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=-9.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 1F529C35240 for ; Thu, 30 Jan 2020 14:57:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E8B91206F0 for ; Thu, 30 Jan 2020 14:57:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lca.pw header.i=@lca.pw header.b="gPH3wrPi" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727298AbgA3O5H (ORCPT ); Thu, 30 Jan 2020 09:57:07 -0500 Received: from mail-qt1-f195.google.com ([209.85.160.195]:37518 "EHLO mail-qt1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727132AbgA3O5G (ORCPT ); Thu, 30 Jan 2020 09:57:06 -0500 Received: by mail-qt1-f195.google.com with SMTP id w47so2671431qtk.4 for ; Thu, 30 Jan 2020 06:57:06 -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:mime-version :content-transfer-encoding; bh=ZNin1fkHvBE9eW3g8NlOf6UaO9vwNWq4JoMAU8rk968=; b=gPH3wrPiBhJ1X1dzwiOUlqSDcnz9fUG8KhH5CL2Tov+tnlNFQiCFr0vsZvf4DrD4ql 5vMSK2C6bUevX0L/2uJd3Papwp/y4DNkymkscVJl+1U0dxB/2YsCgl5m9DdhYvTtPAFz LzAKkp0XTgLvew6SAzlQluIq6qj4PcN4wLMTKqArt7aZzH34dxWJ2Xta8ZD2eG32AMNM 9Spr3lPTnBQiwNMBFpAuCioOJBR6YcHPH9tcc1CFvtOpQelhp39EOH1xYelfF8aKhRa4 z80vCrL2qaqu2zfxF8o3EyPvBEbaxRihHPFlOfp/TwNcX8tKcxk+wuxNpdFCZOvq+6eg 137w== 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:mime-version :content-transfer-encoding; bh=ZNin1fkHvBE9eW3g8NlOf6UaO9vwNWq4JoMAU8rk968=; b=SPT9x1pqY/0fD1ktV/Yc38T2mEIKcgRJumyC8wM318qolP5ZWdNljkGbqbDmsZpFKu paRaJbeW0uWwiy1ksHel5NIwzZnoWhHbnQpXLxVKFU64anlZVnSHRKenCjuRNuAppaNd Yy9fbIzheNE1C5F/AvEsv+EHfa04weesMANMLuYt5N2wKfGjK4XPIhciF0DLXFpMgrrM XpxtzxiFK1ZOnp87oylhc/LvnmGK1AXgDIAPzam7VbzJ1w0Xf3w+K1hGQ06H2mpVgqeC 7KMYpWLEcSlM37y7QgySqcBVrO0EQuoeYlCRRd54SB8Rvz8qsedzThuvakJL5B3SKzGa SuXQ== X-Gm-Message-State: APjAAAVas+WIvtFpxXejGltuBMGaZeWJLTHUs25LkfKaPEjzQ4rGgbH8 sSXEj2UlxTkzqL1c8DHGt61lAw== X-Google-Smtp-Source: APXvYqx8U57433kel8PKdYA6yz39yF4h49woso5+R7mtiD7se9+X7qmo36Zm/yFzJAHbhcO2yc93/w== X-Received: by 2002:ac8:4419:: with SMTP id j25mr5229623qtn.378.1580396225480; Thu, 30 Jan 2020 06:57:05 -0800 (PST) Received: from ovpn-120-129.rdu2.redhat.com (pool-71-184-117-43.bstnma.fios.verizon.net. [71.184.117.43]) by smtp.gmail.com with ESMTPSA id y27sm3219559qta.50.2020.01.30.06.57.04 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 30 Jan 2020 06:57:04 -0800 (PST) From: Qian Cai To: akpm@linux-foundation.org Cc: dennis@kernel.org, tj@kernel.org, cl@linux.com, elver@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Qian Cai Subject: [PATCH -next] mm/util: annotate an intentional data race Date: Thu, 30 Jan 2020 09:56:49 -0500 Message-Id: <20200130145649.1240-1-cai@lca.pw> X-Mailer: git-send-email 2.21.0 (Apple Git-122.2) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "vm_committed_as.count" could be accessed concurrently as reported by KCSAN, read to 0xffffffff923164f8 of 8 bytes by task 1268 on cpu 38: __vm_enough_memory+0x43/0x280 mm/util.c:801 mmap_region+0x1b2/0xb90 mm/mmap.c:1726 do_mmap+0x45c/0x700 vm_mmap_pgoff+0xc0/0x130 vm_mmap+0x71/0x90 elf_map+0xa1/0x1b0 load_elf_binary+0x9de/0x2180 search_binary_handler+0xd8/0x2b0 __do_execve_file+0xb61/0x1080 __x64_sys_execve+0x5f/0x70 do_syscall_64+0x91/0xb47 entry_SYSCALL_64_after_hwframe+0x49/0xbe write to 0xffffffff923164f8 of 8 bytes by task 1265 on cpu 41: percpu_counter_add_batch+0x83/0xd0 lib/percpu_counter.c:91 exit_mmap+0x178/0x220 include/linux/mman.h:68 mmput+0x10e/0x270 flush_old_exec+0x572/0xfe0 load_elf_binary+0x467/0x2180 search_binary_handler+0xd8/0x2b0 __do_execve_file+0xb61/0x1080 __x64_sys_execve+0x5f/0x70 do_syscall_64+0x91/0xb47 entry_SYSCALL_64_after_hwframe+0x49/0xbe The warning is almost impossible to trigger according to the commit 82f71ae4a2b8 ("mm: catch memory commitment underflow") but leave it for now to catch any possible unbalanced vm_unacct_memory() in the future. Since only the read is operating as lockless, mark it as an intentional data race using the data_race() macro. Signed-off-by: Qian Cai --- mm/util.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/util.c b/mm/util.c index 988d11e6c17c..528d2c710771 100644 --- a/mm/util.c +++ b/mm/util.c @@ -798,8 +798,8 @@ int __vm_enough_memory(struct mm_struct *mm, long pages, int cap_sys_admin) { long allowed; - VM_WARN_ONCE(percpu_counter_read(&vm_committed_as) < - -(s64)vm_committed_as_batch * num_online_cpus(), + VM_WARN_ONCE(data_race(percpu_counter_read(&vm_committed_as) < + -(s64)vm_committed_as_batch * num_online_cpus()), "memory commitment underflow"); vm_acct_memory(pages); -- 2.21.0 (Apple Git-122.2)