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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 CB573C2D0DB for ; Thu, 30 Jan 2020 20:02:27 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8517020708 for ; Thu, 30 Jan 2020 20:02:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8517020708 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3B5296B0381; Thu, 30 Jan 2020 15:02:27 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 365E26B0383; Thu, 30 Jan 2020 15:02:27 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 27BCC6B0384; Thu, 30 Jan 2020 15:02:27 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0151.hostedemail.com [216.40.44.151]) by kanga.kvack.org (Postfix) with ESMTP id 10B096B0381 for ; Thu, 30 Jan 2020 15:02:27 -0500 (EST) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id A1CE38248047 for ; Thu, 30 Jan 2020 20:02:26 +0000 (UTC) X-FDA: 76435372692.13.way27_4f77b43e1771d X-HE-Tag: way27_4f77b43e1771d X-Filterd-Recvd-Size: 4497 Received: from mail-qt1-f193.google.com (mail-qt1-f193.google.com [209.85.160.193]) by imf35.hostedemail.com (Postfix) with ESMTP for ; Thu, 30 Jan 2020 20:02:25 +0000 (UTC) Received: by mail-qt1-f193.google.com with SMTP id d5so3550690qto.0 for ; Thu, 30 Jan 2020 12:02:25 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=EnO9ApUhravM+tL102IQlojS3LeUikkMXEduxs5VnRY=; b=Gt4BvT22w8uJVTSZJmrhWsJVX9m4LMHJk8/eboshHKmAFIS/FxY2/UVqs+R5VlMqbY HPXjrTk7s2nZdkbylDvyWtiNOB6VbJ9uTvomuIMd5XxN29nWXOzXi0Ix+Gmnl5KEJ4+5 Cb3Do9kG8NGTwt8zBgFMh34yDksRmIrZ7PGkrZGyvsE78IFgbDLuH/eNo9CYlfPh7y2m 0nQb7mwV0enFSowy9LhV7iiQsp9SrSGtxlTy5Jw08jdwQIbkQcIlBmIFkvuNEV1X+kIe IiY642XiaLJs/TRhCh+spQg/eeHCwMLxw7gbECavibLGHfPokuOHP6kEDcS0c1jstvwb 0FZg== X-Gm-Message-State: APjAAAVEDC9x2Tds2BKzpNtY4WdqsDdfby9X2aEWgOQ9Q5+1+JwjXZow YqlFAwLJrdyOa8kHNSzKamQ= X-Google-Smtp-Source: APXvYqzTd0jiVB0C/NGRDY2nITRBPLL+esJyO9jJ6SAdUEND2P7U5Z3tpNG7u1P+TegikMJjbZH6YA== X-Received: by 2002:ac8:6910:: with SMTP id e16mr6828095qtr.273.1580414545491; Thu, 30 Jan 2020 12:02:25 -0800 (PST) Received: from dennisz-mbp ([2620:10d:c091:480::308e]) by smtp.gmail.com with ESMTPSA id f4sm3311771qka.89.2020.01.30.12.02.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Jan 2020 12:02:24 -0800 (PST) Date: Thu, 30 Jan 2020 20:01:50 +0000 From: Dennis Zhou To: Qian Cai Cc: akpm@linux-foundation.org, dennis@kernel.org, tj@kernel.org, cl@linux.com, elver@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -next] mm/util: annotate an intentional data race Message-ID: <20200130200150.GA99121@dennisz-mbp> References: <20200130145649.1240-1-cai@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200130145649.1240-1-cai@lca.pw> User-Agent: Mutt/1.12.2 (2019-09-21) X-Bogosity: Ham, tests=bogofilter, spamicity=0.007318, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Jan 30, 2020 at 09:56:49AM -0500, Qian Cai wrote: > "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) > Acked-by: Dennis Zhou Thanks, Dennis