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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 B71DDC4361B for ; Tue, 15 Dec 2020 03:21:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B99A20721 for ; Tue, 15 Dec 2020 03:21:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727387AbgLODVo (ORCPT ); Mon, 14 Dec 2020 22:21:44 -0500 Received: from mail.kernel.org ([198.145.29.99]:36482 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726203AbgLODLP (ORCPT ); Mon, 14 Dec 2020 22:11:15 -0500 Date: Mon, 14 Dec 2020 19:08:59 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1608001740; bh=9uiPdRLVZJkkDatTBi0orKDJ2WyYqfzle2A9x9h+fQ4=; h=From:To:Subject:In-Reply-To:From; b=QAoFMctC6khPgDvL4iTtjWIV1w1GeA5/gOR+nTMnpWCVOUQODBjyoLnj4YQpNjQeH 1GW5tKotbwWQl1syh9HlFCaQn+wSgVRkWs384RqqA2glvpiDdner8Bbt0no4/DEQiI lZ6xsMyPPtBgYmH4icGxaCeUPefAD7FnuSE4LS2w= From: Andrew Morton To: akpm@linux-foundation.org, david@redhat.com, linux-mm@kvack.org, longman@redhat.com, mm-commits@vger.kernel.org, torvalds@linux-foundation.org, urezki@gmail.com, willy@infradead.org Subject: [patch 098/200] mm/vmalloc: Fix unlock order in s_stop() Message-ID: <20201215030859.OyhgKMLgu%akpm@linux-foundation.org> In-Reply-To: <20201214190237.a17b70ae14f129e2dca3d204@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Waiman Long Subject: mm/vmalloc: Fix unlock order in s_stop() When multiple locks are acquired, they should be released in reverse order. For s_start() and s_stop() in mm/vmalloc.c, that is not the case. s_start: mutex_lock(&vmap_purge_lock); spin_lock(&vmap_area_lock); s_stop : mutex_unlock(&vmap_purge_lock); spin_unlock(&vmap_area_lock); This unlock sequence, though allowed, is not optimal. If a waiter is present, mutex_unlock() will need to go through the slowpath of waking up the waiter with preemption disabled. Fix that by releasing the spinlock first before the mutex. Link: https://lkml.kernel.org/r/20201213180843.16938-1-longman@redhat.com Fixes: e36176be1c39 ("mm/vmalloc: rework vmap_area_lock") Signed-off-by: Waiman Long Reviewed-by: Uladzislau Rezki (Sony) Reviewed-by: David Hildenbrand Cc: Matthew Wilcox Signed-off-by: Andrew Morton --- mm/vmalloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/vmalloc.c~mm-vmalloc-fix-unlock-order-in-s_stop +++ a/mm/vmalloc.c @@ -3465,11 +3465,11 @@ static void *s_next(struct seq_file *m, } static void s_stop(struct seq_file *m, void *p) - __releases(&vmap_purge_lock) __releases(&vmap_area_lock) + __releases(&vmap_purge_lock) { - mutex_unlock(&vmap_purge_lock); spin_unlock(&vmap_area_lock); + mutex_unlock(&vmap_purge_lock); } static void show_numa_info(struct seq_file *m, struct vm_struct *v) _