From patchwork Tue Feb 25 16:55:26 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qian Cai X-Patchwork-Id: 11404243 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id D98941395 for ; Tue, 25 Feb 2020 16:55:38 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9383C21744 for ; Tue, 25 Feb 2020 16:55:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="P184IGeA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9383C21744 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lca.pw Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id B74976B0006; Tue, 25 Feb 2020 11:55:37 -0500 (EST) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id AFE8F6B0007; Tue, 25 Feb 2020 11:55:37 -0500 (EST) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9C5A06B0008; Tue, 25 Feb 2020 11:55:37 -0500 (EST) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0178.hostedemail.com [216.40.44.178]) by kanga.kvack.org (Postfix) with ESMTP id 81C356B0006 for ; Tue, 25 Feb 2020 11:55:37 -0500 (EST) Received: from smtpin20.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 3CCCE180AD801 for ; Tue, 25 Feb 2020 16:55:37 +0000 (UTC) X-FDA: 76529250714.20.knot74_6b2e74c450863 X-Spam-Summary: 2,0,0,864be2b52cb6298b,d41d8cd98f00b204,cai@lca.pw,,RULES_HIT:41:355:379:541:800:960:973:988:989:1260:1345:1437:1535:1542:1711:1730:1747:1777:1792:2198:2199:2393:2559:2562:2731:2897:2918:3138:3139:3140:3141:3142:3353:3865:3866:3867:3868:3870:4321:5007:6261:6653:7903:10004:11026:11473:11658:11914:12043:12114:12296:12297:12438:12517:12519:12555:12679:12895:12986:13870:14018:14096:14104:14181:14394:14721:21080:21324:21444:21451:21627:21990:30012:30054,0,RBL:209.85.160.193:@lca.pw:.lbl8.mailshell.net-62.14.0.100 66.201.201.201,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fp,MSBL:0,DNSBL:neutral,Custom_rules:0:0:0,LFtime:28,LUA_SUMMARY:none X-HE-Tag: knot74_6b2e74c450863 X-Filterd-Recvd-Size: 5416 Received: from mail-qt1-f193.google.com (mail-qt1-f193.google.com [209.85.160.193]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Tue, 25 Feb 2020 16:55:36 +0000 (UTC) Received: by mail-qt1-f193.google.com with SMTP id l16so144646qtq.1 for ; Tue, 25 Feb 2020 08:55:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=lca.pw; s=google; h=from:to:cc:subject:date:message-id; bh=eI480rA4BDfxWyGgJwW8aPuYxCTO0HnuLE75vGul/Xs=; b=P184IGeAqAXRM6R0OEhOJISQRtMWwb9pZ+9c1oAjp2YYR6Dp+uD6ARuWbBtHGOZr2J vK6M4D6AzZC47x9J9h3G0MuW3tXDh+CWptXiLd+VP81+pxlCGywMqrhqyhm9rPX9LImG mNZaRu+T1/sHzEsctNZT4TQZ34JL0gnGDh60xKlsJpFyfyvfVU1n/MqSHFQdDVCOV8lc UNFv8f7ymvtvvvb101XFzxusbA2Oed3oEMx+3QjgkoJJeL5yyx7fpX6DCmCoYicsBAEK IEjLhNX56qFDHYUOi43NZuecSd1k0uDwfEaebDtDS06hVuWSB66CVTtRZhS/44GYjC9u /FcQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=eI480rA4BDfxWyGgJwW8aPuYxCTO0HnuLE75vGul/Xs=; b=T5YY4VQO9LcZC/NtgOb1Qp+rPr8X8LoppiRPAN4eHy9XC9WAJPH4s97riM4ihSH5M9 XxOO8vM1pFULDpWNY+2yFF7ugaEnXj7HuB/vIW162rP2nXHBBNh5aOiGoPCNlo35FBCm zsuUlgl0U0qzp9nvjwCePSKO8A4J/VSGh2OaLVMovFV7aq9/s+r4HxH4DQT649j6azx0 RTK+Z0Dq5HRQvp12bHzZxLV19scEMNbT/x0smMIT4yxGrkFcM29Wc+d9jDODi0hS80ml jM/WDNXYQJ2gBFzwEhZwX6vYmmjCWlXjX/EkMRwool4nE6+yvTkYXvttyPWi4dKNsNZM LZ+g== X-Gm-Message-State: