X-Recipient: archive-cygwin@delorie.com X-SWARE-Spam-Status: No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,RFC_ABUSE_POST,T_TO_NO_BRKTS_FREEMAIL X-Spam-Check-By: sourceware.org MIME-Version: 1.0 In-Reply-To: <20110112111520.GJ6353@calimero.vinschen.de> References: <4D2C6AE0.1000703@redhat.com> <20110112111520.GJ6353@calimero.vinschen.de> Date: Wed, 12 Jan 2011 13:03:27 +0100 Message-ID: Subject: Re: Adding madvise function in cygwin with a #define From: jdzstz - gmail dot com To: cygwin@cygwin.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com I have readed again the Linux man page http://www.kernel.org/doc/man-pages/online/pages/man2/madvise.2.html and perhaps the first text is outdated. At the beginning of man page=A0it=A0says that: "This call does not influence=A0the semantics of the application (except in the case of MADV_DONTNEED), but=A0may influence its performance." And "The kernel is free to ignore the advice." But, in the other side, at the bottom it speaks about "flags which affect the memory mapping behaviour on fork" as you said in your email =3D> MADV_REMOVE, MADV_DONTFORK, MADV_DOFORK, etc... and to ignore it can be dangerous to application. Maybe an implementation option could be: 1) Standard advices that only has a influence in application performance, can be executed as current posix_madvise, checking only the parameters and doing nothing =3D> MADV_NORMAL, MADV_SEQUENTIAL, MADV_RANDOM, MADV_REMOVE, MADV_WILLNEED, MADV_DONTNEED 2) Rest of advices, that can modify the behaviour of application and generate errors or security problems, so madvise returns always "EINVAL" (as you said in your mail) : MADV_REMOVE, MADV_DONTFORK, MADV_DOFORK, MADV_HWPOISON, MADV_SOFT_OFFLINE, MADV_MERGEABLE, MADV_UNMERGEABLE To reduce problems with applications that uses advises of list number 2, this constants would be undefined, so if the aplication code make for example an "madvise(p, sz, MADV_DONTFORK)" at least, the problem will be detected at compilation time. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple