// Thread-safe allocation of a semaphore.
// Psema points at a kernel semaphore key.
// It starts out zero, meaning no semaphore.
// Fill it in, being careful of others calling initsema
// simultaneously.
static void
initsema(uint32 *psema)
{
uint32 sema;
if(*psema != 0) // already have one
return;
sema = mach_semcreate();
if(!cas(psema, 0, sema)){
// Someone else filled it in. Use theirs.
mach_semdestroy(sema);
return;
}
}
uintptr
runtime·semacreate(void)
{
return runtime·mach_semcreate();
}