APjAAAVkcB+oIMn5f+72G/RKxPf1PBaLYY7KcVAPMejUO/kMpEurvIQM 3w4iVyWTDYnXTjgIoK3pP1whOg== X-Google-Smtp-Source: APXvYqy1XlyOCJvt2qv6r7oiMMhi6kuONC5iyE5pEOGafBPuUCN+6TpPX1LQbN0UxPaL4BYZySjpYg== X-Received: by 2002:ac8:6046:: with SMTP id k6mr56995736qtm.357.1582649735740; Tue, 25 Feb 2020 08:55:35 -0800 (PST) Received: from qcai.nay.com (nat-pool-bos-t.redhat.com. [66.187.233.206]) by smtp.gmail.com with ESMTPSA id 131sm2743238qkl.86.2020.02.25.08.55.34 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Feb 2020 08:55:35 -0800 (PST) From: Qian Cai To: akpm@linux-foundation.org Cc: elver@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH] mm/vmscan: fix data races at kswapd_classzone_idx Date: Tue, 25 Feb 2020 11:55:26 -0500 Message-Id: <1582649726-15474-1-git-send-email-cai@lca.pw> X-Mailer: git-send-email 1.8.3.1 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: pgdat->kswapd_classzone_idx could be accessed concurrently in wakeup_kswapd(). Plain writes and reads without any lock protection result in data races. Fix them by adding a pair of READ|WRITE_ONCE() as well as saving a branch (compilers might well optimize the original code in an unintentional way anyway). The data races were reported by KCSAN, BUG: KCSAN: data-race in wakeup_kswapd / wakeup_kswapd write to 0xffff9f427ffff2dc of 4 bytes by task 7454 on cpu 13: wakeup_kswapd+0xf1/0x400 wakeup_kswapd at mm/vmscan.c:3967 wake_all_kswapds+0x59/0xc0 wake_all_kswapds at mm/page_alloc.c:4241 __alloc_pages_slowpath+0xdcc/0x1290 __alloc_pages_slowpath at mm/page_alloc.c:4512 __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 1 lock held by mtest01/7454: #0: ffff9f425afe8808 (&mm->mmap_sem#2){++++}, at: do_page_fault+0x143/0x6f9 do_user_addr_fault at arch/x86/mm/fault.c:1405 (inlined by) do_page_fault at arch/x86/mm/fault.c:1539 irq event stamp: 6944085 count_memcg_event_mm+0x1a6/0x270 count_memcg_event_mm+0x119/0x270 __do_softirq+0x34c/0x57c irq_exit+0xa2/0xc0 read to 0xffff9f427ffff2dc of 4 bytes by task 7472 on cpu 38: wakeup_kswapd+0xc8/0x400 wake_all_kswapds+0x59/0xc0 __alloc_pages_slowpath+0xdcc/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 1 lock held by mtest01/7472: #0: ffff9f425a9ac148 (&mm->mmap_sem#2){++++}, at: do_page_fault+0x143/0x6f9 irq event stamp: 6793561 count_memcg_event_mm+0x1a6/0x270 count_memcg_event_mm+0x119/0x270 __do_softirq+0x34c/0x57c irq_exit+0xa2/0xc0 Signed-off-by: Qian Cai --- mm/vmscan.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) diff --git a/mm/vmscan.c b/mm/vmscan.c index 876370565455..400950734e5a 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -3961,11 +3961,10 @@ void wakeup_kswapd(struct zone *zone, gfp_t gfp_flags, int order, return; pgdat = zone->zone_pgdat; - if (pgdat->kswapd_classzone_idx == MAX_NR_ZONES) - pgdat->kswapd_classzone_idx = classzone_idx; - else - pgdat->kswapd_classzone_idx = max(pgdat->kswapd_classzone_idx, - classzone_idx); + if (READ_ONCE(pgdat->kswapd_classzone_idx) == MAX_NR_ZONES || + READ_ONCE(pgdat->kswapd_classzone_idx) < classzone_idx) + WRITE_ONCE(pgdat->kswapd_classzone_idx, classzone_idx); + pgdat->kswapd_order = max(pgdat->kswapd_order, order); if (!waitqueue_active(&pgdat->kswapd_wait)) return;