From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f69.google.com (mail-pg0-f69.google.com [74.125.83.69]) by kanga.kvack.org (Postfix) with ESMTP id 6D7A96B0033 for ; Fri, 3 Nov 2017 14:17:07 -0400 (EDT) Received: by mail-pg0-f69.google.com with SMTP id y5so4194040pgq.15 for ; Fri, 03 Nov 2017 11:17:07 -0700 (PDT) Received: from out4439.biz.mail.alibaba.com (out4439.biz.mail.alibaba.com. [47.88.44.39]) by mx.google.com with ESMTPS id l197si6998579pga.371.2017.11.03.11.17.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 03 Nov 2017 11:17:06 -0700 (PDT) Subject: Re: [PATCH] mm: use in_atomic() in print_vma_addr() 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 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: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , mingo@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joe Perches 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 > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org