktop.programming.kicks-ass.net> References: <1445419089-4350-1-git-send-email-pmladek@suse.com> <20151021111120.GK17308@twins.programming.kicks-ass.net> <20151022093937.GA2599@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151022093937.GA2599@pathway.suse.cz> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 22, 2015 at 11:39:38AM +0200, Petr Mladek wrote: > Maybe, we could add support to use early console in case of Oops and > panic. But we should not do this by default. It would help, especially > when the problem is reproducible and we get stacked with the normal > console. What I typically do is route everything to 8250 early console and rip out everything printk buffer nonsense. That gets you a fairly reliable console, no locking, only vscnprintf() and OUTB banging. No printk() wanting to do wakeups and other such nonsense that doesn't work. I appreciate that might not be for everybody, but it also shouldn't be this hard to get something reliable.