Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932583AbZJPPe3 (ORCPT ); Fri, 16 Oct 2009 11:34:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759545AbZJPPe3 (ORCPT ); Fri, 16 Oct 2009 11:34:29 -0400 Received: from az33egw02.freescale.net ([192.88.158.103]:59267 "EHLO az33egw02.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760612AbZJPPe2 (ORCPT ); Fri, 16 Oct 2009 11:34:28 -0400 Date: Fri, 16 Oct 2009 10:33:30 -0500 From: Scott Wood To: Benjamin Herrenschmidt Cc: Christian Borntraeger , linuxppc-dev@ozlabs.org, brueckner@linux.vnet.ibm.com, Timur Tabi , Alan Cox , Linux Kernel Mailing List Subject: Re: [PATCH] hvc_console: returning 0 from put_chars is not an error Message-ID: <20091016153330.GB11838@loki.buserror.net> References: <1255557226-4403-1-git-send-email-timur@freescale.com> <200910151305.47100.borntraeger@de.ibm.com> <20091015160906.GA3730@loki.buserror.net> <200910152041.26646.borntraeger@de.ibm.com> <4AD770A9.6070509@freescale.com> <1255668405.19032.13.camel@pasglop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1255668405.19032.13.camel@pasglop> User-Agent: Mutt/1.5.19 (2009-01-05) X-Brightmail-Tracker: AAAAAQAAAWE= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1142 Lines: 27 On Fri, Oct 16, 2009 at 03:46:45PM +1100, Benjamin Herrenschmidt wrote: > On Thu, 2009-10-15 at 13:57 -0500, Scott Wood wrote: > > I'd say the dropping approach is quite undesirable (significant > > potential for output loss unless the buffer is huge), unless there's > > simply no way to safely spin. Hopefully there are no such backends, but > > if there are perhaps we can have them return some special code to > > indicate that. > > Should never spin. Why is a hypervisor console different than a serial port in this regard? > Best is to keep a copy in the upper layer of the pending data and throttle > (not accept further data from tty layer) until we have managed to flush > out that "pending" buffer. The data isn't coming from the tty layer -- we're talking about printk. How do you throttle that without spinning? I agree that it shouldn't spin when handling tty I/O. -Scott -- 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/