Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754617AbXJaG4Q (ORCPT ); Wed, 31 Oct 2007 02:56:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751540AbXJaG4D (ORCPT ); Wed, 31 Oct 2007 02:56:03 -0400 Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:46078 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1751326AbXJaG4B (ORCPT ); Wed, 31 Oct 2007 02:56:01 -0400 Date: Tue, 30 Oct 2007 23:56:00 -0700 (PDT) Message-Id: <20071030.235600.254712083.davem@davemloft.net> To: npiggin@suse.de Cc: duaneg@dghda.com, mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: 2.6.23 regression: accessing invalid mmap'ed memory from gdb causes unkillable spinning From: David Miller In-Reply-To: <20071031064221.GC12189@wotan.suse.de> References: <20071031064221.GC12189@wotan.suse.de> X-Mailer: Mew version 5.2 on Emacs 22.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1601 Lines: 36 From: Nick Piggin Date: Wed, 31 Oct 2007 07:42:21 +0100 > Sysrq+T fails to show the stack trace of a running task. Presumably this > is to avoid a garbled stack, however it can often be useful, and besides > there is no guarantee that the task won't start running in the middle of > show_stack(). If there are any correctness issues, then the archietcture > would have to take further steps to ensure the task is not running. > > Signed-off-by: Nick Piggin This is useful. Even more useful would be a show_regs() on the cpu where running tasks are running. If not a full show_regs() at least a program counter. That's usually what you're trying to debug and we provide nearly no way to handle: some task is stuck in a loop in kernel mode and you need to know exactly where that is. This is pretty easy to do on sparc64. In fact I can capture remote cpu registers even when that CPU's interrupts are disabled. I suppose other arches could do a NMI'ish register capture like this as well. I have a few bug reports that I can't make more progress on because I currently can't ask users to do something to fetch the registers on the seemingly hung processor. This is why I'm harping on this so much :-) Anyways, my core suggestion is to add a hook here so platforms can do the remote register fetch if they want. - 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/