From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756253AbdKCSRC (ORCPT ); Fri, 3 Nov 2017 14:17:02 -0400 Received: from out0-217.mail.aliyun.com ([140.205.0.217]:36623 "EHLO out0-217.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751451AbdKCSRB (ORCPT ); Fri, 3 Nov 2017 14:17:01 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R441e4;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e02c03312;MF=yang.s@alibaba-inc.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---.9JX-ayR_1509733008; Subject: Re: [PATCH] mm: use in_atomic() in print_vma_addr() To: Andrew Morton Cc: Michal Hocko , mingo@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joe Perches References: <1509572313-102989-1-git-send-email-yang.s@alibaba-inc.com> <20171102075744.whhxjmqbdkfaxghd@dhcp22.suse.cz> <20171103110245.7049460a05cc18c7e8a9feb2@linux-foundation.org> From: "Yang Shi" Message-ID: <39320f9c-95fd-9cf6-6bd9-e31655168d43@alibaba-inc.com> Date: Sat, 04 Nov 2017 02:16:45 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20171103110245.7049460a05cc18c7e8a9feb2@linux-foundation.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/3/17 11:02 AM, Andrew Morton wrote: > On Fri, 03 Nov 2017 01:44:44 +0800 "Yang Shi" wrote: > >> I may not articulate it in the commit log > > You should have done so ;) Yes, definitely. I could done it much better. > > Here's the changelog I ended up with: > > : From: "Yang Shi" > : Subject: mm: use in_atomic() in print_vma_addr() > : > : 3e51f3c4004c9b ("sched/preempt: Remove PREEMPT_ACTIVE unmasking off > : in_atomic()") uses in_atomic() just check the preempt count, so it is not > : necessary to use preempt_count() in print_vma_addr() any more. Replace > : preempt_count() to in_atomic() which is a generic API for checking atomic > : context. > : > : in_atomic() is the preferred API for checking atomic context instead of > : preempt_count() which should be used for retrieving the preemption count > : value. > : > : If we go through the kernel code, almost everywhere "in_atomic" is used > : for such use case already, except two places: > : > : - print_vma_addr() > : - debug_smp_processor_id() > : > : Both came from Ingo long time ago before 3e51f3c4004c9b01 ("sched/preempt: > : Remove PREEMPT_ACTIVE unmasking off in_atomic()"). But, after this commit > : was merged, use in_atomic() to follow the convention. > : > : Link: http://lkml.kernel.org/r/1509572313-102989-1-git-send-email-yang.s@alibaba-inc.com > : Signed-off-by: Yang Shi > : Acked-by: Michal Hocko > : Cc: Frederic Weisbecker > : Cc: Ingo Molnar Thanks a lot for reworking the commit log. > > > > Also, checkpatch says > > WARNING: use of in_atomic() is incorrect outside core kernel code > #43: FILE: mm/memory.c:4491: > + if (in_atomic()) > > I don't recall why we did that, but perhaps this should be revisited? I think the rule for in_atomic is obsolete in checkpatch.pl. A quick grep shows in_atomic() is used by arch, drivers, crypto, even though the comment in include/linux/preempt.h says in_atomic() should be not used by drivers. However, the message could be ignored with --ignore=IN_ATOMIC. But, it sounds better to fix the wrong rule and maybe even the comment in include/linux/preempt.h since it sounds confusing. Thanks, Yang >