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=-7.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 D7C6CC433DF for ; Thu, 13 Aug 2020 11:41:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A380320771 for ; Thu, 13 Aug 2020 11:41:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A380320771 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 335036B000D; Thu, 13 Aug 2020 07:41:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2E6966B000E; Thu, 13 Aug 2020 07:41:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1FD896B0010; Thu, 13 Aug 2020 07:41:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0200.hostedemail.com [216.40.44.200]) by kanga.kvack.org (Postfix) with ESMTP id 06BF96B000D for ; Thu, 13 Aug 2020 07:41:13 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B6863180AD802 for ; Thu, 13 Aug 2020 11:41:12 +0000 (UTC) X-FDA: 77145354384.08.comb54_4c1317c26ff3 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin08.hostedemail.com (Postfix) with ESMTP id 8E75F1819E624 for ; Thu, 13 Aug 2020 11:41:12 +0000 (UTC) X-HE-Tag: comb54_4c1317c26ff3 X-Filterd-Recvd-Size: 2521 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf18.hostedemail.com (Postfix) with ESMTP for ; Thu, 13 Aug 2020 11:41:12 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 2ED8EB750; Thu, 13 Aug 2020 11:41:33 +0000 (UTC) Date: Thu, 13 Aug 2020 13:41:05 +0200 From: Michal Hocko To: Charan Teja Reddy Cc: akpm@linux-foundation.org, vbabka@suse.cz, david@redhat.com, rientjes@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, vinmenon@codeaurora.org Subject: Re: [PATCH V2] mm, page_alloc: fix core hung in free_pcppages_bulk() Message-ID: <20200813114105.GI9477@dhcp22.suse.cz> References: <1597150703-19003-1-git-send-email-charante@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1597150703-19003-1-git-send-email-charante@codeaurora.org> X-Rspamd-Queue-Id: 8E75F1819E624 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 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 Tue 11-08-20 18:28:23, Charan Teja Reddy wrote: [...] > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index e4896e6..839039f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1304,6 +1304,11 @@ static void free_pcppages_bulk(struct zone *zone, int count, > struct page *page, *tmp; > LIST_HEAD(head); > > + /* > + * Ensure proper count is passed which otherwise would stuck in the > + * below while (list_empty(list)) loop. > + */ > + count = min(pcp->count, count); > while (count) { > struct list_head *list; How does this prevent the race actually? Don't we need something like the following instead? diff --git a/mm/page_alloc.c b/mm/page_alloc.c index e028b87ce294..45bcc7ba37c4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1317,9 +1317,16 @@ static void free_pcppages_bulk(struct zone *zone, int count, * lists */ do { + bool looped = false; + batch_free++; - if (++migratetype == MIGRATE_PCPTYPES) + if (++migratetype == MIGRATE_PCPTYPES) { + if (looped) + goto free; + migratetype = 0; + looped = true; + } list = &pcp->lists[migratetype]; } while (list_empty(list)); @@ -1352,6 +1359,7 @@ static void free_pcppages_bulk(struct zone *zone, int count, } while (--count && --batch_free && !list_empty(list)); } +free: spin_lock(&zone->lock); isolated_pageblocks = has_isolate_pageblock(zone); -- Michal Hocko SUSE Labs