int tick_resume_broadcast_oneshot(struct clock_event_device *bc) { clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT); if(!cpus_empty(tick_broadcast_oneshot_mask)) tick_broadcast_set_event(ktime_get(), 1); return cpu_isset(smp_processor_id(), tick_broadcast_oneshot_mask); }
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state) { struct clock_event_device *bc, *dev; int cpu, ret = 0; ktime_t now; /* * If there is no broadcast device, tell the caller not to go * into deep idle. */ if (!tick_broadcast_device.evtdev) return -EBUSY; dev = this_cpu_ptr(&tick_cpu_device)->evtdev; raw_spin_lock(&tick_broadcast_lock); bc = tick_broadcast_device.evtdev; cpu = smp_processor_id(); if (state == TICK_BROADCAST_ENTER) { /* * If the current CPU owns the hrtimer broadcast * mechanism, it cannot go deep idle and we do not add * the CPU to the broadcast mask. We don't have to go * through the EXIT path as the local timer is not * shutdown. */ ret = broadcast_needs_cpu(bc, cpu); if (ret) goto out; /* * If the broadcast device is in periodic mode, we * return. */ if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) { /* If it is a hrtimer based broadcast, return busy */ if (bc->features & CLOCK_EVT_FEAT_HRTIMER) ret = -EBUSY; goto out; } if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) { WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask)); /* Conditionally shut down the local timer. */ broadcast_shutdown_local(bc, dev); /* * We only reprogram the broadcast timer if we * did not mark ourself in the force mask and * if the cpu local event is earlier than the * broadcast event. If the current CPU is in * the force mask, then we are going to be * woken by the IPI right away; we return * busy, so the CPU does not try to go deep * idle. */ if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) { ret = -EBUSY; } else if (dev->next_event < bc->next_event) { tick_broadcast_set_event(bc, cpu, dev->next_event); /* * In case of hrtimer broadcasts the * programming might have moved the * timer to this cpu. If yes, remove * us from the broadcast mask and * return busy. */ ret = broadcast_needs_cpu(bc, cpu); if (ret) { cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask); } } } } else { if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) { clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT); /* * The cpu which was handling the broadcast * timer marked this cpu in the broadcast * pending mask and fired the broadcast * IPI. So we are going to handle the expired * event anyway via the broadcast IPI * handler. No need to reprogram the timer * with an already expired event. */ if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_pending_mask)) goto out; /* * Bail out if there is no next event. */ if (dev->next_event == KTIME_MAX) goto out; /* * If the pending bit is not set, then we are * either the CPU handling the broadcast * interrupt or we got woken by something else. * * We are not longer in the broadcast mask, so * if the cpu local expiry time is already * reached, we would reprogram the cpu local * timer with an already expired event. * * This can lead to a ping-pong when we return * to idle and therefor rearm the broadcast * timer before the cpu local timer was able * to fire. This happens because the forced * reprogramming makes sure that the event * will happen in the future and depending on * the min_delta setting this might be far * enough out that the ping-pong starts. * * If the cpu local next_event has expired * then we know that the broadcast timer * next_event has expired as well and * broadcast is about to be handled. So we * avoid reprogramming and enforce that the * broadcast handler, which did not run yet, * will invoke the cpu local handler. * * We cannot call the handler directly from * here, because we might be in a NOHZ phase * and we did not go through the irq_enter() * nohz fixups. */ now = ktime_get(); if (dev->next_event <= now) { cpumask_set_cpu(cpu, tick_broadcast_force_mask); goto out; } /* * We got woken by something else. Reprogram * the cpu local timer device. */ tick_program_event(dev->next_event, 1); } } out: raw_spin_unlock(&tick_broadcast_lock); return ret; }
/* * Handle oneshot mode broadcasting */ static void tick_handle_oneshot_broadcast(struct clock_event_device *dev) { struct tick_device *td; ktime_t now, next_event; int cpu, next_cpu = 0; bool bc_local; raw_spin_lock(&tick_broadcast_lock); dev->next_event = KTIME_MAX; next_event = KTIME_MAX; cpumask_clear(tmpmask); now = ktime_get(); /* Find all expired events */ for_each_cpu(cpu, tick_broadcast_oneshot_mask) { /* * Required for !SMP because for_each_cpu() reports * unconditionally CPU0 as set on UP kernels. */ if (!IS_ENABLED(CONFIG_SMP) && cpumask_empty(tick_broadcast_oneshot_mask)) break; td = &per_cpu(tick_cpu_device, cpu); if (td->evtdev->next_event <= now) { cpumask_set_cpu(cpu, tmpmask); /* * Mark the remote cpu in the pending mask, so * it can avoid reprogramming the cpu local * timer in tick_broadcast_oneshot_control(). */ cpumask_set_cpu(cpu, tick_broadcast_pending_mask); } else if (td->evtdev->next_event < next_event) { next_event = td->evtdev->next_event; next_cpu = cpu; } } /* * Remove the current cpu from the pending mask. The event is * delivered immediately in tick_do_broadcast() ! */ cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask); /* Take care of enforced broadcast requests */ cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask); cpumask_clear(tick_broadcast_force_mask); /* * Sanity check. Catch the case where we try to broadcast to * offline cpus. */ if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask))) cpumask_and(tmpmask, tmpmask, cpu_online_mask); /* * Wakeup the cpus which have an expired event. */ bc_local = tick_do_broadcast(tmpmask); /* * Two reasons for reprogram: * * - The global event did not expire any CPU local * events. This happens in dyntick mode, as the maximum PIT * delta is quite small. * * - There are pending events on sleeping CPUs which were not * in the event mask */ if (next_event != KTIME_MAX) tick_broadcast_set_event(dev, next_cpu, next_event); raw_spin_unlock(&tick_broadcast_lock); if (bc_local) { td = this_cpu_ptr(&tick_cpu_device); td->evtdev->event_handler(td->evtdev); } }