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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 AB45EC433F5 for ; Wed, 5 Sep 2018 22:00:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 52ADE2073D for ; Wed, 5 Sep 2018 22:00:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 52ADE2073D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727736AbeIFCcU (ORCPT ); Wed, 5 Sep 2018 22:32:20 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:59998 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727651AbeIFCcT (ORCPT ); Wed, 5 Sep 2018 22:32:19 -0400 Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id ABB8910D3; Wed, 5 Sep 2018 22:00:09 +0000 (UTC) Date: Wed, 5 Sep 2018 15:00:08 -0700 From: Andrew Morton To: Mike Kravetz Cc: Matthew Wilcox , "Aneesh Kumar K.V" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm/hugetlb: make hugetlb_lock irq safe Message-Id: <20180905150008.59d477c1f78f966a8f9c3cc8@linux-foundation.org> In-Reply-To: <78b08258-14c8-0e90-97c7-d647a11acb30@oracle.com> References: <20180905112341.21355-1-aneesh.kumar@linux.ibm.com> <20180905130440.GA3729@bombadil.infradead.org> <20180905134848.GB3729@bombadil.infradead.org> <20180905125846.eb0a9ed907b293c1b4c23c23@linux-foundation.org> <78b08258-14c8-0e90-97c7-d647a11acb30@oracle.com> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 5 Sep 2018 14:35:11 -0700 Mike Kravetz wrote: > > so perhaps we could put some > > stopgap workaround into that site and add a runtime warning into the > > put_page() code somewhere to detect puttage of huge pages from hardirq > > and softirq contexts. > > I think we would add the warning/etc at free_huge_page. The issue would > only apply to hugetlb pages, not THP. > > But, the more I think about it the more I think Aneesh's patch to do > spin_lock/unlock_irqsave is the right way to go. Currently, we only > know of one place where a put_page of hugetlb pages is done from softirq > context. So, we could take the spin_lock/unlock_bh as Matthew suggested. > When the powerpc iommu code was added, I doubt this was taken into account. > I would be afraid of someone adding put_page from hardirq context. Me too. If we're going to do this, surely we should make hugepages behave in the same fashion as PAGE_SIZE pages.