Something went wrong. Try again.
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Something went wrong. Try again.
1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991001011021031041051061071081091101111121131141151161171181191201211221231241251261271281291301311321331341351361371381391401411421431441451461471481491501511521531541551561571581591601611621631641651661671681691701711721731741751761771781791801811821831841851861871881891901911921931941951961971981992002012022032042052062072082092102112122132142152162172182192202212222232242252262272282292302312322332342352362372382392402412422432442452462472482492502512522532542552562572582592602612622632642652662672682692702712722732742752762772782792802812822832842852862872882892902912922932942952962972982993003013023033043053063073083093103113123133143153163173183193203213223233243253263273283293303313323333343353363373383393403413423433443453463473483493503513523533543553563573583593603613623633643653663673683693703713723733743753763773783793803813823833843853863873883893903913923933943953963973983994004014024034044054064074084094104114124134144154164174184194204214224234244254264274284294304314324334344354364374384394404414424434444454464474484494504514524534544554564574584594604614624634644654664674684694704714724734744754764774784794804814824834844854864874884894904914924934944954964974984995005015025035045055065075085095105115125135145155165175185195205215225235245255265275285295305315325335345355365375385395405415425435445455465475485495505515525535545555565575585595605615625635645655665675685695705715725735745755765775785795805815825835845855865875885895905915925935945955965975985996006016026036046056066076086096106116126136146156166176186196206216226236246256266276286296306316326336346356366376386396406416426436446456466476486496506516526536546556566576586596606616626636646656666676686696706716726736746756766776786796806816826836846856866876886896906916926936946956966976986997007017027037047057067077087097107117127137147157167177187197207217227237247257267277287297307317327337347357367377387397407417427437447457467477487497507517527537547557567577587597607617627637647657667677687697707717727737747757767777787797807817827837847857867877887897907917927937947957967977987998008018028038048058068078088098108118128138148158168178188198208218228238248258268278288298308318328338348358368378388398408418428438448458468478488498508518528538548558568578588598608618628638648658668678688698708718728738748758768778788798808818828838848858868878888898908918928938948958968978988999009019029039049059069079089099109119129139149159169179189199209219229239249259269279289299309319329339349359369379389399409419429439449459469479489499509519529539549559569579589599609619629639649659669679689699709719729739749759769779789799809819829839849859869879889899909919929939949959969979989991000100110021003100410051006100710081009101010111012101310141015101610171018101910201021102210231024102510261027102810291030103110321033103410351036103710381039104010411042104310441045104610471048104910501051105210531054105510561057105810591060106110621063106410651066106710681069107010711072107310741075107610771078107910801081108210831084108510861087108810891090109110921093109410951096109710981099110011011102110311041105110611071108110911101111111211131114111511161117111811191120112111221123112411251126112711281129113011311132113311341135113611371138113911401141114211431144114511461147114811491150115111521153115411551156115711581159116011611162116311641165116611671168116911701171117211731174117511761177117811791180118111821183118411851186118711881189119011911192119311941195119611971198119912001201120212031204120512061207120812091210121112121213121412151216121712181219122012211222122312241225122612271228122912301231123212331234123512361237123812391240124112421243124412451246124712481249// SPDX-License-Identifier: GPL-2.0/* * This file contains functions which emulate a local clock-event * device via a broadcast event source. * * Copyright(C) 2005-2006, Linutronix GmbH, Thomas Gleixner <tglx@kernel.org> * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner */#include <linux/cpu.h>#include <linux/err.h>#include <linux/hrtimer.h>#include <linux/interrupt.h>#include <linux/percpu.h>#include <linux/profile.h>#include <linux/sched.h>#include <linux/smp.h>#include <linux/module.h>
#include "tick-internal.h"
