Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756857AbYCKMD4 (ORCPT ); Tue, 11 Mar 2008 08:03:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755920AbYCKMDq (ORCPT ); Tue, 11 Mar 2008 08:03:46 -0400 Received: from rv-out-0910.google.com ([209.85.198.189]:43163 "EHLO rv-out-0910.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756086AbYCKMDa (ORCPT ); Tue, 11 Mar 2008 08:03:30 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=QotRyYCN5Xcm971SBVy4b1GRJT8p3yHQ0mgIkOK3nyQf5Ku8indShqO0inf2oO4t1C64YothZJYoXKfaesjZoApPW8ChjlrjvQTXBIr3Ns/aPsiYnMnmEOvEXXKBbUO3W4fa6EOatu9Z6esM+N81GSjcfh7Em5SLow68EzZ8jbc= Message-ID: Date: Tue, 11 Mar 2008 13:03:29 +0100 From: "Zdenek Kabelac" To: "Andi Kleen" Subject: Re: [PATCH REPOST] Run IST traps from user mode preemptive on process stack Cc: "Ingo Molnar" , tglx@linutronix.de, linux-kernel@vger.kernel.org, jkosina@suse.cz In-Reply-To: <20080311012432.GA28576@basil.nowhere.org> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20080311012432.GA28576@basil.nowhere.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1624 Lines: 46 2008/3/11, Andi Kleen : > Run IST traps from user mode preemptive on process stack > > [Repost. Please ack or nack. -Andi] > > x86-64 has a few exceptions which run on special architecture > supported IST exception stacks: these are nmi, double fault, stack fault, > int 3, debug. > > Previously they would check for a scheduling event on returning > if the original CPU state was user mode and then switch to a > process stack to schedule. > > But the actual trap handler would still run on the IST stack > with preemption disabled. > Hi Andi In my post where I've been showing BUG trace: http://lkml.org/lkml/2008/3/10/157 I've mentioned my problem with busy looping in Qemu. I'm not sure whether this is good or bad sign - but with this patch you have posted, I do not have to wait in qemu for minutes to get the 'busy-loop' - I get the exact same loop almost instantly when I start disk read of LV partition and running my simple module insertion testcase. > This patch changes these traps instead to always switch > to the process stack when the trap originated from user mode. > For kernel traps it keeps running non preemptive on the IST stack > because that is much safer (e.g. to still get nmi watchdog events > out even when the process stack is corrupted) > So what should I check to get fixed my problem in qemu ? Zdenek -- 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/