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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 717A9C43381 for ; Fri, 8 Mar 2019 11:29:59 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2212820811 for ; Fri, 8 Mar 2019 11:29:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2212820811 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=i-love.sakura.ne.jp Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 8DB398E0003; Fri, 8 Mar 2019 06:29:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 861388E0002; Fri, 8 Mar 2019 06:29:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 72A558E0003; Fri, 8 Mar 2019 06:29:58 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from mail-it1-f198.google.com (mail-it1-f198.google.com [209.85.166.198]) by kanga.kvack.org (Postfix) with ESMTP id 48F288E0002 for ; Fri, 8 Mar 2019 06:29:58 -0500 (EST) Received: by mail-it1-f198.google.com with SMTP id i4so11674495itb.1 for ; Fri, 08 Mar 2019 03:29:58 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-original-authentication-results:x-gm-message-state:subject:to:cc :references:from:message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=SajXQzW9X04+yPnaZqWHEKOB0mF5f8KwT4oltqr0ZBw=; b=mCH6+dAj65avPFv7pEM/klnugvcvml3/IIcrLKOEdAjZ70SQX9TMmaG72AHRZTG2Lm pjbsAwjmtZCDvP0B1INcpQfs7hxW9bPw7VX6JR2yc0IlBDqscmafPEcPfaveLR+qASNu FoU9vvGft3N34A1CpbimtHS5B6rAJicWCqBiz8v+8NH1ylufcw7IyW20i17FVYQS/Dml EUuJXOfwyT9ATMLAnkiaaTK85saZiFHp9HqQu3L5yXm8Jnw4hjcRupUBbqXP976h17Tn QGcHYaKNcfGQYuJLbHs+R8PUElIVA50SBMP0Bl1JSR+PJV9jxocTXSJA0XGtEDcF0gec ZJ9Q== X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp X-Gm-Message-State: APjAAAXvoyZ3ZEBh17kENWVTSYSqo+TUppfJAH3Hbw58+GGRZ56W7eEa lozJCaCb0DezcZggWQ4uIM2gPjWH/CKhtnxRJqIn7xEvJeUe3QZvcDh4HLvNnVz33+DVWd8GaJn B6BDF/YWo1HgC3umMOxMQhWt0M4e3m9ShWAenz3lBZdiXaJRkJzZKvRFUt42n8J1ZvQ== X-Received: by 2002:a24:10d0:: with SMTP id 199mr7182280ity.131.1552044598059; Fri, 08 Mar 2019 03:29:58 -0800 (PST) X-Google-Smtp-Source: APXvYqw8GT9DQEnu2Tnz0O/YmJGAuxFm7Q+gbE6E05rrYvcGeABfhCXQzMImIyhy3UBf4bIkVbl7 X-Received: by 2002:a24:10d0:: with SMTP id 199mr7182248ity.131.1552044597139; Fri, 08 Mar 2019 03:29:57 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1552044597; cv=none; d=google.com; s=arc-20160816; b=D+dtFKgLgI/MZebwclcI8eA36jEhJBeyjurX8ORJCKAO7PmHVe+28gUU2t6DmLI+T+ wBhpSAGz4wfVm2+7O5GVqKUMBCwsglBhsmHvTiVRFbMscVX95iE9wgglMwHf4hTZDiet 5Jsx7rrMSone0Vki2UOwnvowaai1gaZSxphBEZ798fG8INNjxhvkj5vhIPrf+RZQqwI/ OV3kM6mvsy5XfVHu88q0f+3En9xtLcZomZbN6pgxKI7+Z2z9Ol8QvmlXr9PfEf2ubQII W0uP/b6NU/B6ZOGRN2fICXU88MSB/6MIUp7gz5iBBtaNcE1tE2oHiu7DfyzQfUFAl5N7 dziQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:content-language:in-reply-to:mime-version :user-agent:date:message-id:from:references:cc:to:subject; bh=SajXQzW9X04+yPnaZqWHEKOB0mF5f8KwT4oltqr0ZBw=; b=hY4jlTfNLuqQaOWzfgPVToglM880aX3WmWFyvppM+3vuGIj13jfkYvVCL85GzJkT1b YE9tXkdPzRCHaS302P3gaC3dvYqRBPbjApHCYupG89k6nOFTC/D4/EgA4hnhmE0NlW3a Gl+TuaRv3DI7tILnVuLNFqyZzk+BR1CwiPbWHQ+mS1YO29VodXBtjZmyE6OB9sHH0xCc 0QMndoYXbwhFOASXdkiAIQbBzwYN+UnTuHzcd07aoFOiJvMuAwIzRyp8kQq0WTUGbhTY SGnXNP4hq9FxSlZQrDxq6zGvREs2yPag8MGcBWNcMHpd49cGu/2ZCgNnVgtWA/LDssEP Eg2A== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp