Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030401AbXBZSUc (ORCPT ); Mon, 26 Feb 2007 13:20:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030403AbXBZSUc (ORCPT ); Mon, 26 Feb 2007 13:20:32 -0500 Received: from smtp.osdl.org ([65.172.181.24]:55852 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030401AbXBZSUb (ORCPT ); Mon, 26 Feb 2007 13:20:31 -0500 Date: Mon, 26 Feb 2007 10:13:49 -0800 (PST) From: Linus Torvalds To: Oleg Nesterov cc: Stephane Eranian , linux-kernel@vger.kernel.org Subject: Re: bug in kernel 2.6.21-rc1-git1: conventional floppy drive cannot be mounted without hanging up the whole system In-Reply-To: <20070226180635.GA644@tv-sign.ru> Message-ID: References: <20070226180635.GA644@tv-sign.ru> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1624 Lines: 38 On Mon, 26 Feb 2007, Oleg Nesterov wrote: > > I know nothing about floppy, but I guess the reason is floppy_disable_hlt(). > > Sorry for the offtopic question, is it really needed? According to grep, floppy > is the only one user of disable_hlt(). I suspect you'd have a hard time finding a machine where it was broken any more. But it used to be that the native (aka "braindamaged and idiotic") DMA by the motherboard southbridge chipset (and apparently _only_ that) had problems with the CPU being halted on some motherboards, and would corrupt data if the CPU was halted while the DMA took place. We never bothered to even figure out why it happened, though. It was undeniable that there were people who had trouble with "hlt" and the floppy driver, but it is not clear what the cause was. That's a _loong_ time ago, though, and it *probably* hasn't been an issue on any recent machine. People just don't care enough to test, especially since the upside is negligible, and the downside for when it would trigger is huge. The floppy is still pretty much the only user of native motherboard (aka i8237) DMA'ing for most people. Some old ISA sound-cards may do it, of course. But any PCI device will do its own DMA rather than rely on the broken 8237 DMA engine, so for all I know, the bug - whatever it ever ended up being - could still be there. Linus - 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/