Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 22 Apr 2001 06:41:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 22 Apr 2001 06:41:34 -0400 Received: from [212.150.182.35] ([212.150.182.35]:27144 "EHLO exchange.guidelet.com") by vger.kernel.org with ESMTP id ; Sun, 22 Apr 2001 06:41:25 -0400 Message-ID: <041c01c0cb21$1dd520c0$910201c0@zapper> From: "Alon Ziv" To: In-Reply-To:

<9bqgvi$63q$1@penguin.transmeta.com> <3AE10741.FA4E40BD@gmx.de> Subject: Re: light weight user level semaphores Date: Sun, 22 Apr 2001 13:41:04 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4522.1200 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4522.1200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org All of this FD allocation stuff is truly distrurbing. This appears to be the one place where Win32 got it (almost) right--- quite about every kernel object looks to userland just like an opaque handle, and the same operations apply to all of them. So (e.g.) a mixed wait for socket operation or a semaphore or a timer is very simple. The only abstraction we have that is even remotely similar is the FD, yet its semantics are far too strict to use this way. The only remotely-feasible idea I've had, so far, was to allow "negative" FDs (i.e., numbered 0x80000000+) to be used for semaphores; this sidesteps the POSIX requirements (= we can just claim we don't support more than 2G FDs per process), but still leaves us with the problems of managing a split (or extremely large) FD table _and_ with the issue of allocation policy... Besides, as Linus already said, FDs are likely not the right abstraction for objects without file behavior, like semaphores or timers. [BTW, another solution is to truly support opaque "handles" to kernel objects; I believe David Howells is already working on something like this for Wine? The poll interface can be trivially extended to support waiting on those...] -az - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/