static void
scheduler(void *dummy)
{
struct scheduler_info info;
struct proc *p;
KKASSERT(!IN_CRITICAL_SECT(curthread));
loop:
scheduler_notify = 0;
/*
* Don't try to swap anything in if we are low on memory.
*/
if (vm_page_count_severe()) {
vm_wait(0);
goto loop;
}
/*
* Look for a good candidate to wake up
*
* XXX we should make the schedule thread pcpu and then use a
* segmented allproc scan.
*/
info.pp = NULL;
info.ppri = INT_MIN;
allproc_scan(scheduler_callback, &info, 0);
/*
* Nothing to do, back to sleep for at least 1/10 of a second. If
* we are woken up, immediately process the next request. If
* multiple requests have built up the first is processed
* immediately and the rest are staggered.
*/
if ((p = info.pp) == NULL) {
tsleep(&proc0, 0, "nowork", hz / 10);
if (scheduler_notify == 0)
tsleep(&scheduler_notify, 0, "nowork", 0);
goto loop;
}
/*
* Fault the selected process in, then wait for a short period of
* time and loop up.
*
* XXX we need a heuristic to get a measure of system stress and
* then adjust our stagger wakeup delay accordingly.
*/
lwkt_gettoken(&p->p_token);
faultin(p);
p->p_swtime = 0;
lwkt_reltoken(&p->p_token);
PRELE(p);
tsleep(&proc0, 0, "swapin", hz / 10);
goto loop;
}
/*
* Implement fork's actions on an address space.
* Here we arrange for the address space to be copied or referenced,
* allocate a user struct (pcb and kernel stack), then call the
* machine-dependent layer to fill those in and make the new process
* ready to run. The new process is set up so that it returns directly
* to user mode to avoid stack copying and relocation problems.
*
* No requirements.
*/
void
vm_fork(struct proc *p1, struct proc *p2, int flags)
{
if ((flags & RFPROC) == 0) {
/*
* Divorce the memory, if it is shared, essentially
* this changes shared memory amongst threads, into
* COW locally.
*/
if ((flags & RFMEM) == 0) {
if (p1->p_vmspace->vm_sysref.refcnt > 1) {
vmspace_unshare(p1);
}
}
cpu_fork(ONLY_LWP_IN_PROC(p1), NULL, flags);
return;
}
if (flags & RFMEM) {
vmspace_ref(p1->p_vmspace);
p2->p_vmspace = p1->p_vmspace;
}
while (vm_page_count_severe()) {
vm_wait(0);
}
if ((flags & RFMEM) == 0) {
p2->p_vmspace = vmspace_fork(p1->p_vmspace);
pmap_pinit2(vmspace_pmap(p2->p_vmspace));
if (p1->p_vmspace->vm_shm)
shmfork(p1, p2);
}
pmap_init_proc(p2);
}
