01-29-2009
Shouldn't the processes post on the semaphore when they're done? And what's so magical about ten, why can ten processes safely share it but not eleven?
semctl can tell you the last time a semop happened to something, but not who did it, or what. I don't think it 'remembers' who has 'access' beyond the normal scope of a sem either; it either suspends processes or not depending on its current value, and keeps a list or waiters to wake when posted on. Perhaps the sem's other access control features can be used to control what processes can wait on it, changing the process' group ID's and such.
Last edited by Corona688; 01-29-2009 at 12:39 PM..
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LEARN ABOUT OSX
sem_unlink
SEM_UNLINK(2) BSD System Calls Manual SEM_UNLINK(2)
NAME
sem_unlink -- remove a named semaphore
SYNOPSIS
#include <semaphore.h>
int
sem_unlink(const char *name);
DESCRIPTION
The named semaphore named name is removed. If the semaphore is in use by other processes, then name is immediately disassociated with the
semaphore, but the semaphore itself will not be removed until all references to it have been closed. Subsequent calls to sem_open() using
name will refer to or create a new semaphore named name.
If successful, sem_unlink() will return 0. Otherwise, -1 is returned and errno is set, and the state of the semaphore is unchanged.
ERRORS
sem_unlink() succeeds unless:
[EACCES] Permission is denied to be remove the semaphore.
[ENAMETOOLONG] name exceeded SEM_NAME_LEN characters.
[ENOENT] The named semaphore does not exist.
SEE ALSO
sem_close(2), sem_open(2), semctl(2), semget(2), semop(2)
HISTORY
sem_unlink() is specified in the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995).
Darwin June 8, 2000 Darwin