static void
def_lock_release(void *lock)
{
Lock *l = (Lock *)lock;
if ((l->lock & WAFLAG) == 0)
atomic_add_rel_int(&l->lock, -RC_INCR);
else {
atomic_add_rel_int(&l->lock, -WAFLAG);
sigprocmask(SIG_SETMASK, &oldsigmask, NULL);
}
}
static void
def_lock_release(void *lock)
{
Lock *l;
l = (Lock *)lock;
if ((l->lock & WAFLAG) == 0)
atomic_add_rel_int(&l->lock, -RC_INCR);
else {
assert(wnested > 0);
atomic_add_rel_int(&l->lock, -WAFLAG);
if (atomic_fetchadd_int(&wnested, -1) == 1)
sigprocmask(SIG_SETMASK, &oldsigmask, NULL);
}
}
void
drm_gem_object_handle_reference(struct drm_gem_object *obj)
{
drm_gem_object_reference(obj);
atomic_add_rel_int(&obj->handle_count, 1);
}
/*
* Support Functions
*/
static void
ioat_submit_single(struct ioat_softc *ioat)
{
ioat_get(ioat, IOAT_ACTIVE_DESCR_REF);
atomic_add_rel_int(&ioat->head, 1);
atomic_add_rel_int(&ioat->hw_head, 1);
if (!ioat->is_completion_pending) {
ioat->is_completion_pending = TRUE;
callout_reset(&ioat->timer, IOAT_INTR_TIMO,
ioat_timer_callback, ioat);
}
ioat->stats.descriptors_submitted++;
}
/*
* Notification from the BPF framework that a buffer has moved into the held
* slot on a descriptor. Zero-copy BPF will update the shared page to let
* the user process know and flag the buffer as assigned if it hasn't already
* been marked assigned due to filling while it was in the store position.
*
* Note: identical logic as in bpf_zerocopy_buffull(), except that we operate
* on bd_hbuf and bd_hlen.
*/
void
bpf_zerocopy_bufheld(struct bpf_d *d)
{
struct zbuf *zb;
KASSERT(d->bd_bufmode == BPF_BUFMODE_ZBUF,
("bpf_zerocopy_bufheld: not in zbuf mode"));
zb = (struct zbuf *)d->bd_hbuf;
KASSERT(zb != NULL, ("bpf_zerocopy_bufheld: zb == NULL"));
if ((zb->zb_flags & ZBUF_FLAG_ASSIGNED) == 0) {
zb->zb_flags |= ZBUF_FLAG_ASSIGNED;
zb->zb_header->bzh_kernel_len = d->bd_hlen;
atomic_add_rel_int(&zb->zb_header->bzh_kernel_gen, 1);
}
}
/*
* All-CPU rendezvous. CPUs are signalled, all execute the setup function
* (if specified), rendezvous, execute the action function (if specified),
* rendezvous again, execute the teardown function (if specified), and then
* resume.
*
* Note that the supplied external functions _must_ be reentrant and aware
* that they are running in parallel and in an unknown lock context.
*/
void
smp_rendezvous_action(void)
{
struct thread *td;
void *local_func_arg;
void (*local_setup_func)(void*);
void (*local_action_func)(void*);
void (*local_teardown_func)(void*);
#ifdef INVARIANTS
int owepreempt;
#endif
/* Ensure we have up-to-date values. */
atomic_add_acq_int(&smp_rv_waiters[0], 1);
while (smp_rv_waiters[0] < smp_rv_ncpus)
cpu_spinwait();
/* Fetch rendezvous parameters after acquire barrier. */
local_func_arg = smp_rv_func_arg;
local_setup_func = smp_rv_setup_func;
local_action_func = smp_rv_action_func;
local_teardown_func = smp_rv_teardown_func;
/*
* Use a nested critical section to prevent any preemptions
* from occurring during a rendezvous action routine.
* Specifically, if a rendezvous handler is invoked via an IPI
* and the interrupted thread was in the critical_exit()
* function after setting td_critnest to 0 but before
* performing a deferred preemption, this routine can be
* invoked with td_critnest set to 0 and td_owepreempt true.
* In that case, a critical_exit() during the rendezvous
* action would trigger a preemption which is not permitted in
* a rendezvous action. To fix this, wrap all of the
* rendezvous action handlers in a critical section. We
* cannot use a regular critical section however as having
* critical_exit() preempt from this routine would also be
* problematic (the preemption must not occur before the IPI
* has been acknowledged via an EOI). Instead, we
* intentionally ignore td_owepreempt when leaving the
* critical section. This should be harmless because we do
* not permit rendezvous action routines to schedule threads,
* and thus td_owepreempt should never transition from 0 to 1
* during this routine.
*/
td = curthread;
td->td_critnest++;
#ifdef INVARIANTS
owepreempt = td->td_owepreempt;
#endif
/*
* If requested, run a setup function before the main action
* function. Ensure all CPUs have completed the setup
* function before moving on to the action function.
*/
if (local_setup_func != smp_no_rendevous_barrier) {
if (smp_rv_setup_func != NULL)
smp_rv_setup_func(smp_rv_func_arg);
atomic_add_int(&smp_rv_waiters[1], 1);
while (smp_rv_waiters[1] < smp_rv_ncpus)
cpu_spinwait();
}
if (local_action_func != NULL)
local_action_func(local_func_arg);
if (local_teardown_func != smp_no_rendevous_barrier) {
/*
* Signal that the main action has been completed. If a
* full exit rendezvous is requested, then all CPUs will
* wait here until all CPUs have finished the main action.
*/
atomic_add_int(&smp_rv_waiters[2], 1);
while (smp_rv_waiters[2] < smp_rv_ncpus)
cpu_spinwait();
if (local_teardown_func != NULL)
local_teardown_func(local_func_arg);
}
/*
* Signal that the rendezvous is fully completed by this CPU.
* This means that no member of smp_rv_* pseudo-structure will be
* accessed by this target CPU after this point; in particular,
* memory pointed by smp_rv_func_arg.
*
* The release semantic ensures that all accesses performed by
* the current CPU are visible when smp_rendezvous_cpus()
* returns, by synchronizing with the
* atomic_load_acq_int(&smp_rv_waiters[3]).
*/
atomic_add_rel_int(&smp_rv_waiters[3], 1);
td->td_critnest--;
KASSERT(owepreempt == td->td_owepreempt,
("rendezvous action changed td_owepreempt"));
}
