From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759716Ab2FUSjb (ORCPT ); Thu, 21 Jun 2012 14:39:31 -0400 Received: from perches-mx.perches.com ([206.117.179.246]:51947 "EHLO labridge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759345Ab2FUSja (ORCPT ); Thu, 21 Jun 2012 14:39:30 -0400 Message-ID: <1340303969.22218.9.camel@joe2Laptop> Subject: Re: [PATCH] printk: Add printk_flush() to force buffered text to console From: Joe Perches To: Steven Rostedt Cc: Greg Kroah-Hartman , Ingo Molnar , Fengguang Wu , LKML , Linus Torvalds , "kay.sievers" , "Paul E. McKenney" , Ingo Molnar , Andrew Morton Date: Thu, 21 Jun 2012 11:39:29 -0700 In-Reply-To: <1340303360.27036.194.camel@gandalf.stny.rr.com> References: <20120614154153.GD17140@kroah.com> <1339693625.13377.242.camel@gandalf.stny.rr.com> <20120615042233.GA10973@localhost> <20120615043017.GA9587@kroah.com> <20120615120430.GB23681@gmail.com> <20120615231318.GD8205@kroah.com> <1339804415.25903.63.camel@gandalf.stny.rr.com> <20120618230337.GB23627@kroah.com> <1340069326.25903.177.camel@gandalf.stny.rr.com> <20120620122549.GA10561@gmail.com> <20120621171338.GF3270@kroah.com> <1340300509.27036.185.camel@gandalf.stny.rr.com> <1340302623.22065.9.camel@joe2Laptop> <1340303360.27036.194.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.2- Content-Transfer-Encoding: 7bit Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2012-06-21 at 14:29 -0400, Steven Rostedt wrote: > On Thu, 2012-06-21 at 11:17 -0700, Joe Perches wrote: > > On Thu, 2012-06-21 at 13:41 -0400, Steven Rostedt wrote: [] > > > I'm playing around with making a KERN_FLUSH "". Think that's a better > > > approach? > > > > I don't think that's better. I think it's worse > > because it intermixes the idea of a kernel message > > logging level with a specific functionality to > > emit any fragmentary message immediately. > > Are you using a 50 char width terminal? Nope. Just an old habit. > > > > I think a global setting via a some functions like: > > > > (printk private variable) > > bool printk_buffered = true; > > > > bool printk_set_buffering(bool enable) > > { > > bool old_state = printk_buffered; > > printk_buffered = enable; > > > > return old_state; > > } > > > > and maybe: > > > > bool printk_get_buffering(void) > > { > > return printk_buffered; > > } > > > > would be better because the non-buffered use should > > really be pretty isolated to last_breath type output > > and to pretty isolated cases like your long running > > tests. > > > > A separate printk_flush() function if really necessary > > but sprinkling a bunch of printk_flush() calls seems > > wasteful. > > A global buffering disable may cause other things that are printed to be > screwed up. After Kay's deferral patch (an actual improvement), lots of output could have been changed. Turning off buffering would simply revert to pre 3.5 behavior. I don't think that's a significant issue. > Something that actually expects to be buffered. There is nothing today that _expects_ buffering or is guaranteed non-buffered. The locations that benefit from non-buffering are few and isolated. > Or perhaps have printk_flush() become a new printk. That is, > printk_flush("this does not buffer"). Yuck. Then there'd be all the likely variants for prefix [pr|dev|netdev]_[_once|_ratelimited] postfix too.