From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CDEC7C352A3 for ; Thu, 13 Feb 2020 19:27:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A117C218AC for ; Thu, 13 Feb 2020 19:27:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581622023; bh=TDAxW1JPHmJ/ljPAb+Jb3q13jA/imvWCMZxafWxw+xw=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=bU4NJ46BEJTahG/xGL6uEu1GejLfr2hYb7UWGADw+wjp07h76/2KH2Qp8n02QJdG/ DmpRl8/3n8yw6pu4i4bKJjCOj3ZicrFyjwQ448DLhCS8IlY1yfI9OlzmjTvlUOzDNF CKtUa2PJaS66/KfcrvKZnJLbO1SaLh3f3K63k2iY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728648AbgBMT1C (ORCPT ); Thu, 13 Feb 2020 14:27:02 -0500 Received: from mail.kernel.org ([198.145.29.99]:59398 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728137AbgBMT1C (ORCPT ); Thu, 13 Feb 2020 14:27:02 -0500 Received: from paulmck-ThinkPad-P72.home (unknown [62.84.152.189]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 48C9A2168B; Thu, 13 Feb 2020 19:27:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581622021; bh=TDAxW1JPHmJ/ljPAb+Jb3q13jA/imvWCMZxafWxw+xw=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=rTtXCX9bSozVpBQ0oFBKxi+yueKqDDXpnfbS6JEMEZXirDEUfiQtIcl7F2GPV+cId DRU5Waef1IpymCjYdJniPb1boPSycttaNrtvFoZQxoiDpfuwxgY5Ua1zsHuuUaZpcz UWv9rTQBL9yM0dYm0AWEah/jolO913xA37TNgxhk= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 5C3F73520B69; Thu, 13 Feb 2020 11:26:59 -0800 (PST) Date: Thu, 13 Feb 2020 11:26:59 -0800 From: "Paul E. McKenney" To: Qian Cai Cc: akpm@linux-foundation.org, elver@google.com, david@redhat.com, jack@suse.cz, jhubbard@nvidia.com, ira.weiny@intel.com, dan.j.williams@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -next v2] mm: annotate a data race in page_zonenum() Message-ID: <20200213192659.GJ2935@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <1581619089-14472-1-git-send-email-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1581619089-14472-1-git-send-email-cai@lca.pw> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 13, 2020 at 01:38:09PM -0500, Qian Cai wrote: > BUG: KCSAN: data-race in page_cpupid_xchg_last / put_page > > write (marked) to 0xfffffc0d48ec1a00 of 8 bytes by task 91442 on cpu 3: > page_cpupid_xchg_last+0x51/0x80 > page_cpupid_xchg_last at mm/mmzone.c:109 (discriminator 11) > wp_page_reuse+0x3e/0xc0 > wp_page_reuse at mm/memory.c:2453 > do_wp_page+0x472/0x7b0 > do_wp_page at mm/memory.c:2798 > __handle_mm_fault+0xcb0/0xd00 > handle_pte_fault at mm/memory.c:4049 > (inlined by) __handle_mm_fault at mm/memory.c:4163 > handle_mm_fault+0xfc/0x2f0 > handle_mm_fault at mm/memory.c:4200 > do_page_fault+0x263/0x6f9 > do_user_addr_fault at arch/x86/mm/fault.c:1465 > (inlined by) do_page_fault at arch/x86/mm/fault.c:1539 > page_fault+0x34/0x40 > > read to 0xfffffc0d48ec1a00 of 8 bytes by task 94817 on cpu 69: > put_page+0x15a/0x1f0 > page_zonenum at include/linux/mm.h:923 > (inlined by) is_zone_device_page at include/linux/mm.h:929 > (inlined by) page_is_devmap_managed at include/linux/mm.h:948 > (inlined by) put_page at include/linux/mm.h:1023 > wp_page_copy+0x571/0x930 > wp_page_copy at mm/memory.c:2615 > do_wp_page+0x107/0x7b0 > __handle_mm_fault+0xcb0/0xd00 > handle_mm_fault+0xfc/0x2f0 > do_page_fault+0x263/0x6f9 > page_fault+0x34/0x40 > > Reported by Kernel Concurrency Sanitizer on: > CPU: 69 PID: 94817 Comm: systemd-udevd Tainted: G W O L 5.5.0-next-20200204+ #6 > Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019 > > A page never changes its zone number. The zone number happens to be > stored in the same word as other bits which are modified, but the zone > number bits will never be modified by any other write, so it can accept > a reload of the zone bits after an intervening write and it don't need > to use READ_ONCE(). Thus, annotate this data race using > ASSERT_EXCLUSIVE_BITS() to also assert that there are no concurrent > writes to it. > > Suggested-by: Marco Elver > Signed-off-by: Qian Cai > --- > > v2: use ASSERT_EXCLUSIVE_BITS(). > > BTW, not sure if it is easier for Andrew with Paul to pick this up (with > Andrew's ACK), since ASSERT_EXCLUSIVE_BITS() is in -rcu tree only (or likely > tomorrow's -next tree). Here are the options I know of, any of which work for me: 1. I take the patch given appropriate acks/reviews. 2. Someone hangs onto the patch until the KCSAN infrastructure hits mainline and then sends it up via whatever path. 3. One way to do #2 is to merge the -rcu tree's "kcsan" branch and then queue this patch on top of that, again sending this patch along once KCSAN hits mainline. Unusually for the -rcu tree, the "kcsan" branch is not supposed to be rebased. Either way, just let me know! Thanx, Paul > include/linux/mm.h | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 52269e56c514..0d70fafd055c 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -920,6 +920,7 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct mem_cgroup *memcg, > > static inline enum zone_type page_zonenum(const struct page *page) > { > + ASSERT_EXCLUSIVE_BITS(page->flags, ZONES_MASK << ZONES_PGSHIFT); > return (page->flags >> ZONES_PGSHIFT) & ZONES_MASK; > } > > -- > 1.8.3.1 >