From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Machek Subject: Re: [PATCH] serial: remove "too much work for irq" printk Date: Sun, 13 Jan 2008 23:03:27 +0100 Message-ID: <20080113220327.GB5128@elf.ucw.cz> References: <20080112201543.GB12775@kvack.org> <20080112212457.3bf534af@lxorguk.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from gprs189-60.eurotel.cz ([160.218.189.60]:33110 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753885AbYAMWDb (ORCPT ); Sun, 13 Jan 2008 17:03:31 -0500 Content-Disposition: inline In-Reply-To: <20080112212457.3bf534af@lxorguk.ukuu.org.uk> Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Alan Cox Cc: Benjamin LaHaise , akpm@osdl.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org On Sat 2008-01-12 21:24:57, Alan Cox wrote: > On Sat, 12 Jan 2008 15:15:43 -0500 > Benjamin LaHaise wrote: > > > When using kvm with a serial console, the serial driver will print out > > "too much work for irq4" on any heavy activity (ie vi on a file repainting > > the terminal). This message is entirely spurious, as output continues to > > work fine. Remove the message as it corrupts screen output and is far too > > easy to trigger. > > NAK. This is a qemu/kvm emulation bug. The real check is there to catched > jammed IRQs and combined with the IRQ bug handling nowdays does actually > do the intended job. > > Our serial port code (correctly) interprets a continuous stream of bytes > at an impossible bit rate as an error. KVM should be emulating to some > extent at least the timing on serial interfaces or using a virtualised > interface. How can you tell apart impossible bit rate from really slow CPU, or maybe just an SMI storm, or heavy busmaster DMA? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html