Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754634AbXKAVLx (ORCPT ); Thu, 1 Nov 2007 17:11:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754322AbXKAVLp (ORCPT ); Thu, 1 Nov 2007 17:11:45 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.31.123]:58846 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754232AbXKAVLo (ORCPT ); Thu, 1 Nov 2007 17:11:44 -0400 Date: Thu, 1 Nov 2007 22:11:53 +0100 From: Pavel Machek To: Mathieu Desnoyers Cc: Tim Bird , Matt Mackall , linux kernel , Ingo Molnar , Jon Smirl Subject: Re: IRQ off latency of printk is very high Message-ID: <20071101211153.GA11074@elf.ucw.cz> References: <4720F21F.9090404@am.sony.com> <20071025222804.GA13954@Krystal> <47211E2C.90301@am.sony.com> <20071025231237.GT19691@waste.org> <472129C3.6040405@am.sony.com> <20071029185445.GA7742@ucw.cz> <20071101152714.GA2489@Krystal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20071101152714.GA2489@Krystal> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.16 (2007-06-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1363 Lines: 40 Hi! > > > It seems draconian to drain the entire buffer with ints disabled. > > > Is it possible to break this up and send out smaller chunks > > > at a time? Maybe by putting a chunk loop in release_console_sem()? > > > > Well, I believe someone got > > > > DDetetccctted ed 113223 HHzz CPUCPU > > > > in his dmesg, and now we have this 'draconian' locking. How can we > > prevent mangled messages without it? > > The main interest seems to be to protect from mixed printk output > between different CPUs in process context. I don't think it would be > that bad if interrupts come and output error messages in the middle of a > printk, isn't it ? > > therefore, could we do something like : > > > if (!in_irq()) > spin_lock(&logbuf_lock); > ... > if (!in_irq()) > spin_unlock(&logbuf_lock); > > ? (yes, this is a crazy idea) Two messages in atomic sections on different cpus could still be mixed :-). But yes, something like this may be the way to go. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/