From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 8 Oct 2008 01:57:37 +0200 From: Andi Kleen Subject: Re: [PATCH, v3] shmat: introduce flag SHM_MAP_NOT_FIXED Message-ID: <20081007235737.GD7971@one.firstfloor.org> References: <1223396117-8118-1-git-send-email-kirill@shutemov.name> <2f11576a0810070931k79eb72dfr838a96650563b93a@mail.gmail.com> <20081007211038.GQ20740@one.firstfloor.org> <20081008000518.13f48462@lxorguk.ukuu.org.uk> <20081007232059.GU20740@one.firstfloor.org> <20081008004030.7a0e9915@lxorguk.ukuu.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081008004030.7a0e9915@lxorguk.ukuu.org.uk> Sender: owner-linux-mm@kvack.org Return-Path: To: Alan Cox Cc: Andi Kleen , KOSAKI Motohiro , "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Ingo Molnar , Arjan van de Ven , Hugh Dickins , Ulrich Drepper , Andrew Morton List-ID: On Wed, Oct 08, 2008 at 12:40:30AM +0100, Alan Cox wrote: > > > Can use shm_open and mmap to get POSIX standard shm behaviour via a sane > > > > I don't think shm_open can attach to SYSV shared segments. Or are you > > proposing to add "sysvshmfs" to make that possible? > > Actually you can do so. As it stands today the SYS3 SHM interface code > does the following > > create a char array in the form SYS%08ld, key > open it on shmfs Perhaps I'm confused but my /dev/shm doesn't have any such files, but I see a variety of shm segments in ipcs. What would the path passed to shm_open look like? > > > - There are legacy interfaces that cannot be really changed who use sysv shm > > (e.g. X shm and others -- just do a ipcs on your system) > > They can be changed You want to break the X interface? And who knows who else is using it. > and nobody is wanting to map those at fixed addresses. You're saying it should always use the address as a search hint? Just changing the semantics unconditionally would seem risky to me. After all as you point out they are primarily for compatibility and for that keeping old semantics would seem better to me. -Andi -- ak@linux.intel.com -- 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