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 S932763Ab2FUSRG (ORCPT <rfc822;w@1wt.eu>);
	Thu, 21 Jun 2012 14:17:06 -0400
Received: from perches-mx.perches.com ([206.117.179.246]:45234 "EHLO
	labridge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP
	id S932745Ab2FUSRE (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Thu, 21 Jun 2012 14:17:04 -0400
Message-ID: <1340302623.22065.9.camel@joe2Laptop>
Subject: Re: [PATCH] printk: Add printk_flush() to force buffered text to
 console
From: Joe Perches <joe@perches.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Ingo Molnar <mingo@kernel.org>, Fengguang Wu <fengguang.wu@intel.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "kay.sievers" <kay.sievers@vrfy.org>,
        "Paul E. McKenney" <paulmck@us.ibm.com>, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>
Date: Thu, 21 Jun 2012 11:17:03 -0700
In-Reply-To: <1340300509.27036.185.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>
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: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 2012-06-21 at 13:41 -0400, Steven Rostedt wrote:
> On Thu, 2012-06-21 at 10:13 -0700, Greg Kroah-Hartman wrote:
> 
> > > So mind re-sending the latest version of your printk flushing 
> > > fix? I'll apply it for v3.5-rc if other trees won't pick it up.
> > 
> > I'll be glad to pick it up, just make it work properly :)
> 
> I'm playing around with making a KERN_FLUSH "<f>". 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.

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 sprinking a bunch of printk_flush() calls seems
wasteful.