Ion Gaztañaga wrote:
Because that semaphore couldn't be placed in shared memory and memory-mapped files, like its POSIX equivalent with pshared set to true:
int sem_init(sem_t *sem, int pshared, unsigned int value);
That's not strictly true. Put an unique name in shared memory, and do something to cache the handle in accessing processes or the cost *will* suck. Unfortunately just basing things on POSIX is a pretty bad design decision if you want portability - if you manage it as 'a shared thing' and handles then its easier to implement with either, though POSIX is still generally crappy because its hard to avoid races to initialise the shared thing, and because its so badly defined what you can put it in. POSIX shared memory? SysV shared memory? Memory mapped file? memory mapped /dev/null? For a memory mapped file, does the semaphore state persist if the file is closed by all processes? What about closed by all processes, and the system is rebooted? Its a khazi, it really is. James