static void
lwp0busy(void)
{
/* busy lwp0 */
KASSERT(curlwp == NULL || curlwp->l_stat != LSONPROC);
rumpuser_mutex_enter_nowrap(lwp0mtx);
while (lwp0isbusy)
rumpuser_cv_wait_nowrap(lwp0cv, lwp0mtx);
lwp0isbusy = true;
rumpuser_mutex_exit(lwp0mtx);
}
static void
biothread(void *arg)
{
DEFINE_WAIT(w);
int i, flags, did;
/* for the bio callback */
rumpuser__hyp.hyp_schedule();
rumpuser__hyp.hyp_lwproc_newlwp(0);
rumpuser__hyp.hyp_unschedule();
for (;;) {
rumpuser_mutex_enter_nowrap(bio_mtx);
while (bio_outstanding_total == 0) {
rumpuser_cv_wait_nowrap(bio_cv, bio_mtx);
}
rumpuser_mutex_exit(bio_mtx);
/*
* if we made any progress, recheck. could be batched,
* but since currently locks are free here ... meh
*/
local_irq_save(flags);
for (did = 0;;) {
for (i = 0; i < NBLKDEV; i++) {
if (blkdev_outstanding[i])
did += blkfront_aio_poll(blkdevs[i]);
}
if (did)
break;
add_waiter(w, blkfront_queue);
local_irq_restore(flags);
schedule();
local_irq_save(flags);
}
local_irq_restore(flags);
}
}
/*
* Schedule a CPU. This optimizes for the case where we schedule
* the same thread often, and we have nCPU >= nFrequently-Running-Thread
* (where CPU is virtual rump cpu, not host CPU).
*/
void
rump_schedule_cpu_interlock(struct lwp *l, void *interlock)
{
struct rumpcpu *rcpu;
struct cpu_info *ci;
void *old;
bool domigrate;
bool bound = l->l_pflag & LP_BOUND;
l->l_stat = LSRUN;
/*
* First, try fastpath: if we were the previous user of the
* CPU, everything is in order cachewise and we can just
* proceed to use it.
*
* If we are a different thread (i.e. CAS fails), we must go
* through a memory barrier to ensure we get a truthful
* view of the world.
*/
KASSERT(l->l_target_cpu != NULL);
rcpu = cpuinfo_to_rumpcpu(l->l_target_cpu);
if (atomic_cas_ptr(&rcpu->rcpu_prevlwp, l, RCPULWP_BUSY) == l) {
if (interlock == rcpu->rcpu_mtx)
rumpuser_mutex_exit(rcpu->rcpu_mtx);
SCHED_FASTPATH(rcpu);
/* jones, you're the man */
goto fastlane;
}
/*
* Else, it's the slowpath for us. First, determine if we
* can migrate.
*/
if (ncpu == 1)
domigrate = false;
else
domigrate = true;
/* Take lock. This acts as a load barrier too. */
if (interlock != rcpu->rcpu_mtx)
rumpuser_mutex_enter_nowrap(rcpu->rcpu_mtx);
for (;;) {
SCHED_SLOWPATH(rcpu);
old = atomic_swap_ptr(&rcpu->rcpu_prevlwp, RCPULWP_WANTED);
/* CPU is free? */
if (old != RCPULWP_BUSY && old != RCPULWP_WANTED) {
if (atomic_cas_ptr(&rcpu->rcpu_prevlwp,
RCPULWP_WANTED, RCPULWP_BUSY) == RCPULWP_WANTED) {
break;
}
}
/*
* Do we want to migrate once?
* This may need a slightly better algorithm, or we
* might cache pingpong eternally for non-frequent
* threads.
*/
if (domigrate && !bound) {
domigrate = false;
SCHED_MIGRATED(rcpu);
rumpuser_mutex_exit(rcpu->rcpu_mtx);
rcpu = getnextcpu();
rumpuser_mutex_enter_nowrap(rcpu->rcpu_mtx);
continue;
}
/* Want CPU, wait until it's released an retry */
rcpu->rcpu_wanted++;
rumpuser_cv_wait_nowrap(rcpu->rcpu_cv, rcpu->rcpu_mtx);
rcpu->rcpu_wanted--;
}
rumpuser_mutex_exit(rcpu->rcpu_mtx);
fastlane:
ci = rcpu->rcpu_ci;
l->l_cpu = l->l_target_cpu = ci;
l->l_mutex = rcpu->rcpu_ci->ci_schedstate.spc_mutex;
l->l_ncsw++;
l->l_stat = LSONPROC;
/*
* No interrupts, so ci_curlwp === cpu_onproc.
* Okay, we could make an attempt to not set cpu_onproc
* in the case that an interrupt is scheduled immediately
* after a user proc, but leave that for later.
*/
ci->ci_curlwp = ci->ci_data.cpu_onproc = l;
}
