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 07C68C433EF for ; Wed, 2 Mar 2022 06:38:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 921C48D0002; Wed, 2 Mar 2022 01:38:55 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8D1878D0001; Wed, 2 Mar 2022 01:38:55 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7BFE08D0002; Wed, 2 Mar 2022 01:38:55 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0080.hostedemail.com [216.40.44.80]) by kanga.kvack.org (Postfix) with ESMTP id 6CA7B8D0001 for ; Wed, 2 Mar 2022 01:38:55 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 23A339F852 for ; Wed, 2 Mar 2022 06:38:55 +0000 (UTC) X-FDA: 79198493430.19.B2CD773 Received: from mail-pf1-f181.google.com (mail-pf1-f181.google.com [209.85.210.181]) by imf17.hostedemail.com (Postfix) with ESMTP id 9921840005 for ; Wed, 2 Mar 2022 06:38:54 +0000 (UTC) Received: by mail-pf1-f181.google.com with SMTP id k1so1056370pfu.2 for ; Tue, 01 Mar 2022 22:38:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=K4RKtZ4EM/v8P4fEu3jSYrerGRfgI+G2IZ0OObJQr4k=; b=j1HfZ85jE8z4taKaq8Wr1YttYtwHmHsIKldoldrrQSTsgqOxVM4cs32oAUlhIT4+qK j4TLqlA3XWATSrnLL3yV2FkNzyCj7dDJuMOHZBykJT6qR7X88qL8TjI2oaYzo+M+cAbt tfs+DYMPDwHpM4ZZY/5rNTTvyr1sFdFs+z5vXsYSq08M7KjCT+OdfKPvMVQmcXHOcQNW zMl2yWg+QNS5K8uEP/ZG357TZMisvH+aA3ZU6l7gX/VRKI0H+yVrsYUjorF5TOAQu3GE kg3MhOIDOGPciobnNiaLlYzM4tT45kpkdwdZEBi/jt3MDPUoFqFmw/Y8BFUnAv5ikHno Ln8w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to; bh=K4RKtZ4EM/v8P4fEu3jSYrerGRfgI+G2IZ0OObJQr4k=; b=0UsNXtk0mvQBl92dAKZxPPOLsykSI1EImHYs0/SA1thozm7wu8EyqwTMLB2CVvEZTm ThFBdpQ1+b+MW47tfptWve6vpWc7uZlW32oBqQ8SYGHh3upf0+DlYJWdBfvMnVYjUfPj BDMihNo/4oj/5anzpmnOxI/fPmmxA3JhwDXmSwsyz5tKkWZBEqAMPQ9CQfeL6hxKkTCJ kslNgE7SfCQJoip9KLlvVjYPyQuPZPqiaRAvOoaNFjZtVRhkmGZWOFAXsm+34GStv2/2 MpUC6d/Cno/ttMTsRrTWskHL2pVaNWqK4jnH8v6EHLSKWmpVwOJxVc7dDEj6tZ6e2rdk DTjA== X-Gm-Message-State: AOAM533kBKryAH/iL9QPiJtw7Z1A22jwLaid1JkwXOn2hdgcvDfjNxFj 7t7Zrvck4Otznn5qrsz5nQs= X-Google-Smtp-Source: ABdhPJytz+Ys8ZC903CaYKhGua+qCS/DAZYdF6uMHs4RsPDwD+SppfvEKqZUC4/0HUyiryizTgn++w== X-Received: by 2002:aa7:9f5b:0:b0:4cc:964c:99dd with SMTP id h27-20020aa79f5b000000b004cc964c99ddmr31620007pfr.42.1646203133248; Tue, 01 Mar 2022 22:38:53 -0800 (PST) Received: from localhost (2603-800c-1a02-1bae-e24f-43ff-fee6-449f.res6.spectrum.com. [2603:800c:1a02:1bae:e24f:43ff:fee6:449f]) by smtp.gmail.com with ESMTPSA id u9-20020a17090a450900b001b9b5ca299esm3886296pjg.54.2022.03.01.22.38.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Mar 2022 22:38:52 -0800 (PST) Date: Tue, 1 Mar 2022 20:38:51 -1000 From: Tejun Heo To: Sebastian Andrzej Siewior Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, Andrew Morton , Johannes Weiner , Zefan Li , Thomas Gleixner Subject: Re: [PATCH 1/2] cgroup: Use irqsave in cgroup_rstat_flush_locked(). Message-ID: References: <[PATCH0/2]CorrectlockingassumptiononPREEMPT_RT> <20220301122143.1521823-1-bigeasy@linutronix.de> <20220301122143.1521823-2-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220301122143.1521823-2-bigeasy@linutronix.de> X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9921840005 X-Stat-Signature: y81zp9c9bgazdgm6xps3foe6nzwdhd93 Authentication-Results: imf17.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=j1HfZ85j; spf=pass (imf17.hostedemail.com: domain of htejun@gmail.com designates 209.85.210.181 as permitted sender) smtp.mailfrom=htejun@gmail.com; dmarc=fail reason="SPF not aligned (relaxed), DKIM not aligned (relaxed)" header.from=kernel.org (policy=none) X-HE-Tag: 1646203134-938982 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: Hello, On Tue, Mar 01, 2022 at 01:21:42PM +0100, Sebastian Andrzej Siewior wrote: > All callers of cgroup_rstat_flush_locked() acquire cgroup_rstat_lock > either with spin_lock_irq() or spin_lock_irqsave(). > cgroup_rstat_flush_locked() itself acquires cgroup_rstat_cpu_lock which > is a raw_spin_lock. This lock is also acquired in cgroup_rstat_updated() > in IRQ context and therefore requires _irqsave() locking suffix in > cgroup_rstat_flush_locked(). > Since there is no difference between spin_lock_t and raw_spin_lock_t > on !RT lockdep does not complain here. On RT lockdep complains because > the interrupts were not disabled here and a deadlock is possible. > > Acquire the raw_spin_lock_t with disabled interrupts. > > Signed-off-by: Sebastian Andrzej Siewior Can you please add a comment explaining why irqsave is being used? As it stands, it just looks spurious. Thanks. -- tejun