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Tue, 28 May 2024 16:42:05 +0800 Subject: Re: [linus:master] [mm] d99e3140a4: BUG:KCSAN:data-race_in_folio_remove_rmap_ptes/print_report To: David Hildenbrand , kernel test robot , Matthew Wilcox CC: , , , Andrew Morton , Vlastimil Babka , Luis Chamberlain , Muchun Song , Oscar Salvador , , References: <202405281431.c46a3be9-lkp@intel.com> <8aba80ed-7b3e-4c8c-99e8-d8a2e0b112fc@redhat.com> From: Miaohe Lin Message-ID: <4b0d996a-7499-6fce-ee19-3357f8d323cd@huawei.com> Date: Tue, 28 May 2024 16:42:05 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <8aba80ed-7b3e-4c8c-99e8-d8a2e0b112fc@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 8bit X-Originating-IP: [10.173.135.154] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To canpemm500002.china.huawei.com (7.192.104.244) X-Rspamd-Queue-Id: 2652AC0004 X-Stat-Signature: x6wii64t7boz3r5b3awt88onu5pom1q6 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1716885729-977211 X-HE-Meta: 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 JDVZdUkA G1FvsYy7PXnt1eeYgpwfB0y86zKegrBCdLGxSuU6kEZ2xT+C0GY1wTz7lQM01YrELhfAMdpFBsFXRHPcq2r3ZOlcVTemP6Q6SIN5PPgqgHguKOkUbgSV7iSx+tUsmxYh0/pJ2dqtNrOEGaZH0sr9dR50lYkEBwf9NN8sDWQybZhXgEVCeusttBZp7B6Kijx4K6zI8/YfxsoSRAVPPKatJ88Vdq4sLXO6JZ7+w4BP5seRrItiQKkO67FBqF+grrURT0UQAweiqwL0WlZFqzCbZO7eQixbH8e7Ky2oIsvQbs/cLTB/D4sjzvq1cyGCAG9/6RUfCutH+WVGd1SuVMHnv22f9Mw== 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: List-Subscribe: List-Unsubscribe: On 2024/5/28 15:43, David Hildenbrand wrote: > Am 28.05.24 um 09:11 schrieb kernel test robot: >> >> >> Hello, >> >> kernel test robot noticed "BUG:KCSAN:data-race_in_folio_remove_rmap_ptes/print_report" on: >> >> commit: d99e3140a4d33e26066183ff727d8f02f56bec64 ("mm: turn folio_test_hugetlb into a PageType") >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master >> >> [test failed on linus/master      c760b3725e52403dc1b28644fb09c47a83cacea6] >> [test failed on linux-next/master 3689b0ef08b70e4e03b82ebd37730a03a672853a] >> >> in testcase: trinity >> version: trinity-i386-abe9de86-1_20230429 >> with following parameters: >> >>     runtime: 300s >>     group: group-04 >>     nr_groups: 5 >> >> >> >> compiler: gcc-13 >> test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G >> >> (please refer to attached dmesg/kmsg for entire log/backtrace) >> >> >> we noticed this issue does not always happen. we also noticed there are >> different random KCSAN issues for both this commit and its parent. but below >> 4 only happen on this commit with not small rate and keep clean on parent. >> > > Likely that's just a page_type check racing against concurrent > mapcount changes. > > In __folio_rmap_sanity_checks() we check >     VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio); > > To make sure we don't get hugetlb folios in the wrong rmap code path. That > can easily race with concurrent mapcount changes, just like any other > page_type checks that end up in folio_test_type/page_has_type e.g., from > PFN walkers. > > Load tearing in these functions shouldn't really result in false positives > (what we care about), but READ_ONCE shouldn't hurt or make a difference. > > > From b03dc9bf27571442d886d8da624a4e4f737433f2 Mon Sep 17 00:00:00 2001 > From: David Hildenbrand > Date: Tue, 28 May 2024 09:37:20 +0200 > Subject: [PATCH] mm: read page_type using READ_ONCE > > KCSAN complains about possible data races: while we check for a > page_type -- for example for sanity checks -- we might concurrently > modify the mapcount that overlays page_type. > > Let's use READ_ONCE to avoid laod tearing (shouldn't make a difference) > and to make KCSAN happy. > > Note: nothing should really be broken besides wrong KCSAN complaints. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202405281431.c46a3be9-lkp@intel.com > Signed-off-by: David Hildenbrand LGTM. Thanks for fixing. Reviewed-by: Miaohe Lin Thanks. .