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[209.85.220.65]) by mx.google.com with SMTPS id q17sor4232445ljj.30.2019.04.30.02.38.10 for (Google Transport Security); Tue, 30 Apr 2019 02:38:10 -0700 (PDT) Received-SPF: pass (google.com: domain of gorcunov@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=ukGEBlNW; spf=pass (google.com: domain of gorcunov@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=gorcunov@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=zYjnml+G09Y2iH7YOBy1RnUmEBfOtgqF9A/Rh/pjRIY=; b=ukGEBlNWpw3ngsxHEBXIQvlOeQhk4/p8R6GklmoB2a/Xv4c2NAwqOW+cNq7yBLyL2B dBM9smuHxp7kZy66IxNEH6kzgwI4RJd82xvidtZDKhUdNbLaEsENurzJ+oj57ObbDtPs 2gPE4aJopsgxoW0EJ3MNExq6DgBsaZ+Kv6Jfluqf0CtBIn88GNQzHCmQolL80H1brM2K yijxEgwd99V9DqOpzUHXvBwaNvpoxs9k9tTcEX9MRgfaanxEYssrdayZTUb/xuilfH7/ y9GV0XIkScDJQx2nQUJrqtsIXjr2x18uJzzzUjE/TilqtUizxTCPjBmxTC6/AOgrlhFc HKig== X-Google-Smtp-Source: APXvYqxOGwnTEPiPGzR1pnewgUsAD0rmNHah8NK5uqndt/a8Ai7cN9+BqLVfK2dgtlDwZGL1HRdMqw== X-Received: by 2002:a2e:8648:: with SMTP id i8mr36897627ljj.166.1556617090058; Tue, 30 Apr 2019 02:38:10 -0700 (PDT) Received: from uranus.localdomain ([5.18.103.226]) by smtp.gmail.com with ESMTPSA id l16sm7876890lfk.44.2019.04.30.02.38.08 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 30 Apr 2019 02:38:09 -0700 (PDT) Received: by uranus.localdomain (Postfix, from userid 1000) id 840A24603CA; Tue, 30 Apr 2019 12:38:08 +0300 (MSK) Date: Tue, 30 Apr 2019 12:38:08 +0300 From: Cyrill Gorcunov To: Kirill Tkhai Cc: Michal =?iso-8859-1?Q?Koutn=FD?= , 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 Subject: Re: [PATCH 1/3] mm: get_cmdline use arg_lock instead of mmap_sem Message-ID: <20190430093808.GD2673@uranus.lan> References: <20190418182321.GJ3040@uranus.lan> <20190430081844.22597-1-mkoutny@suse.com> <20190430081844.22597-2-mkoutny@suse.com> <4c79fb09-c310-4426-68f7-8b268100359a@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4c79fb09-c310-4426-68f7-8b268100359a@virtuozzo.com> User-Agent: Mutt/1.11.3 (2019-02-01) 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 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.