From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f175.google.com (mail-pd0-f175.google.com [209.85.192.175]) by kanga.kvack.org (Postfix) with ESMTP id 589B16B0038 for ; Fri, 20 Mar 2015 18:49:37 -0400 (EDT) Received: by pdbop1 with SMTP id op1so121272308pdb.2 for ; Fri, 20 Mar 2015 15:49:37 -0700 (PDT) Received: from userp1040.oracle.com (userp1040.oracle.com. [156.151.31.81]) by mx.google.com with ESMTPS id fn4si11467095pab.203.2015.03.20.15.49.36 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Mar 2015 15:49:36 -0700 (PDT) Message-ID: <550CA3F9.9040201@oracle.com> Date: Fri, 20 Mar 2015 16:49:29 -0600 From: David Ahern MIME-Version: 1.0 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 Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: linux-mm , LKML 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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org