From patchwork Fri Aug 14 03:00:14 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Andrew Morton X-Patchwork-Id: 266554 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,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 E79C7C433DF for ; Fri, 14 Aug 2020 03:00:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5B9D20716 for ; Fri, 14 Aug 2020 03:00:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597374016; bh=egEDfFWEsu8u2ioZb3d3d9OXAZsoL+GxKHwv/9cwC+Q=; h=Date:From:To:Subject:In-Reply-To:List-ID:From; b=IAqGuWezmS7OyCzNC/57DF/8tFa63EkiCwogy9Bzl9mtrgn4AwVzxCeZJ6bMb604t ZOgV60rQKsJaLMa51Ko/O6X1pkbA/mT2csR11AgLu9P+D5W08GEZxtsAv3E5zKn9oT 7Hw5doNx3hB8+J4xTrsurEQcQCANAXcNPiS9wiJU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726564AbgHNDAQ (ORCPT ); Thu, 13 Aug 2020 23:00:16 -0400 Received: from mail.kernel.org ([198.145.29.99]:38648 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726567AbgHNDAP (ORCPT ); Thu, 13 Aug 2020 23:00:15 -0400 Received: from localhost.localdomain (c-73-231-172-41.hsd1.ca.comcast.net [73.231.172.41]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id C07AC2078B; Fri, 14 Aug 2020 03:00:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597374015; bh=egEDfFWEsu8u2ioZb3d3d9OXAZsoL+GxKHwv/9cwC+Q=; h=Date:From:To:Subject:In-Reply-To:From; b=lP/NWdO/1n7E+7QOlzd7kpMCZTQaQ8a7Dw/+BjRSmFI0AChD7jPmmEVKrKv5jTPvM keU5T3zkrXbExU9+GjvIKvCAMUMQiXWJJ7+A+YMurhgsMXh/hPm+bbILv+QasgOKDi U28WDNBJKWqy4BIs7nV8UQ4HqjL3r7tGST8K4VCY= Date: Thu, 13 Aug 2020 20:00:14 -0700 From: Andrew Morton To: charante@codeaurora.org, david@redhat.com, mhocko@suse.com, mm-commits@vger.kernel.org, rientjes@google.com, stable@vger.kernel.org, vbabka@suse.cz, vinmenon@codeaurora.org Subject: + mm-page_alloc-fix-core-hung-in-free_pcppages_bulk.patch added to -mm tree Message-ID: <20200814030014.ODl4NLbRv%akpm@linux-foundation.org> In-Reply-To: <20200811182949.e12ae9a472e3b5e27e16ad6c@linux-foundation.org> User-Agent: s-nail v14.8.16 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org The patch titled Subject: mm, page_alloc: fix core hung in free_pcppages_bulk() has been added to the -mm tree. Its filename is mm-page_alloc-fix-core-hung-in-free_pcppages_bulk.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-fix-core-hung-in-free_pcppages_bulk.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-fix-core-hung-in-free_pcppages_bulk.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Charan Teja Reddy Subject: mm, page_alloc: fix core hung in free_pcppages_bulk() The following race is observed with the repeated online, offline and a delay between two successive online of memory blocks of movable zone. P1 P2 Online the first memory block in the movable zone. The pcp struct values are initialized to default values,i.e., pcp->high = 0 & pcp->batch = 1. Allocate the pages from the movable zone. Try to Online the second memory block in the movable zone thus it entered the online_pages() but yet to call zone_pcp_update(). This process is entered into the exit path thus it tries to release the order-0 pages to pcp lists through free_unref_page_commit(). As pcp->high = 0, pcp->count = 1 proceed to call the function free_pcppages_bulk(). Update the pcp values thus the new pcp values are like, say, pcp->high = 378, pcp->batch = 63. Read the pcp's batch value using READ_ONCE() and pass the same to free_pcppages_bulk(), pcp values passed here are, batch = 63, count = 1. Since num of pages in the pcp lists are less than ->batch, then it will stuck in while(list_empty(list)) loop with interrupts disabled thus a core hung. Avoid this by ensuring free_pcppages_bulk() is called with proper count of pcp list pages. The mentioned race is some what easily reproducible without [1] because pcp's are not updated for the first memory block online and thus there is a enough race window for P2 between alloc+free and pcp struct values update through onlining of second memory block. With [1], the race still exists but it is very narrow as we update the pcp struct values for the first memory block online itself. This is not limited to the movable zone, it could also happen in cases with the normal zone (e.g., hotplug to a node that only has DMA memory, or no other memory yet). [1]: https://patchwork.kernel.org/patch/11696389/ Link: http://lkml.kernel.org/r/1597150703-19003-1-git-send-email-charante@codeaurora.org Fixes: 5f8dcc21211a ("page-allocator: split per-cpu list into one-list-per-migrate-type") Signed-off-by: Charan Teja Reddy Acked-by: David Hildenbrand Acked-by: David Rientjes Cc: Michal Hocko Cc: Vlastimil Babka Cc: Vinayak Menon Cc: [2.6+] Signed-off-by: Andrew Morton --- mm/page_alloc.c | 5 +++++ 1 file changed, 5 insertions(+) --- a/mm/page_alloc.c~mm-page_alloc-fix-core-hung-in-free_pcppages_bulk +++ a/mm/page_alloc.c @@ -1301,6 +1301,11 @@ static void free_pcppages_bulk(struct zo 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;