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[185.231.240.75]) by mx.google.com with ESMTPS id b22si28392468lji.74.2019.04.30.02.53.59 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 30 Apr 2019 02:53:59 -0700 (PDT) Received-SPF: pass (google.com: domain of ktkhai@virtuozzo.com designates 185.231.240.75 as permitted sender) client-ip=185.231.240.75; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ktkhai@virtuozzo.com designates 185.231.240.75 as permitted sender) smtp.mailfrom=ktkhai@virtuozzo.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=virtuozzo.com Received: from [172.16.25.169] by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1hLPSS-0007ia-U6; Tue, 30 Apr 2019 12:53:53 +0300 Subject: Re: [PATCH 1/3] mm: get_cmdline use arg_lock instead of mmap_sem To: Cyrill Gorcunov Cc: =?UTF-8?Q?Michal_Koutn=c3=bd?= , akpm@linux-foundation.org, arunks@codeaurora.org, brgl@bgdev.pl, geert+renesas@glider.be, ldufour@linux.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mguzik@redhat.com, mhocko@kernel.org, rppt@linux.ibm.com, vbabka@suse.cz References: <20190418182321.GJ3040@uranus.lan> <20190430081844.22597-1-mkoutny@suse.com> <20190430081844.22597-2-mkoutny@suse.com> <4c79fb09-c310-4426-68f7-8b268100359a@virtuozzo.com> <20190430093808.GD2673@uranus.lan> From: Kirill Tkhai Message-ID: <1a7265fa-610b-1f2a-e55f-b3a307a39bf2@virtuozzo.com> Date: Tue, 30 Apr 2019 12:53:51 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190430093808.GD2673@uranus.lan> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 30.04.2019 12:38, Cyrill Gorcunov wrote: > On Tue, Apr 30, 2019 at 12:09:57PM +0300, Kirill Tkhai wrote: >> >> This looks OK for me. >> >> But speaking about existing code it's a secret for me, why we ignore arg_lock >> in binfmt code, e.g. in load_elf_binary(). > > Well, strictly speaking we probably should but you know setup of > the @arg_start by kernel's elf loader doesn't cause any side > effects as far as I can tell (its been working this lockless > way for years, mmap_sem is taken later in the loader code). > Though for consistency sake we probably should set it up > under the spinlock. Ok, so elf loader doesn't change these parameters. Thanks for the explanation.