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Tue, 12 Jan 2021 01:06:22 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 10C0tcOv025629; Tue, 12 Jan 2021 01:06:21 GMT Received: from aserv0122.oracle.com (aserv0122.oracle.com [141.146.126.236]) by aserp3020.oracle.com with ESMTP id 360ke5t8fv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 12 Jan 2021 01:06:21 +0000 Received: from abhmp0013.oracle.com (abhmp0013.oracle.com [141.146.116.19]) by aserv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 10C16Hm2017380; Tue, 12 Jan 2021 01:06:17 GMT Received: from [192.168.2.112] (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Mon, 11 Jan 2021 17:06:17 -0800 Subject: Re: [PATCH v3 3/6] mm: hugetlb: fix a race between freeing and dissolving the page To: Muchun Song , akpm@linux-foundation.org Cc: n-horiguchi@ah.jp.nec.com, ak@linux.intel.com, mhocko@suse.cz, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20210110124017.86750-1-songmuchun@bytedance.com> <20210110124017.86750-4-songmuchun@bytedance.com> From: Mike Kravetz Message-ID: <5b4ccddf-d5f6-689d-5056-7ad4710792aa@oracle.com> Date: Mon, 11 Jan 2021 17:06:16 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20210110124017.86750-4-songmuchun@bytedance.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9861 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 suspectscore=0 spamscore=0 mlxlogscore=999 malwarescore=0 bulkscore=0 mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101120001 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9861 signatures=668683 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 phishscore=0 lowpriorityscore=0 bulkscore=0 priorityscore=1501 malwarescore=0 clxscore=1015 impostorscore=0 spamscore=0 mlxscore=0 suspectscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2101120001 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 1/10/21 4:40 AM, Muchun Song wrote: > There is a race condition between __free_huge_page() > and dissolve_free_huge_page(). > > CPU0: CPU1: > > // page_count(page) == 1 > put_page(page) > __free_huge_page(page) > dissolve_free_huge_page(page) > spin_lock(&hugetlb_lock) > // PageHuge(page) && !page_count(page) > update_and_free_page(page) > // page is freed to the buddy > spin_unlock(&hugetlb_lock) > spin_lock(&hugetlb_lock) > clear_page_huge_active(page) > enqueue_huge_page(page) > // It is wrong, the page is already freed > spin_unlock(&hugetlb_lock) > > The race windows is between put_page() and dissolve_free_huge_page(). > > We should make sure that the page is already on the free list > when it is dissolved. > > Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle hugepage") > Signed-off-by: Muchun Song > Cc: stable@vger.kernel.org > --- > mm/hugetlb.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) Thanks, It is unfortunate that we have to add more huge page state information to fix this issue. However, I believe we have explored all other options. Reviewed-by: Mike Kravetz -- Mike Kravetz