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=-5.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLACK autolearn=no 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 099A9C433DF for ; Sat, 15 Aug 2020 22:11:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DB83120658 for ; Sat, 15 Aug 2020 22:11:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597529493; bh=aqws28JJVcpKMu9AjldogCr+vnx1tTc5ASzbWJZLHdY=; h=Date:From:To:Subject:In-Reply-To:Reply-To:List-ID:From; b=0wj+2j496e2PEWju8eCM0sr+8381nSKwDLtLPaPHq0ocvWX0l3xju6GQzDN1FYDk0 4myvC7IABDVJ+nxDQjYJlhPOzSFhx993Y2bXgHwInZxXYMnpSKekMWiPK599J6b2qd YiJ2VreGA3oEE1PhObZuig75XLtVSUYzr6Fh39AA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728390AbgHOWLT (ORCPT ); Sat, 15 Aug 2020 18:11:19 -0400 Received: from mail.kernel.org ([198.145.29.99]:41802 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729444AbgHOWKa (ORCPT ); Sat, 15 Aug 2020 18:10:30 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (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 48A5A22D73; Sat, 15 Aug 2020 00:31:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597451511; bh=aqws28JJVcpKMu9AjldogCr+vnx1tTc5ASzbWJZLHdY=; h=Date:From:To:Subject:In-Reply-To:From; b=eYu9GZMkWxaYlYne6CO8EJ+VMT2phN3TRSzMmp2NRDY90mkxJAx6JMvG2cYgQFvFh nS2MSBqaSRfdP1SqPaAnRzMkaCI+ztloJ1bhGtWCU9MSnz5Bxj0etCvm63e6aDan2T 1RgWNC1EadiosgLhCrm8WsX8AqzwGOnVqQfo0Vr4= Date: Fri, 14 Aug 2020 17:31:50 -0700 From: Andrew Morton To: akpm@linux-foundation.org, cai@lca.pw, elver@google.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, torvalds@linux-foundation.org Subject: [patch 31/39] mm/swap.c: annotate data races for lru_rotate_pvecs Message-ID: <20200815003150.-aDiYh9vd%akpm@linux-foundation.org> In-Reply-To: <20200814172939.55d6d80b6e21e4241f1ee1f3@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: mm-commits-owner@vger.kernel.org Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Qian Cai Subject: mm/swap.c: annotate data races for lru_rotate_pvecs Read to lru_add_pvec->nr could be interrupted and then write to the same variable. The write has local interrupt disabled, but the plain reads result in data races. However, it is unlikely the compilers could do much damage here given that lru_add_pvec->nr is a "unsigned char" and there is an existing compiler barrier. Thus, annotate the reads using the data_race() macro. The data races were reported by KCSAN, BUG: KCSAN: data-race in lru_add_drain_cpu / rotate_reclaimable_page write to 0xffff9291ebcb8a40 of 1 bytes by interrupt on cpu 23: rotate_reclaimable_page+0x2df/0x490 pagevec_add at include/linux/pagevec.h:81 (inlined by) rotate_reclaimable_page at mm/swap.c:259 end_page_writeback+0x1b5/0x2b0 end_swap_bio_write+0x1d0/0x280 bio_endio+0x297/0x560 dec_pending+0x218/0x430 [dm_mod] clone_endio+0xe4/0x2c0 [dm_mod] bio_endio+0x297/0x560 blk_update_request+0x201/0x920 scsi_end_request+0x6b/0x4a0 scsi_io_completion+0xb7/0x7e0 scsi_finish_command+0x1ed/0x2a0 scsi_softirq_done+0x1c9/0x1d0 blk_done_softirq+0x181/0x1d0 __do_softirq+0xd9/0x57c irq_exit+0xa2/0xc0 do_IRQ+0x8b/0x190 ret_from_intr+0x0/0x42 delay_tsc+0x46/0x80 __const_udelay+0x3c/0x40 __udelay+0x10/0x20 kcsan_setup_watchpoint+0x202/0x3a0 __tsan_read1+0xc2/0x100 lru_add_drain_cpu+0xb8/0x3f0 lru_add_drain+0x25/0x40 shrink_active_list+0xe1/0xc80 shrink_lruvec+0x766/0xb70 shrink_node+0x2d6/0xca0 do_try_to_free_pages+0x1f7/0x9a0 try_to_free_pages+0x252/0x5b0 __alloc_pages_slowpath+0x458/0x1290 __alloc_pages_nodemask+0x3bb/0x450 alloc_pages_vma+0x8a/0x2c0 do_anonymous_page+0x16e/0x6f0 __handle_mm_fault+0xcd5/0xd40 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 read to 0xffff9291ebcb8a40 of 1 bytes by task 37761 on cpu 23: lru_add_drain_cpu+0xb8/0x3f0 lru_add_drain_cpu at mm/swap.c:602 lru_add_drain+0x25/0x40 shrink_active_list+0xe1/0xc80 shrink_lruvec+0x766/0xb70 shrink_node+0x2d6/0xca0 do_try_to_free_pages+0x1f7/0x9a0 try_to_free_pages+0x252/0x5b0 __alloc_pages_slowpath+0x458/0x1290 __alloc_pages_nodemask+0x3bb/0x450 alloc_pages_vma+0x8a/0x2c0 do_anonymous_page+0x16e/0x6f0 __handle_mm_fault+0xcd5/0xd40 handle_mm_fault+0xfc/0x2f0 do_page_fault+0x263/0x6f9 page_fault+0x34/0x40 2 locks held by oom02/37761: #0: ffff9281e5928808 (&mm->mmap_sem#2){++++}, at: do_page_fault #1: ffffffffb3ade380 (fs_reclaim){+.+.}, at: fs_reclaim_acquire.part irq event stamp: 1949217 trace_hardirqs_on_thunk+0x1a/0x1c __do_softirq+0x2e7/0x57c __do_softirq+0x34c/0x57c irq_exit+0xa2/0xc0 Reported by Kernel Concurrency Sanitizer on: CPU: 23 PID: 37761 Comm: oom02 Not tainted 5.6.0-rc3-next-20200226+ #6 Hardware name: HP ProLiant BL660c Gen9, BIOS I38 10/17/2018 Link: http://lkml.kernel.org/r/20200228044018.1263-1-cai@lca.pw Signed-off-by: Qian Cai Acked-by: Marco Elver Signed-off-by: Andrew Morton --- mm/swap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/mm/swap.c~mm-swap-annotate-data-races-for-lru_rotate_pvecs +++ a/mm/swap.c @@ -632,7 +632,8 @@ void lru_add_drain_cpu(int cpu) __pagevec_lru_add(pvec); pvec = &per_cpu(lru_rotate.pvec, cpu); - if (pagevec_count(pvec)) { + /* Disabling interrupts below acts as a compiler barrier. */ + if (data_race(pagevec_count(pvec))) { unsigned long flags; /* No harm done if a racing interrupt already did this */ @@ -793,7 +794,7 @@ void lru_add_drain_all(void) struct work_struct *work = &per_cpu(lru_add_drain_work, cpu); if (pagevec_count(&per_cpu(lru_pvecs.lru_add, cpu)) || - pagevec_count(&per_cpu(lru_rotate.pvec, cpu)) || + data_race(pagevec_count(&per_cpu(lru_rotate.pvec, cpu))) || pagevec_count(&per_cpu(lru_pvecs.lru_deactivate_file, cpu)) || pagevec_count(&per_cpu(lru_pvecs.lru_deactivate, cpu)) || pagevec_count(&per_cpu(lru_pvecs.lru_lazyfree, cpu)) || _