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=-8.5 required=3.0 tests=INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 C9D40C0044C for ; Mon, 5 Nov 2018 06:51:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 56FCA2081D for ; Mon, 5 Nov 2018 06:51:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 56FCA2081D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729403AbeKEQJS (ORCPT ); Mon, 5 Nov 2018 11:09:18 -0500 Received: from mx2.suse.de ([195.135.220.15]:34302 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728955AbeKEQJS (ORCPT ); Mon, 5 Nov 2018 11:09:18 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 56B7CB002; Mon, 5 Nov 2018 06:51:07 +0000 (UTC) Date: Mon, 5 Nov 2018 07:51:05 +0100 From: Michal Hocko To: Yangtao Li Cc: akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, vbabka@suse.cz, yang.shi@linux.alibaba.com, rientjes@google.com, linux@dominikbrodowski.net, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: mmap: remove unnecessary unlikely() Message-ID: <20181105065037.GA4361@dhcp22.suse.cz> References: <20181104124456.3424-1-tiny.windzz@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181104124456.3424-1-tiny.windzz@gmail.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun 04-11-18 07:44:56, Yangtao Li wrote: > WARN_ON() already contains an unlikely(), so it's not necessary to use > unlikely. We should just get rid of this ugliness altogether. It no longer serves its purpose. This is a historical artifact from 2005 where do_brk was called outside of the core mm. We do have a proper abstraction in vm_brk_flags and that one does the locking properly. > > Signed-off-by: Yangtao Li > --- > mm/mmap.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/mm/mmap.c b/mm/mmap.c > index 6c04292e16a7..2077008ade0c 100644 > --- a/mm/mmap.c > +++ b/mm/mmap.c > @@ -2965,10 +2965,8 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size, > static inline void verify_mm_writelocked(struct mm_struct *mm) > { > #ifdef CONFIG_DEBUG_VM > - if (unlikely(down_read_trylock(&mm->mmap_sem))) { > - WARN_ON(1); > + if (WARN_ON(down_read_trylock(&mm->mmap_sem))) > up_read(&mm->mmap_sem); > - } > #endif > } > > -- > 2.17.0 > -- Michal Hocko SUSE Labs