Received: from www262.sakura.ne.jp (www262.sakura.ne.jp. [202.181.97.72]) by mx.google.com with ESMTPS id 84si3656907jam.112.2019.03.08.03.29.56 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 08 Mar 2019 03:29:56 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) client-ip=202.181.97.72; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of penguin-kernel@i-love.sakura.ne.jp designates 202.181.97.72 as permitted sender) smtp.mailfrom=penguin-kernel@i-love.sakura.ne.jp Received: from fsav401.sakura.ne.jp (fsav401.sakura.ne.jp [133.242.250.100]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id x28BTplf050362; Fri, 8 Mar 2019 20:29:51 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav401.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav401.sakura.ne.jp); Fri, 08 Mar 2019 20:29:51 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav401.sakura.ne.jp) Received: from [192.168.1.8] (softbank126126163036.bbtec.net [126.126.163.36]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id x28BTjFe050310 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NO); Fri, 8 Mar 2019 20:29:51 +0900 (JST) (envelope-from penguin-kernel@i-love.sakura.ne.jp) Subject: Re: [PATCH] mm,oom: Teach lockdep about oom_lock. To: Michal Hocko Cc: akpm@linux-foundation.org, linux-mm@kvack.org References: <1552040522-9085-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> <20190308110325.GF5232@dhcp22.suse.cz> From: Tetsuo Handa Message-ID: <0ada8109-19a7-6d9c-8420-45f32811c6aa@i-love.sakura.ne.jp> Date: Fri, 8 Mar 2019 20:29:46 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <20190308110325.GF5232@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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: On 2019/03/08 20:03, Michal Hocko wrote: > On Fri 08-03-19 19:22:02, Tetsuo Handa wrote: >> Since we are not allowed to depend on blocking memory allocations when >> oom_lock is already held, teach lockdep to consider that blocking memory >> allocations might wait for oom_lock at as early location as possible, and >> teach lockdep to consider that oom_lock is held by mutex_lock() than by >> mutex_trylock(). > > I do not understand this. It is quite likely that we will have multiple > allocations hitting this path while somebody else might hold the oom > lock. The thread who succeeded to hold oom_lock must not involve blocking memory allocations. It is explained in the comment before get_page_from_freelist(). > > What kind of problem does this actually want to prevent? Could you be > more specific please? e.g. --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3688,6 +3688,7 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t *nodemask, const char *fmt, ...) * attempt shall not depend on __GFP_DIRECT_RECLAIM && !__GFP_NORETRY * allocation which will never fail due to oom_lock already held. */ + kfree(kmalloc(PAGE_SIZE, GFP_NOIO)); page = get_page_from_freelist((gfp_mask | __GFP_HARDWALL) & ~__GFP_DIRECT_RECLAIM, order, ALLOC_WMARK_HIGH|ALLOC_CPUSET, ac); Since https://lore.kernel.org/lkml/20190308013134.GB4063@jagdpanzerIV/T/#u made me worry that we might by error introduce such dependency in near future, I propose this change as a proactive protection.