Re: patch for src/backend/port/darwin/sem.c

Thanks. Applied.

>
>
> 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(at)armory(dot)com
>
>
>
> *** src/backend/port/darwin/sem.c.orig Sun Jan 14 15:11:28 2001
> --- src/backend/port/darwin/sem.c Sun Jan 14 15:32:18 2001
> ***************
> *** 155,165 ****
> 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);
> }
> if (fd == -1)
> return fd;
> /* The size may only be set once. Ignore errors. */
> ftruncate(fd, sizeof(struct sem_info));
> SemInfo = mmap(NULL, sizeof(struct sem_info),
> --- 155,167 ----
> fd = shm_open(SHM_INFO_NAME, O_RDWR | O_CREAT | O_EXCL, MODE);
> if (fd == -1 && errno == EEXIST)
> {
> ! /* 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),
> ***************
> *** 174,179 ****
> --- 176,182 ----
> 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));
> ***************
> *** 244,249 ****
> --- 247,253 ----
> 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 ) {
>

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