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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 962ACC433F5 for ; Tue, 9 Nov 2021 00:53:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 1B98B611BF for ; Tue, 9 Nov 2021 00:53:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 1B98B611BF Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 3CB986B0071; Mon, 8 Nov 2021 19:53:36 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 37B106B0072; Mon, 8 Nov 2021 19:53:36 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 21B126B0073; Mon, 8 Nov 2021 19:53:36 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0027.hostedemail.com [216.40.44.27]) by kanga.kvack.org (Postfix) with ESMTP id 0FC3A6B0071 for ; Mon, 8 Nov 2021 19:53:36 -0500 (EST) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id B04481839C9A2 for ; Tue, 9 Nov 2021 00:53:35 +0000 (UTC) X-FDA: 78787568790.18.E0D4F63 Received: from out1.migadu.com (out1.migadu.com [91.121.223.63]) by imf07.hostedemail.com (Postfix) with ESMTP id F3FD210004F4 for ; Tue, 9 Nov 2021 00:53:34 +0000 (UTC) Date: Tue, 9 Nov 2021 09:53:20 +0900 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1636419212; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Ly//+PLTq734fEL3QzvD6IFnidowZVyd7f7YneJBS20=; b=lxKivXwjJZttf+pbMJfogNfjs5aOszEpK+y8WNKYHLvkaGleVM9DVBKUh6ZtPxQC4Zayw+ 0QkQaCF6kNoME6tFRTge2IK6AenITTJKIDfqRk65PZKZKV1Mpe21/rnePN6G7oaxbrQVzZ FpZsnkDH1jYY50Zh5ZVLq9NyF6UpmEY= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Naoya Horiguchi To: Yang Shi Cc: Linux MM , Andrew Morton , David Hildenbrand , Oscar Salvador , Michal Hocko , Ding Hui , Tony Luck , "Aneesh Kumar K.V" , Miaohe Lin , Peter Xu , Naoya Horiguchi , Linux Kernel Mailing List Subject: Re: [PATCH v3 3/3] mm/hwpoison: fix unpoison_memory() Message-ID: <20211109005320.GA3341842@u2004> References: <20211105055058.3152564-1-naoya.horiguchi@linux.dev> <20211105055058.3152564-4-naoya.horiguchi@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: naoya.horiguchi@linux.dev Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=linux.dev header.s=key1 header.b=lxKivXwj; spf=pass (imf07.hostedemail.com: domain of naoya.horiguchi@linux.dev designates 91.121.223.63 as permitted sender) smtp.mailfrom=naoya.horiguchi@linux.dev; dmarc=pass (policy=none) header.from=linux.dev X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: F3FD210004F4 X-Stat-Signature: 9mu67zrfpooundfotras3p7zd4jbb9ra X-HE-Tag: 1636419214-621666 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 Mon, Nov 08, 2021 at 03:27:55PM -0800, Yang Shi wrote: > On Thu, Nov 4, 2021 at 10:52 PM Naoya Horiguchi > wrote: ... > > @@ -1942,6 +1987,26 @@ core_initcall(memory_failure_init); > > pr_info(fmt, pfn); \ > > }) > > > > +static inline int clear_page_hwpoison(struct ratelimit_state *rs, struct page *p) > > +{ > > + if (TestClearPageHWPoison(p)) { > > + unpoison_pr_info("Unpoison: Software-unpoisoned page %#lx\n", > > + page_to_pfn(p), rs); > > + num_poisoned_pages_dec(); > > + return 1; > > + } > > + return 0; > > +} > > + > > +static inline int unpoison_taken_off_page(struct ratelimit_state *rs, > > + struct page *p) > > +{ > > + if (put_page_back_buddy(p) && clear_page_hwpoison(rs, p)) > > It seems there might be race condition between free and allocation to > kick the page out of buddy before the hwpoisoned flag is cleared IIUC? > > CPU A CPU B > Free: Allocation: > acquire zone lock > put back to buddy > release zone lock > acquire zone lock > try to allocate this page > if it is hwpoisoned then reset > PageBuddy (not buddy page anymore) > release zone lock > > Did I miss something? No, this is a nice catch. CPU B finds hwpoisoned page on free list then calling bad_page(). So doing "put back to buddy" and clear_page_hwpoison inside a single zone lock should prevent this race. Thanks, Naoya Horiguchi