/* * Broadcast support for broken x86 hardware, where the local apic * timer stops in C3 state. */
static struct tick_device tick_broadcast_device;static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;static cpumask_var_t tmpmask __cpumask_var_read_mostly;static int tick_broadcast_forced;
static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
#ifdef CONFIG_TICK_ONESHOTstatic DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
static void tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic);static void tick_broadcast_clear_oneshot(int cpu);static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);# ifdef CONFIG_HOTPLUG_CPUstatic void tick_broadcast_oneshot_offline(unsigned int cpu);# endif#elsestatic inline voidtick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic) { BUG(); }static inline void tick_broadcast_clear_oneshot(int cpu) { }static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }# ifdef CONFIG_HOTPLUG_CPUstatic inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }# endif#endif
/* * Debugging: see timer_list.c */struct tick_device *tick_get_broadcast_device(void){ return &tick_broadcast_device;}
struct cpumask *tick_get_broadcast_mask(void){ return tick_broadcast_mask;}
static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
const struct clock_event_device *tick_get_wakeup_device(int cpu){ return tick_get_oneshot_wakeup_device(cpu);}
/* * Start the device in periodic mode */static void tick_broadcast_start_periodic(struct clock_event_device *bc){ if (bc) { bc->next_event_forced = 0; tick_setup_periodic(bc, 1); }}
/* * Check, if the device can be utilized as broadcast device: */static bool tick_check_broadcast_device(struct clock_event_device *curdev, struct clock_event_device *newdev){ if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) || (newdev->features & CLOCK_EVT_FEAT_PERCPU) || (newdev->features & CLOCK_EVT_FEAT_C3STOP)) return false;
if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT && !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) return false;
return !curdev || newdev->rating > curdev->rating;}
#ifdef CONFIG_TICK_ONESHOTstatic struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu){ return per_cpu(tick_oneshot_wakeup_device, cpu);}
static void tick_oneshot_wakeup_handler(struct clock_event_device *wd){ wd->next_event_forced = 0; /* * If we woke up early and the tick was reprogrammed in the * meantime then this may be spurious but harmless. */ tick_receive_broadcast();}
static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev, int cpu){ struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
if (!newdev) goto set_device;
if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) || (newdev->features & CLOCK_EVT_FEAT_C3STOP)) return false;
if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) || !(newdev->features & CLOCK_EVT_FEAT_ONESHOT)) return false;
if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) return false;
if (curdev && newdev->rating <= curdev->rating) return false;
if (!try_module_get(newdev->owner)) return false;
newdev->event_handler = tick_oneshot_wakeup_handler;set_device: clockevents_exchange_device(curdev, newdev); per_cpu(tick_oneshot_wakeup_device, cpu) = newdev; return true;}#elsestatic struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu){ return NULL;}
static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev, int cpu){ return false;}#endif
/* * Conditionally install/replace broadcast device */void tick_install_broadcast_device(struct clock_event_device *dev, int cpu){ struct clock_event_device *cur = tick_broadcast_device.evtdev;
if (tick_set_oneshot_wakeup_device(dev, cpu)) return;
if (!tick_check_broadcast_device(cur, dev)) return;
if (!try_module_get(dev->owner)) return;
clockevents_exchange_device(cur, dev); if (cur) cur->event_handler = clockevents_handle_noop; tick_broadcast_device.evtdev = dev; if (!cpumask_empty(tick_broadcast_mask)) tick_broadcast_start_periodic(dev);
if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT)) return;
/* * If the system already runs in oneshot mode, switch the newly * registered broadcast device to oneshot mode explicitly. */ if (tick_broadcast_oneshot_active()) { tick_broadcast_switch_to_oneshot(); return; }
