From 978c03f9cf39e45871df8428dca0cc656e8ae967 Mon Sep 17 00:00:00 2001 From: Bruce Momjian Date: Wed, 17 Jan 2001 22:11:19 +0000 Subject: [PATCH] attached is a patch that makes SysV semaphore emulation 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 --- src/backend/port/darwin/sem.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/src/backend/port/darwin/sem.c b/src/backend/port/darwin/sem.c index c55090cedc..7dc7b0c919 100644 --- a/src/backend/port/darwin/sem.c +++ b/src/backend/port/darwin/sem.c @@ -10,7 +10,7 @@ * - this required changing sem_info from containig an array of sem_t to an array of sem_t* * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/port/darwin/Attic/sem.c,v 1.1 2000/12/11 00:49:54 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/port/darwin/Attic/sem.c,v 1.2 2001/01/17 22:11:19 momjian Exp $ * *------------------------------------------------------------------------- */ @@ -155,11 +155,13 @@ semget(key_t key, int nsems, int semflg) fd = shm_open(SHM_INFO_NAME, O_RDWR | O_CREAT | O_EXCL, MODE); if (fd == -1 && errno == EEXIST) { - exist = 1; - fd = shm_open(SHM_INFO_NAME, O_RDWR | O_CREAT, MODE); +/* exist = 1; */ + shm_unlink(SHM_INFO_NAME); + fd = shm_open(SHM_INFO_NAME, O_RDWR | O_CREAT | O_EXCL, MODE); } if (fd == -1) return fd; + shm_unlink(SHM_INFO_NAME); /* The size may only be set once. Ignore errors. */ ftruncate(fd, sizeof(struct sem_info)); SemInfo = mmap(NULL, sizeof(struct sem_info), @@ -174,6 +176,7 @@ semget(key_t key, int nsems, int semflg) fprintf(stderr, "darwin creating sem %s to cover shared mem.\n", semname); #endif SemInfo->sem = sem_open(semname, O_CREAT, semflg & 0777, 1); + sem_unlink(semname); sem_wait(SemInfo->sem); /* initilize shared memory */ memset(SemInfo->set, 0, sizeof(SemInfo->set)); @@ -244,6 +247,7 @@ fprintf(stderr, "darwin semget failed because if (nsems != 0 && SemInfo->set[sem fprintf(stderr, "darwin creating sem %s to cover set %d num %dm.\n", semname, semid, semnum); #endif SemInfo->set[semid].sem[semnum] = sem_open(semname, O_CREAT, semflg & 0777, 0); + sem_unlink(semname); /* Currently sem_init always returns -1. if( sem_init( &SemInfo->set[semid].sem[semnum], 1, 0 ) == -1 ) { -- 2.40.0