Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752858Ab3GFIHv (ORCPT ); Sat, 6 Jul 2013 04:07:51 -0400 Received: from mail-ea0-f181.google.com ([209.85.215.181]:56843 "EHLO mail-ea0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752709Ab3GFIHs (ORCPT ); Sat, 6 Jul 2013 04:07:48 -0400 Date: Sat, 6 Jul 2013 10:07:44 +0200 From: Ingo Molnar To: Frederic Weisbecker Cc: Linus Torvalds , "H. Peter Anvin" , Dave Jones , Linux Kernel , Thomas Gleixner Subject: Re: scheduling while atomic & hang. Message-ID: <20130706080744.GA1342@gmail.com> References: <20130704015525.GA8486@redhat.com> <51D5BA25.9060207@zytor.com> <20130705065113.GA6588@gmail.com> <20130706080225.GA439@somewhere> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130706080225.GA439@somewhere> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1509 Lines: 38 * Frederic Weisbecker wrote: > On Fri, Jul 05, 2013 at 12:27:51PM -0700, Linus Torvalds wrote: > > On Thu, Jul 4, 2013 at 11:51 PM, Ingo Molnar wrote: > > > > > > It would be nice to have a full-kernel-stack backtrace printout as an > > > option, which prints entries 'above' the current RSP. > > > > One problem with that is that it is likely to be mostly overwritten by > > the debug code that is about to print this all out - and any non-debug > > code may well be really old, just with a sufficiently deep stack trace > > to show up. Not to mention missing any irq-stack changes etc anyway. > > > > So it can easily be *very* misleading - I'm not sure how useful it > > would be as an idea. > > > > Linus > > So if the unwider doesn't run with the same stak than the target, it > migh work. This can work with BUG for example But I believe that WARN > doesn't do a trap in x86. Instead of switching stacks it might be better to create an early snapshot of the stack into a temporary area before calling anything, and to print that. This is debug code, so overhead is not a big issue. But yeah, Linus is right, it gets hairy, can be misleading and has limited utility :-/ Thanks, Ingo -- 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/