From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751799AbbCTWti (ORCPT ); Fri, 20 Mar 2015 18:49:38 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:40256 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751198AbbCTWth (ORCPT ); Fri, 20 Mar 2015 18:49:37 -0400 Message-ID: <550CA3F9.9040201@oracle.com> Date: Fri, 20 Mar 2015 16:49:29 -0600 From: David Ahern User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Linus Torvalds CC: linux-mm , LKML Subject: Re: 4.0.0-rc4: panic in free_block References: <550C37C9.2060200@oracle.com> In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: aserv0021.oracle.com [141.146.126.233] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/20/15 3:17 PM, Linus Torvalds wrote: > In other words, if I read that sparc asm right (and it is very likely > that I do *not*), then "objp" is NULL, and that's why you crash. That does appear to be why. I put a WARN_ON before clear_obj_pfmemalloc() if objpp[i] is NULL. I got 2 splats during an 'allyesconfig' build and the system stayed up. > > That's odd, because we know that objp cannot be NULL in > kmem_slab_free() (even if we allowed it, like with kfree(), > remove_vma() cannot possibly have a NULL vma, since ti dereferences it > multiple times). > > So I must be misreading this completely. Somebody with better sparc > debugging mojo should double-check my logic. How would objp be NULL? I'll add checks to higher layers and see if it reveals anything. I did ask around and apparently this bug is hit only with the new M7 processors. DaveM: that's why you are not hitting this. David