/* * Inform all cpus about this. We might be in a situation * where we did not switch to oneshot mode because the per cpu * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack * of a oneshot capable broadcast device. Without that * notification the systems stays stuck in periodic mode * forever. */ tick_clock_notify();}
/* * Check, if the device is the broadcast device */int tick_is_broadcast_device(struct clock_event_device *dev){ return (dev && tick_broadcast_device.evtdev == dev);}
int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq){ int ret = -ENODEV;
if (tick_is_broadcast_device(dev)) { raw_spin_lock(&tick_broadcast_lock); ret = __clockevents_update_freq(dev, freq); raw_spin_unlock(&tick_broadcast_lock); } return ret;}
static void err_broadcast(const struct cpumask *mask){ pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");}
static void tick_device_setup_broadcast_func(struct clock_event_device *dev){ if (!dev->broadcast) dev->broadcast = tick_broadcast; if (!dev->broadcast) { pr_warn_once("%s depends on broadcast, but no broadcast function available\n", dev->name); dev->broadcast = err_broadcast; }}
/* * Check, if the device is dysfunctional and a placeholder, which * needs to be handled by the broadcast device. */int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu){ struct clock_event_device *bc = tick_broadcast_device.evtdev; unsigned long flags; int ret = 0;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
/* * Devices might be registered with both periodic and oneshot * mode disabled. This signals, that the device needs to be * operated from the broadcast device and is a placeholder for * the cpu local device. */ if (!tick_device_is_functional(dev)) { dev->event_handler = tick_handle_periodic; tick_device_setup_broadcast_func(dev); cpumask_set_cpu(cpu, tick_broadcast_mask); if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) tick_broadcast_start_periodic(bc); else tick_broadcast_setup_oneshot(bc, false); ret = 1; } else { /* * Clear the broadcast bit for this cpu if the * device is not power state affected. */ if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) cpumask_clear_cpu(cpu, tick_broadcast_mask); else tick_device_setup_broadcast_func(dev);
/* * Clear the broadcast bit if the CPU is not in * periodic broadcast on state. */ if (!cpumask_test_cpu(cpu, tick_broadcast_on)) cpumask_clear_cpu(cpu, tick_broadcast_mask);
switch (tick_broadcast_device.mode) { case TICKDEV_MODE_ONESHOT: /* * If the system is in oneshot mode we can * unconditionally clear the oneshot mask bit, * because the CPU is running and therefore * not in an idle state which causes the power * state affected device to stop. Let the * caller initialize the device. */ tick_broadcast_clear_oneshot(cpu); ret = 0; break;
case TICKDEV_MODE_PERIODIC: /* * If the system is in periodic mode, check * whether the broadcast device can be * switched off now. */ if (cpumask_empty(tick_broadcast_mask) && bc) clockevents_shutdown(bc); /* * If we kept the cpu in the broadcast mask, * tell the caller to leave the per cpu device * in shutdown state. The periodic interrupt * is delivered by the broadcast device, if * the broadcast device exists and is not * hrtimer based. */ if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER)) ret = cpumask_test_cpu(cpu, tick_broadcast_mask); break; default: break; } } raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags); return ret;}
int tick_receive_broadcast(void){ struct tick_device *td = this_cpu_ptr(&tick_cpu_device); struct clock_event_device *evt = td->evtdev;
if (!evt) return -ENODEV;
if (!evt->event_handler) return -EINVAL;
evt->event_handler(evt); return 0;}
/* * Broadcast the event to the cpus, which are set in the mask (mangled). */static bool tick_do_broadcast(struct cpumask *mask){ int cpu = smp_processor_id(); struct tick_device *td; bool local = false;
/* * Check, if the current cpu is in the mask */ if (cpumask_test_cpu(cpu, mask)) { struct clock_event_device *bc = tick_broadcast_device.evtdev;
cpumask_clear_cpu(cpu, mask); /* * We only run the local handler, if the broadcast * device is not hrtimer based. Otherwise we run into * a hrtimer recursion. * * local timer_interrupt() * local_handler() * expire_hrtimers() * bc_handler() * local_handler() * expire_hrtimers() */ local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER); }
