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using POSIX semaphores more robust on Darwin 1.2/Mac OS X Public Beta. this is for the version of 7.1 available via anon cvs as of Jan 14 2001 14:00 PST. since the semaphores and shared memory created by this emulator are shared with the backends via fork(), their persistent names are not necessary. removing their names with shm_unlink() and sem_unlink() after creation obviates the need for any "ipcclean" function. further, without these changes, the shared memory (and, therefore, the semaphores) will not be re-initialized/re-created after the first execution of the postmaster, until reboot or until some (non-existent) ipcclean function is executed. this patch does the following: 1) if the shared memory segment "SysV_Sem_Info" already existed, it is cleaned up. it shouldn't be there anyways. 2) the real indicator for whether the shared memory/semaphore emulator has been initialized is if "SemInfo" has been initialized. the shared memory and semaphores must be initialized regardless of whether there was a garbage shared memory segment lying around. 3) the shared memory segment "SysV_Sem_Info" is created with "O_EXCL" to catch the case where two postmasters might be starting simultaneously, so they don't both end up with the same shared memory (one will fail). note that this can't be done with the semaphores because Darwin 1.2 has a bug where attempting to open an existing semaphore with "O_EXCL" set will ruin the semaphore until the next reboot. 4) the shared memory segment "SysV_Sem_Info" is unlinked after it is created. it will then exist without a name until the postmaster and all backend children exit. 5) all semaphores are unlinked after they are created. they'll then exist without names until the postmaster and all backend children exit. -michael thornburgh, zenomt@armory.com |
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register.txt |
PostgreSQL Data Base Management System (formerly known as Postgres, then as Postgres95). This directory contains the development version of 7.1 of the PostgreSQL database server. The server is not ANSI SQL compliant, but it gets closer with every release. After you unzip and untar the distribution file, look at file INSTALL for the installation notes and file HISTORY for the changes. The latest version of this software may be obtained at ftp://ftp.postgresql.org/pub/. For more information look at our WWW home page located at http://www.postgreSQL.org/. PostgreSQL is not public domain software. It is copyrighted by the University of California but may be used according to the licensing terms of the the copyright below: ------------------------------------------------------------------------ POSTGRES95 Data Base Management System (formerly known as Postgres, then as Postgres95). Copyright (c) 1994-7 Regents of the University of California Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies. IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATIONS TO PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.