From patchwork Mon Oct 25 07:00:15 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yuanzheng Song X-Patchwork-Id: 12580789 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 46E04C433FE for ; Mon, 25 Oct 2021 06:45:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id BDB1F60F46 for ; Mon, 25 Oct 2021 06:45:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org BDB1F60F46 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 554746B006C; Mon, 25 Oct 2021 02:45:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 504A46B0072; Mon, 25 Oct 2021 02:45:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3F32E940007; Mon, 25 Oct 2021 02:45:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0021.hostedemail.com [216.40.44.21]) by kanga.kvack.org (Postfix) with ESMTP id 2FBA86B006C for ; Mon, 25 Oct 2021 02:45:42 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id C50AE18116E31 for ; Mon, 25 Oct 2021 06:45:41 +0000 (UTC) X-FDA: 78734024082.14.D79E42B Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by imf07.hostedemail.com (Postfix) with ESMTP id C7F8B1000098 for ; Mon, 25 Oct 2021 06:45:40 +0000 (UTC) Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Hd55D4Kdmz1DHrQ; Mon, 25 Oct 2021 14:43:44 +0800 (CST) Received: from dggpeml500026.china.huawei.com (7.185.36.106) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Mon, 25 Oct 2021 14:45:37 +0800 Received: from localhost.localdomain (10.175.112.125) by dggpeml500026.china.huawei.com (7.185.36.106) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.15; Mon, 25 Oct 2021 14:45:36 +0800 From: Yuanzheng Song To: , , , , , Subject: [PATCH -next] mm/percpu: fix data-race with pcpu_nr_empty_pop_pages Date: Mon, 25 Oct 2021 07:00:15 +0000 Message-ID: <20211025070015.553813-1-songyuanzheng@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.175.112.125] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500026.china.huawei.com (7.185.36.106) X-CFilter-Loop: Reflected X-Stat-Signature: spq4pzyhdd9n7yodqoptaucthi4g3g1a Authentication-Results: imf07.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=huawei.com; spf=pass (imf07.hostedemail.com: domain of songyuanzheng@huawei.com designates 45.249.212.255 as permitted sender) smtp.mailfrom=songyuanzheng@huawei.com X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C7F8B1000098 X-HE-Tag: 1635144340-512735 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000001, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: When reading the pcpu_nr_empty_pop_pages in pcpu_alloc() and writing the pcpu_nr_empty_pop_pages in pcpu_update_empty_pages() at the same time, the data-race occurs. =========== read-write to 0xffffffff882fdd4c of 4 bytes by task 9424 on cpu 0: pcpu_update_empty_pages pcpu_chunk_populated pcpu_balance_populated pcpu_balance_workfn process_one_work worker_thread kthread ret_from_fork read to 0xffffffff882fdd4c of 4 bytes by task 9386 on cpu 3: pcpu_alloc __alloc_percpu_gfp fib_nh_common_init fib_nh_init fib_create_info fib_table_insert fib_magic ...... sock_sendmsg_nosec sock_sendmsg __sys_sendto __do_sys_sendto __se_sys_sendto __x64_sys_sendto do_syscall_64 entry_SYSCALL_64_after_hwframe ============ The same problem will occur in these functions: pcpu_reclaim_populated(), pcpu_update_empty_pages(), pcpu_isolate_chunk(). To fix this issue, use READ_ONCE() and WRITE_ONCE() to read and write the pcpu_nr_empty_pop_pages. Signed-off-by: Yuanzheng Song --- mm/percpu.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index 293009cc03ef..e8ef92e698ab 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -574,7 +574,9 @@ static void pcpu_isolate_chunk(struct pcpu_chunk *chunk) if (!chunk->isolated) { chunk->isolated = true; - pcpu_nr_empty_pop_pages -= chunk->nr_empty_pop_pages; + WRITE_ONCE(pcpu_nr_empty_pop_pages, + READ_ONCE(pcpu_nr_empty_pop_pages) - + chunk->nr_empty_pop_pages); } list_move(&chunk->list, &pcpu_chunk_lists[pcpu_to_depopulate_slot]); } @@ -585,7 +587,9 @@ static void pcpu_reintegrate_chunk(struct pcpu_chunk *chunk) if (chunk->isolated) { chunk->isolated = false; - pcpu_nr_empty_pop_pages += chunk->nr_empty_pop_pages; + WRITE_ONCE(pcpu_nr_empty_pop_pages, + READ_ONCE(pcpu_nr_empty_pop_pages) + + chunk->nr_empty_pop_pages); pcpu_chunk_relocate(chunk, -1); } } @@ -603,7 +607,8 @@ static inline void pcpu_update_empty_pages(struct pcpu_chunk *chunk, int nr) { chunk->nr_empty_pop_pages += nr; if (chunk != pcpu_reserved_chunk && !chunk->isolated) - pcpu_nr_empty_pop_pages += nr; + WRITE_ONCE(pcpu_nr_empty_pop_pages, + READ_ONCE(pcpu_nr_empty_pop_pages) + nr); } /* @@ -1874,7 +1879,7 @@ static void __percpu *pcpu_alloc(size_t size, size_t align, bool reserved, mutex_unlock(&pcpu_alloc_mutex); } - if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_LOW) + if (READ_ONCE(pcpu_nr_empty_pop_pages) < PCPU_EMPTY_POP_PAGES_LOW) pcpu_schedule_balance_work(); /* clear the areas and return address relative to base address */ @@ -2062,7 +2067,7 @@ static void pcpu_balance_populated(void) pcpu_atomic_alloc_failed = false; } else { nr_to_pop = clamp(PCPU_EMPTY_POP_PAGES_HIGH - - pcpu_nr_empty_pop_pages, + READ_ONCE(pcpu_nr_empty_pop_pages), 0, PCPU_EMPTY_POP_PAGES_HIGH); } @@ -2163,7 +2168,8 @@ static void pcpu_reclaim_populated(void) break; /* reintegrate chunk to prevent atomic alloc failures */ - if (pcpu_nr_empty_pop_pages < PCPU_EMPTY_POP_PAGES_HIGH) { + if (READ_ONCE(pcpu_nr_empty_pop_pages) < + PCPU_EMPTY_POP_PAGES_HIGH) { reintegrate = true; goto end_chunk; }