if (!cpumask_empty(mask)) { /* * It might be necessary to actually check whether the devices * have different broadcast functions. For now, just use the * one of the first device. This works as long as we have this * misfeature only on x86 (lapic) */ td = &per_cpu(tick_cpu_device, cpumask_first(mask)); td->evtdev->broadcast(mask); } return local;}
/* * Periodic broadcast: * - invoke the broadcast handlers */static bool tick_do_periodic_broadcast(void){ cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask); return tick_do_broadcast(tmpmask);}
/* * Event handler for periodic broadcast ticks */static void tick_handle_periodic_broadcast(struct clock_event_device *dev){ struct tick_device *td = this_cpu_ptr(&tick_cpu_device); bool bc_local;
raw_spin_lock(&tick_broadcast_lock); tick_broadcast_device.evtdev->next_event_forced = 0;
/* Handle spurious interrupts gracefully */ if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) { raw_spin_unlock(&tick_broadcast_lock); return; }
bc_local = tick_do_periodic_broadcast();
if (clockevent_state_oneshot(dev)) { ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
clockevents_program_event(dev, next, true); } raw_spin_unlock(&tick_broadcast_lock);
/* * We run the handler of the local cpu after dropping * tick_broadcast_lock because the handler might deadlock when * trying to switch to oneshot mode. */ if (bc_local) td->evtdev->event_handler(td->evtdev);}
/** * tick_broadcast_control - Enable/disable or force broadcast mode * @mode: The selected broadcast mode * * Called when the system enters a state where affected tick devices * might stop. Note: TICK_BROADCAST_FORCE cannot be undone. */void tick_broadcast_control(enum tick_broadcast_mode mode){ struct clock_event_device *bc, *dev; struct tick_device *td; int cpu, bc_stopped; unsigned long flags;
/* Protects also the local clockevent device. */ raw_spin_lock_irqsave(&tick_broadcast_lock, flags); td = this_cpu_ptr(&tick_cpu_device); dev = td->evtdev;
/* * Is the device not affected by the powerstate ? */ if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP)) goto out;
if (!tick_device_is_functional(dev)) goto out;
cpu = smp_processor_id(); bc = tick_broadcast_device.evtdev; bc_stopped = cpumask_empty(tick_broadcast_mask);
switch (mode) { case TICK_BROADCAST_FORCE: tick_broadcast_forced = 1; fallthrough; case TICK_BROADCAST_ON: cpumask_set_cpu(cpu, tick_broadcast_on); if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) { /* * Only shutdown the cpu local device, if: * * - the broadcast device exists * - the broadcast device is not a hrtimer based one * - the broadcast device is in periodic mode to * avoid a hiccup during switch to oneshot mode */ if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) && tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) clockevents_shutdown(dev); } break;
case TICK_BROADCAST_OFF: if (tick_broadcast_forced) break; cpumask_clear_cpu(cpu, tick_broadcast_on); if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) { if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) tick_setup_periodic(dev, 0); } break; }
if (bc) { if (cpumask_empty(tick_broadcast_mask)) { if (!bc_stopped) clockevents_shutdown(bc); } else if (bc_stopped) { if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) tick_broadcast_start_periodic(bc); else tick_broadcast_setup_oneshot(bc, false); } }out: raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);}EXPORT_SYMBOL_GPL(tick_broadcast_control);
/* * Set the periodic handler depending on broadcast on/off */void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast){ if (!broadcast) dev->event_handler = tick_handle_periodic; else dev->event_handler = tick_handle_periodic_broadcast;}
#ifdef CONFIG_HOTPLUG_CPUstatic void tick_shutdown_broadcast(void){ struct clock_event_device *bc = tick_broadcast_device.evtdev;
if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) { if (bc && cpumask_empty(tick_broadcast_mask)) clockevents_shutdown(bc); }}
/* * Remove a CPU from broadcasting */void tick_broadcast_offline(unsigned int cpu){ raw_spin_lock(&tick_broadcast_lock); cpumask_clear_cpu(cpu, tick_broadcast_mask); cpumask_clear_cpu(cpu, tick_broadcast_on); tick_broadcast_oneshot_offline(cpu); tick_shutdown_broadcast(); raw_spin_unlock(&tick_broadcast_lock);}
#endif
void tick_suspend_broadcast(void){ struct clock_event_device *bc; unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
bc = tick_broadcast_device.evtdev; if (bc) clockevents_shutdown(bc);
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);}
