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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 B8042C2D0BF for ; Mon, 16 Dec 2019 13:37:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 72938206D8 for ; Mon, 16 Dec 2019 13:37:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576503436; bh=1StiMPO8LpGHEHAabH7gzxcFrrIg+SMyk8LcOwKzZG8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=jRLkTayUWrKXXZsqzA6zrzYvztFKeqvpfxbXCOpvHw4v0+jIcUbENadKIqlySWhUh CT8gT3gluTvBdz/yzylinr/focwDH+nLynEUrbXlDzjpPVpykLyxZmcRvr8vjQsjQW ZvC+3W93awmfvNw8O4iZxddRSHjE+/I+uGytUEQ4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727956AbfLPNhP (ORCPT ); Mon, 16 Dec 2019 08:37:15 -0500 Received: from mail-wr1-f68.google.com ([209.85.221.68]:39933 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727788AbfLPNhP (ORCPT ); Mon, 16 Dec 2019 08:37:15 -0500 Received: by mail-wr1-f68.google.com with SMTP id y11so7277149wrt.6 for ; Mon, 16 Dec 2019 05:37:13 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=cqmzVJtM8/ik+wTdyhfYBEe+JzF5iuu01jawnGqmvm4=; b=tQYGGoiqAh8eGGmNFqnf1iM6QshP2ZeIsS++hg+YfTC3XN9pUVvhiGp8o7OitRXKNh CHAiNfq11s3qHi8kG3J7H/stTLuv6bTa9ojTV3KoDZ7mslUBCUwrAyV77A3fXqFEvhoU VjAzE28oqilPOOkeiJpRmorP0AwTPuWkMgb7at7Rb7NAmnEFkmYglHLYVMbYet5Ac8O9 trAmkiOkMassKcnG/xIFuC8K3NM4SGIKOgONO36Uiwo62u5OAQT/7GMUyahBruVC5bTn mCJSZ3r9jCHb4BUvGFCMbLsZ1s3Zn47h1GinzrY8gexPrSrQa7YiKcXIDwpdssRQ2QeK XcfQ== X-Gm-Message-State: APjAAAVjxRgWBAVWIrd1dVPV53ma3UcchgVYacviMrIhFnwAQ+8YL3fs /VSxJqktysuP9EJukr+Jnwg= X-Google-Smtp-Source: APXvYqw8DoZT1xy+8BNikDeso3QARwg/9LWZQz63EgJwiBZs7Ir88Njc3Qb9TIWGZJOeNYbjbrzLyA== X-Received: by 2002:adf:ee88:: with SMTP id b8mr31839416wro.249.1576503433158; Mon, 16 Dec 2019 05:37:13 -0800 (PST) Received: from localhost (prg-ext-pat.suse.com. [213.151.95.130]) by smtp.gmail.com with ESMTPSA id x132sm22762701wmg.0.2019.12.16.05.37.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Dec 2019 05:37:12 -0800 (PST) Date: Mon, 16 Dec 2019 14:37:11 +0100 From: Michal Hocko To: Davidlohr Bueso Cc: Andrew Morton , Mike Kravetz , Waiman Long , Matthew Wilcox , linux-kernel@vger.kernel.org, linux-mm@kvack.org, aneesh.kumar@linux.ibm.com Subject: Re: [PATCH v2] mm/hugetlb: defer free_huge_page() to a workqueue Message-ID: <20191216133711.GH30281@dhcp22.suse.cz> References: <20191211194615.18502-1-longman@redhat.com> <4fbc39a9-2c9c-4c2c-2b13-a548afe6083c@oracle.com> <32d2d4f2-83b9-2e40-05e2-71cd07e01b80@redhat.com> <0fcce71f-bc20-0ea3-b075-46592c8d533d@oracle.com> <20191212060650.ftqq27ftutxpc5hq@linux-p48b> <20191212063050.ufrpij6s6jkv7g7j@linux-p48b> <20191212190427.ouyohviijf5inhur@linux-p48b> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191212190427.ouyohviijf5inhur@linux-p48b> User-Agent: Mutt/1.12.2 (2019-09-21) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 12-12-19 11:04:27, Davidlohr Bueso wrote: > There have been deadlock reports[1, 2] where put_page is called > from softirq context and this causes trouble with the hugetlb_lock, > as well as potentially the subpool lock. > > For such an unlikely scenario, lets not add irq dancing overhead > to the lock+unlock operations, which could incur in expensive > instruction dependencies, particularly when considering hard-irq > safety. For example PUSHF+POPF on x86. > > Instead, just use a workqueue and do the free_huge_page() in regular > task context. I am afraid that work_struct is too large to be stuffed into the struct page array (because of the lockdep part). I think that it would be just safer to make hugetlb_lock irq safe. Are there any other locks that would require the same? -- Michal Hocko SUSE Labs