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,USER_AGENT_SANE_1 autolearn=unavailable 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 64765C3F68F for ; Fri, 14 Feb 2020 16:17:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3B9B3246EB for ; Fri, 14 Feb 2020 16:17:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581697065; bh=D484hfL1Ka1ychiwgumcKtTIXt+aZrJA0ykv8bHyOPc=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:List-ID: From; b=uotbhcBBR8wwasjnkc10Xn3cGVk267ECsUgGsUzCCYpDuZ+R66H4L2kq2UEsACmn+ 2FTLCQQjrLWX8tdfta5FsOL5KSm/YUJzuDFc3kWgXmfNSKLd9D/QaICU3I0QQjcfsk wnaFppboM9cmGTnQHkM8w05Zd2lrlbr59P/q3byQ= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404547AbgBNQRo (ORCPT ); Fri, 14 Feb 2020 11:17:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:47622 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392628AbgBNQQm (ORCPT ); Fri, 14 Feb 2020 11:16:42 -0500 Received: from paulmck-ThinkPad-P72.home (unknown [193.85.242.128]) (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 CE900206D7; Fri, 14 Feb 2020 16:16:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581697002; bh=D484hfL1Ka1ychiwgumcKtTIXt+aZrJA0ykv8bHyOPc=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=L1ZVQb4vN+H8w/KqSlEO0oiUdRh4uaSM9dr6HiLNvMZN6Qu3j3wrco258SdfPIfHq 6O03JtS+nUwZkxe2mc2SLEOADy4uYeZg/OaXvjq/lO4kz0gw4ZoMZU4hOnchL+b81O eSRAfe882jqJMRc9ZpW9iOp0b8Dlzt9sTPyHkZKU= Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 6D6103520CAA; Fri, 14 Feb 2020 08:16:39 -0800 (PST) Date: Fri, 14 Feb 2020 08:16:39 -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: <20200214161639.GR2935@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <1581619089-14472-1-git-send-email-cai@lca.pw> <20200213192659.GJ2935@paulmck-ThinkPad-P72> <1581690626.7365.61.camel@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1581690626.7365.61.camel@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 Fri, Feb 14, 2020 at 09:30:26AM -0500, Qian Cai wrote: > On Thu, 2020-02-13 at 11:26 -0800, Paul E. McKenney wrote: > > 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! > > I suppose it is up to Andrew what he prefers. I may have another pile of patches > depends on some of those KCSAN things (except the data_race() macro) are coming, > so I'd like to find a way to get into -next first rather than waiting to send > them in April (once KCSAN hit the mainline) if possible. Any of the three options above would get you into -next quickly. So just let me know how you would like to proceed. 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 > > >