From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751648AbXDMCoB (ORCPT ); Thu, 12 Apr 2007 22:44:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751652AbXDMCoB (ORCPT ); Thu, 12 Apr 2007 22:44:01 -0400 Received: from smtp.osdl.org ([65.172.181.24]:44034 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751648AbXDMCoA (ORCPT ); Thu, 12 Apr 2007 22:44:00 -0400 Date: Thu, 12 Apr 2007 19:43:52 -0700 From: Andrew Morton To: Cc: Subject: Re: Cheap lock for user mode processes release when process exits Message-Id: <20070412194352.a29de6f5.akpm@linux-foundation.org> In-Reply-To: <20070413015428.AMJ80009@dougfood.mirapoint.com> References: <20070413015428.AMJ80009@dougfood.mirapoint.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 13 Apr 2007 01:54:28 +0000 (GMT) wrote: > Hi all, > > Maybe someone here knows better. > > I have several user-mode processes using shared mmap. There can be several reader processes and only one writer. Readers access the shared region frequently, writer seldom. > > Naturally, multi-reader/single-writer locks works best. I tried this with futex on 2.6.9-42.EL. However, if one of the processes is killed/exits, the lock doesn't get released. > > I can trap the signal to release the lock, but not all signals like kill. > > Anyway I can achieve this without a potential deadlock? > Robust futexes: http://lwn.net/Articles/172149/ But I don't know whether RH backported them into RHEL4.