Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754628Ab1FFQN0 (ORCPT ); Mon, 6 Jun 2011 12:13:26 -0400 Received: from casper.infradead.org ([85.118.1.10]:53772 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751429Ab1FFQNY convert rfc822-to-8bit (ORCPT ); Mon, 6 Jun 2011 12:13:24 -0400 Subject: Re: [debug patch] printk: Add a printk killswitch to robustify NMI watchdog messages From: Peter Zijlstra To: Ingo Molnar Cc: Arne Jansen , Linus Torvalds , mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, efault@gmx.de, npiggin@kernel.dk, akpm@linux-foundation.org, frank.rowand@am.sony.com, tglx@linutronix.de, linux-tip-commits@vger.kernel.org In-Reply-To: <20110606160810.GA16636@elte.hu> References: <4DEB8A93.30601@die-jansens.de> <20110605141003.GB29338@elte.hu> <4DEB933C.1070900@die-jansens.de> <20110605151323.GA30590@elte.hu> <1307349530.2353.7374.camel@twins> <20110606145827.GD30348@elte.hu> <1307372989.2322.136.camel@twins> <1307375227.2322.161.camel@twins> <20110606155236.GA7374@elte.hu> <1307376039.2322.164.camel@twins> <20110606160810.GA16636@elte.hu> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Mon, 06 Jun 2011 18:12:51 +0200 Message-ID: <1307376771.2322.168.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1285 Lines: 32 On Mon, 2011-06-06 at 18:08 +0200, Ingo Molnar wrote: > * Peter Zijlstra wrote: > > > On Mon, 2011-06-06 at 17:52 +0200, Ingo Molnar wrote: > > > * Peter Zijlstra wrote: > > > > > > > Needs more staring at, preferably by someone who actually > > > > understands that horrid mess :/ Also, this all still doesn't make > > > > printk() work reliably while holding rq->lock. > > > > > > So, what about my suggestion to just *remove* the wakeup from there > > > and use the deferred wakeup mechanism that klogd uses. > > > > > > That would make printk() *visibly* more robust in practice. > > > > That's currently done from the jiffy tick, do you want to effectively > > delay releasing the console_sem for the better part of a jiffy? > > Yes, and we already do it in some other circumstances. We do? > Can you see > any problem with that? klogd is an utter slowpath anyway. but console_sem isn't klogd. We delay klogd and that's perfectly fine, but afaict we don't delay console_sem. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/