sem_open is required to return the same sem_t pointer for all
references to the same named semaphore when it's opened more than once
in the same process. thus we keep a table of all the mapped semaphores
and their reference counts. the code path for sem_close checked the
reference count, but then proceeded to unmap the semaphore regardless
of whether the count had reached zero.
add an immediate unlock-and-return for the nonzero refcnt case so the
property of performing the munmap syscall after releasing the lock can
be preserved.
int i;
LOCK(lock);
for (i=0; i<SEM_NSEMS_MAX && semtab[i].sem != sem; i++);
- if (!--semtab[i].refcnt) {
- semtab[i].sem = 0;
- semtab[i].ino = 0;
+ if (--semtab[i].refcnt) {
+ UNLOCK(lock);
+ return 0;
}
+ semtab[i].sem = 0;
+ semtab[i].ino = 0;
UNLOCK(lock);
munmap(sem, sizeof *sem);
return 0;