Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933358AbYBVHlK (ORCPT ); Fri, 22 Feb 2008 02:41:10 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754093AbYBVHkx (ORCPT ); Fri, 22 Feb 2008 02:40:53 -0500 Received: from brick.kernel.dk ([87.55.233.238]:14783 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759905AbYBVHkv (ORCPT ); Fri, 22 Feb 2008 02:40:51 -0500 Date: Fri, 22 Feb 2008 08:40:48 +0100 From: Jens Axboe To: Andrew Morton Cc: KAMEZAWA Hiroyuki , Kamalesh Babulal , Linux Kernel Mailing List , linuxppc-dev@ozlabs.org, Ingo Molnar , Srivatsa Vaddagiri , Dhaval Giani , Andy Whitcroft , Balbir Singh Subject: Re: [BUG] Linux 2.6.25-rc2 - Regression from 2.6.24-rc1-git1 softlockup while bootup on powerpc Message-ID: <20080222074048.GA23197@kernel.dk> References: <47B67E5E.4010001@linux.vnet.ibm.com> <20080217192913.GO23197@kernel.dk> <20080219170432.9c04376f.kamezawa.hiroyu@jp.fujitsu.com> <20080219083633.GN23197@kernel.dk> <20080221232418.b93db8d9.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080221232418.b93db8d9.akpm@linux-foundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1392 Lines: 34 On Thu, Feb 21 2008, Andrew Morton wrote: > On Tue, 19 Feb 2008 09:36:34 +0100 Jens Axboe wrote: > > > But I think the radix 'scan over entire tree' is a bit fragile. > > eek, it had better not be. Was this an error in the caller? Hope so. The cfq use of it, not the radix tree code! It juggled the keys and wants to make sure that we see all users, modulo raced added ones (ok if we see them, doesn't matter if we don't). > > This > > patch adds a parallel hlist for ease of properly browsing the members, > > Even though io_contexts are fairly uncommon, adding more stuff to a data > structure was a pretty sad alternative to fixing a bug in > radix_tree_gang_lookup(), or to fixing a bug in a caller of it. > > IOW: what exactly went wrong here?? I could not convince myself that the current code would always do the right thing. We should not have been seeing ->key == NULL entries in there, it implied a double exit of that process. So I decided to fix it by making the code a lot more readable (the patch in question deleted a lot more than it added), at the cost of that hlist head + node. -- Jens Axboe -- 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/