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=-9.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 6CFEBC3A5A8 for ; Wed, 4 Sep 2019 18:10:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 484EF2087E for ; Wed, 4 Sep 2019 18:10:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567620655; bh=An5nCkic9DIMAchQA8nBNy2dnhyUW1x9ls9wee2wjeA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=W6zM/vpEfIJv+cVeqZniXYScU7Lsv6fjJljLv0gEx3upeGhjzlPoBqnPJ6QBqCodU FGcua4eakxNgOe7jxOdEiO2skZec2McIBR/60Nffe4l6/ug9DX7dXmDZtme57rTN8J XR3TEiHmgMa2CXfVb8zLhltLJVoAbYXeIifMuSEk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390188AbfIDSKy (ORCPT ); Wed, 4 Sep 2019 14:10:54 -0400 Received: from mail.kernel.org ([198.145.29.99]:54664 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390170AbfIDSKw (ORCPT ); Wed, 4 Sep 2019 14:10:52 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (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 5DF1B206B8; Wed, 4 Sep 2019 18:10:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567620651; bh=An5nCkic9DIMAchQA8nBNy2dnhyUW1x9ls9wee2wjeA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dNcy2Du8an8wu4lCnBTePdGlrkedudBFwBMsgc61bJ4bv9sWVTRVbKXfzbOc4eMNM 3Q4nX/22mwllEjODo3oY1WRDzrRyqytds3gnuQw1NEYdxGBxdHnNaD9t7fSp61YSaQ PdoZ3ksT+y8iUk9/yf8LYmz2wvKAYAKIo4QtKcnY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Stancek , "Peter Zijlstra (Intel)" , Will Deacon , Waiman Long , Linus Torvalds , Thomas Gleixner , dbueso@suse.de, Ingo Molnar , Sasha Levin Subject: [PATCH 5.2 043/143] locking/rwsem: Add missing ACQUIRE to read_slowpath exit when queue is empty Date: Wed, 4 Sep 2019 19:53:06 +0200 Message-Id: <20190904175315.753872440@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190904175314.206239922@linuxfoundation.org> References: <20190904175314.206239922@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [ Upstream commit e1b98fa316648420d0434d9ff5b92ad6609ba6c3 ] LTP mtest06 has been observed to occasionally hit "still mapped when deleted" and following BUG_ON on arm64. The extra mapcount originated from pagefault handler, which handled pagefault for vma that has already been detached. vma is detached under mmap_sem write lock by detach_vmas_to_be_unmapped(), which also invalidates vmacache. When the pagefault handler (under mmap_sem read lock) calls find_vma(), vmacache_valid() wrongly reports vmacache as valid. After rwsem down_read() returns via 'queue empty' path (as of v5.2), it does so without an ACQUIRE on sem->count: down_read() __down_read() rwsem_down_read_failed() __rwsem_down_read_failed_common() raw_spin_lock_irq(&sem->wait_lock); if (list_empty(&sem->wait_list)) { if (atomic_long_read(&sem->count) >= 0) { raw_spin_unlock_irq(&sem->wait_lock); return sem; The problem can be reproduced by running LTP mtest06 in a loop and building the kernel (-j $NCPUS) in parallel. It does reproduces since v4.20 on arm64 HPE Apollo 70 (224 CPUs, 256GB RAM, 2 nodes). It triggers reliably in about an hour. The patched kernel ran fine for 10+ hours. Signed-off-by: Jan Stancek Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Will Deacon Acked-by: Waiman Long Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dbueso@suse.de Fixes: 4b486b535c33 ("locking/rwsem: Exit read lock slowpath if queue empty & no writer") Link: https://lkml.kernel.org/r/50b8914e20d1d62bb2dee42d342836c2c16ebee7.1563438048.git.jstancek@redhat.com Signed-off-by: Ingo Molnar Acked-by: Jan Stancek Signed-off-by: Sasha Levin --- kernel/locking/rwsem-xadd.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 0b1f779572402..397dedc58432d 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -454,6 +454,8 @@ __rwsem_down_read_failed_common(struct rw_semaphore *sem, int state) * been set in the count. */ if (atomic_long_read(&sem->count) >= 0) { + /* Provide lock ACQUIRE */ + smp_acquire__after_ctrl_dep(); raw_spin_unlock_irq(&sem->wait_lock); rwsem_set_reader_owned(sem); lockevent_inc(rwsem_rlock_fast); -- 2.20.1