From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f181.google.com (mail-pd0-f181.google.com [209.85.192.181]) by kanga.kvack.org (Postfix) with ESMTP id 426DD6B0038 for ; Sun, 12 Oct 2014 13:20:17 -0400 (EDT) Received: by mail-pd0-f181.google.com with SMTP id z10so4371544pdj.40 for ; Sun, 12 Oct 2014 10:20:16 -0700 (PDT) Received: from shards.monkeyblade.net (shards.monkeyblade.net. [2001:4f8:3:36:211:85ff:fe63:a549]) by mx.google.com with ESMTP id aj8si8436232pad.241.2014.10.12.10.20.15 for ; Sun, 12 Oct 2014 10:20:16 -0700 (PDT) Date: Sun, 12 Oct 2014 13:20:12 -0400 (EDT) Message-Id: <20141012.132012.254712930139255731.davem@davemloft.net> Subject: Re: unaligned accesses in SLAB etc. From: David Miller In-Reply-To: <20141011.221510.1574777235900788349.davem@davemloft.net> References: <20141011.221510.1574777235900788349.davem@davemloft.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, linux-mm@kvack.org, mroos@linux.ee, sparclinux@vger.kernel.org From: David Miller Date: Sat, 11 Oct 2014 22:15:10 -0400 (EDT) > > I'm getting tons of the following on sparc64: > > [603965.383447] Kernel unaligned access at TPC[546b58] free_block+0x98/0x1a0 > [603965.396987] Kernel unaligned access at TPC[546b60] free_block+0xa0/0x1a0 > [603965.410523] Kernel unaligned access at TPC[546b58] free_block+0x98/0x1a0 The unaligned accesses are happening in the SLAB_OBJ_PFMEMALLOC code, which assumes that all object pointers are "unsigned long" aligned: static inline void set_obj_pfmemalloc(void **objp) { *objp = (void *)((unsigned long)*objp | SLAB_OBJ_PFMEMALLOC); return; } etc. etc. But that code has been there working forever. Something changed recently such that this assumption no longer holds. In all of the cases, the address is 4-byte aligned but not 8-byte aligned. And they are vmalloc addresses. Which made me suspect the percpu commit: ==================== commit bf0dea23a9c094ae869a88bb694fbe966671bf6d Author: Joonsoo Kim Date: Thu Oct 9 15:26:27 2014 -0700 mm/slab: use percpu allocator for cpu cache ==================== And indeed, reverting this commit fixes the problem. -- 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