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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2E320C77B62 for ; Tue, 4 Apr 2023 01:42:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B50D66B0078; Mon, 3 Apr 2023 21:42:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AE80B6B007E; Mon, 3 Apr 2023 21:42:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7C4A16B007D; Mon, 3 Apr 2023 21:42:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 605B26B0074 for ; Mon, 3 Apr 2023 21:42:42 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 40FAEA086F for ; 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imf03.hostedemail.com; dkim=none; spf=pass (imf03.hostedemail.com: domain of yebin@huaweicloud.com designates 45.249.212.51 as permitted sender) smtp.mailfrom=yebin@huaweicloud.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1680572560; a=rsa-sha256; cv=none; b=78GnlgbXw5H/k+R2rVlpXplN8v1v7qMyRF0WLytoUT487ar4dMqI45ogbH3IaT6l9XbjJb Jzhy5SIrSQ4iLaDYKL5xe5095kk94tSKcOfjhaRYNS8T3uDa7uY+I7qpZEp078Agzv0U/l 0NqC6EuYQ0XMlZ2vgl2pAfX9+5cLABE= Received: from mail02.huawei.com (unknown [172.30.67.169]) by dggsgout11.his.huawei.com (SkyGuard) with ESMTP id 4Pr9Vw2Fzsz4f3pBZ for ; Tue, 4 Apr 2023 09:42:32 +0800 (CST) Received: from huaweicloud.com (unknown [10.175.127.227]) by APP3 (Coremail) with SMTP id _Ch0CgBH9CGHgCtkmLh6GA--.26422S6; Tue, 04 Apr 2023 09:42:33 +0800 (CST) From: Ye Bin To: dennis@kernel.org, tj@kernel.org, cl@linux.com, linux-mm@kvack.org, yury.norov@gmail.com, andriy.shevchenko@linux.intel.com, linux@rasmusvillemoes.dk Cc: linux-kernel@vger.kernel.org, dchinner@redhat.com, yebin10@huawei.com Subject: [PATCH 2/2] lib/percpu_counter: fix dying cpu compare race Date: Tue, 4 Apr 2023 09:42:06 +0800 Message-Id: <20230404014206.3752945-3-yebin@huaweicloud.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20230404014206.3752945-1-yebin@huaweicloud.com> References: <20230404014206.3752945-1-yebin@huaweicloud.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-CM-TRANSID:_Ch0CgBH9CGHgCtkmLh6GA--.26422S6 X-Coremail-Antispam: 1UD129KBjvJXoW7ZFW7ArWDXw1ktFy7KFyfZwb_yoW8WFy5pr 4UKry5Jr18AF92k343Kw1vqF9I9r1kAF4rKwnrGF1fAFnxZa45urW0yrs8JF109rn7Wrya qryjgF4xCa4Yv3JanT9S1TB71UUUUUUqnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDU0xBIdaVrnRJUUUB0b4IE77IF4wAFF20E14v26rWj6s0DM7CY07I20VC2zVCF04k2 6cxKx2IYs7xG6rWj6s0DM7CIcVAFz4kK6r1j6r18M28IrcIa0xkI8VA2jI8067AKxVWUXw A2048vs2IY020Ec7CjxVAFwI0_Gr0_Xr1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxS w2x7M28EF7xvwVC0I7IYx2IY67AKxVW7JVWDJwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxV W8Jr0_Cr1UM28EF7xvwVC2z280aVAFwI0_GcCE3s1l84ACjcxK6I8E87Iv6xkF7I0E14v2 6rxl6s0DM2AIxVAIcxkEcVAq07x20xvEncxIr21l5I8CrVACY4xI64kE6c02F40Ex7xfMc Ij6xIIjxv20xvE14v26r1j6r18McIj6I8E87Iv67AKxVWUJVW8JwAm72CE4IkC6x0Yz7v_ Jr0_Gr1lF7xvr2IYc2Ij64vIr41lFIxGxcIEc7CjxVA2Y2ka0xkIwI1l42xK82IYc2Ij64 vIr41l4I8I3I0E4IkC6x0Yz7v_Jr0_Gr1lx2IqxVAqx4xG67AKxVWUJVWUGwC20s026x8G jcxK67AKxVWUGVWUWwC2zVAF1VAY17CE14v26r1q6r43MIIYrxkI7VAKI48JMIIF0xvE2I x0cI8IcVAFwI0_Jr0_JF4lIxAIcVC0I7IYx2IY6xkF7I0E14v26r4j6F4UMIIF0xvE42xK 8VAvwI8IcIk0rVWUJVWUCwCI42IY6I8E87Iv67AKxVWUJVW8JwCI42IY6I8E87Iv6xkF7I 0E14v26r4j6r4UJbIYCTnIWIevJa73UjIFyTuYvjxU2GYLDUUUU X-CM-SenderInfo: p1hex046kxt4xhlfz01xgou0bp/ X-CFilter-Loop: Reflected X-Stat-Signature: 8mdxo84c67kuhyu8yo5399g5pmhri9ji X-Rspam-User: X-Rspamd-Queue-Id: 8A7D420019 X-Rspamd-Server: rspam06 X-HE-Tag: 1680572558-643184 X-HE-Meta: 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 x1+jQJl7 YLTxE/PCgzN4c0fZjRqEJ4+2amZkHkubl8VTTAZf085Uv5lx5RZSftH4sbCu4NEnfVyw6QGISm9hXVM7N8PFGTEhYorHy6T470lINxQsBRJyBMIcslgkAXiDqkTZaC45es7mrqFSOZeJCubvQDvs/3ihAsTE5igqxIFeEpSyUWzWspPmiMaKtPAJ3iKjhI36O6wUc2g3iXxSBQLgvBpM0204rFVAR4t72p0ZRKHK5cpp1OZCIUu6Uw3p5apN1IcfZyCcJpbFlYqTQqmN+Vqoj0wfHfNI16Xe3ubF+55XKBen1H+blUKm+9ZvwqLG6D5EvincT 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: From: Ye Bin In commit 8b57b11cca88 ("pcpcntrs: fix dying cpu summation race") a race condition between a cpu dying and percpu_counter_sum() iterating online CPUs was identified. Acctually, there's the same race condition between a cpu dying and __percpu_counter_compare(). Here, use 'num_online_cpus()' for quick judgment. But 'num_online_cpus()' will be decreased before call 'percpu_counter_cpu_dead()', then maybe return incorrect result. To solve above issue, also need to add dying CPUs count when do quick judgment in __percpu_counter_compare(). Signed-off-by: Ye Bin --- lib/percpu_counter.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c index 5004463c4f9f..399840cb0012 100644 --- a/lib/percpu_counter.c +++ b/lib/percpu_counter.c @@ -227,6 +227,15 @@ static int percpu_counter_cpu_dead(unsigned int cpu) return 0; } +static __always_inline unsigned int num_count_cpus(void) +{ +#ifdef CONFIG_HOTPLUG_CPU + return (num_online_cpus() + num_dying_cpus()); +#else + return num_online_cpus(); +#endif +} + /* * Compare counter against given value. * Return 1 if greater, 0 if equal and -1 if less @@ -237,7 +246,7 @@ int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch) count = percpu_counter_read(fbc); /* Check to see if rough count will be sufficient for comparison */ - if (abs(count - rhs) > (batch * num_online_cpus())) { + if (abs(count - rhs) > (batch * num_count_cpus())) { if (count > rhs) return 1; else -- 2.31.1