From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933088AbaAaWfM (ORCPT ); Fri, 31 Jan 2014 17:35:12 -0500 Received: from mail-oa0-f43.google.com ([209.85.219.43]:37864 "EHLO mail-oa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932325AbaAaWfK convert rfc822-to-8bit (ORCPT ); Fri, 31 Jan 2014 17:35:10 -0500 From: "Network Nut" To: "'Austin S. Hemmelgarn'" , "'Clemens Ladisch'" Cc: References: <00d901cf1a19$0ea62db0$2bf28910$@gmail.com> <52E554EC.3090900@ladisch.de> <012d01cf1ae3$6543e340$2fcba9c0$@gmail.com> <52E6219A.3020405@ladisch.de> <00d001cf1b99$026407d0$072c1770$@gmail.com> <52E77282.4030303@ladisch.de> <009701cf1c6c$fbfaff50$f3f0fdf0$@gmail.com> <95b6e508-1358-4f01-9687-344e25bd4b2b@email.android.com> <00f201cf1e15$f134ce70$d39e6b50$@gmail.com> <52EBD7BC.5020704@gmail.com> In-Reply-To: <52EBD7BC.5020704@gmail.com> Subject: RE: WaitForMultipleObjects/etc. In Kernel Date: Fri, 31 Jan 2014 16:35:05 -0600 Message-ID: <007d01cf1ed4$b0e659a0$12b30ce0$@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Microsoft Outlook 14.0 Thread-Index: AQNT3acP/4y+UoGLob+8VizidhBl0AFz54/xAX6FO6UBfOQBmQGmz+ZcAX4/+oICHvy7eQGGlUFQAlIvzyACA4NB45cZb5Tg Content-Language: en-us Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > -----Original Message----- > From: Austin S. Hemmelgarn [mailto:ahferroin7@gmail.com] > Sent: Friday, January 31, 2014 11:05 AM > To: Network Nut; 'Clemens Ladisch' > Cc: linux-kernel@vger.kernel.org > Subject: Re: WaitForMultipleObjects/etc. In Kernel > >> Network Nut wrote: > > I was thinking that, rather than as for specifics, I should present my general > problem, and ask how long-time Linux experts would solve it. > > > > I have a master process M, that executes continually, from the birth to > death of user-session. > > > > I have many (distinct) processes that will be launched, and these > processes, P1, P2, ...Pn, expect to see that M is executing. These processes: > > > > 1. expect to have access to a shared-memory section that already exists > because M created it > > 2. expect to use a semaphore that already exists because M created it > > 3. expect to use a mutex that exists because M created it > > > > P1, P2, ...Pn all know the path of image on disk of M. They are also > permitted to maintain a fixed string that can be used to "get at" the mutex > and semaphore. > > > > How would P1, P2, ...Pn get at the semaphore that M created? > > > > Please note that M cannot have any prior knowledge at all of P1, P2, ...Pn. > P1...etc. must initiate communication with M. > > > > [I don't want to misuse/abuse linux-kernel with my personal questions, so > if there is a more appropriate group, please let me know.] > > > > Regards, > > > > -Net > Assuming that you're porting to mainline distributions (and not embedded > devices), named SHM segments are accessible (providing the accessing > process has correct permissions) under /dev/shm. You just need to make > sure that you create the segment with the right permissions for the > other processes to access it. Thanks, Austin. I already know how to do named shared memory between two processes. I only included that to describe my overall problem. The problem that I am having is how I can make three totally-independent processes interact: 1. M is a master process that creates a semaphore. 2. P1 is a process that operates against the semaphore. 3. P2 is a process that operates against the semaphore. 4. It is not permissible that M be responsible for launching P1 or P2. 5. The semaphore, one way or another, must allow itself to be specified as one of the synchronization primitives in epoll_wait() How do I do this? -Nut