/* * This is called from tick_resume_local() on a resuming CPU. That's * called from the core resume function, tick_unfreeze() and the magic XEN * resume hackery. * * In none of these cases the broadcast device mode can change and the * bit of the resuming CPU in the broadcast mask is safe as well. */bool tick_resume_check_broadcast(void){ if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT) return false; else return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);}
void tick_resume_broadcast(void){ struct clock_event_device *bc; unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
bc = tick_broadcast_device.evtdev;
if (bc) { clockevents_tick_resume(bc);
switch (tick_broadcast_device.mode) { case TICKDEV_MODE_PERIODIC: if (!cpumask_empty(tick_broadcast_mask)) tick_broadcast_start_periodic(bc); break; case TICKDEV_MODE_ONESHOT: if (!cpumask_empty(tick_broadcast_mask)) tick_resume_broadcast_oneshot(bc); break; } } raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);}
#ifdef CONFIG_TICK_ONESHOT
static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
/* * Exposed for debugging: see timer_list.c */struct cpumask *tick_get_broadcast_oneshot_mask(void){ return tick_broadcast_oneshot_mask;}
/* * Called before going idle with interrupts disabled. Checks whether a * broadcast event from the other core is about to happen. We detected * that in tick_broadcast_oneshot_control(). The callsite can use this * to avoid a deep idle transition as we are about to get the * broadcast IPI right away. */noinstr int tick_check_broadcast_expired(void){#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));#else return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);#endif}
/* * Set broadcast interrupt affinity */static void tick_broadcast_set_affinity(struct clock_event_device *bc, const struct cpumask *cpumask){ if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ)) return;
if (cpumask_equal(bc->cpumask, cpumask)) return;
bc->cpumask = cpumask; irq_set_affinity(bc->irq, bc->cpumask);}
static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu, ktime_t expires){ if (!clockevent_state_oneshot(bc)) clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
clockevents_program_event(bc, expires, 1); tick_broadcast_set_affinity(bc, cpumask_of(cpu));}
static void tick_resume_broadcast_oneshot(struct clock_event_device *bc){ clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);}
/* * Called from irq_enter() when idle was interrupted to reenable the * per cpu device. */void tick_check_oneshot_broadcast_this_cpu(void){ if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) { struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
/* * We might be in the middle of switching over from * periodic to oneshot. If the CPU has not yet * switched over, leave the device alone. */ if (td->mode == TICKDEV_MODE_ONESHOT) { clockevents_switch_state(td->evtdev, CLOCK_EVT_STATE_ONESHOT); } }}
/* * 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; tick_broadcast_device.evtdev->next_event_forced = 0; 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); }}
static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu){ if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER)) return 0; if (bc->next_event == KTIME_MAX) return 0; return bc->bound_on == cpu ? -EBUSY : 0;}
static void broadcast_shutdown_local(struct clock_event_device *bc, struct clock_event_device *dev){ /* * For hrtimer based broadcasting we cannot shutdown the cpu * local device if our own event is the first one to expire or * if we own the broadcast timer. */ if (bc->features & CLOCK_EVT_FEAT_HRTIMER) { if (broadcast_needs_cpu(bc, smp_processor_id())) return; if (dev->next_event < bc->next_event) return; } clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);}
static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state, struct tick_device *td, int cpu){ struct clock_event_device *bc, *dev = td->evtdev; int ret = 0; ktime_t now;
raw_spin_lock(&tick_broadcast_lock); bc = tick_broadcast_device.evtdev;
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 no 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 therefore 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;}
static int tick_oneshot_wakeup_control(enum tick_broadcast_state state, struct tick_device *td, int cpu){ struct clock_event_device *dev, *wd;
dev = td->evtdev; if (td->mode != TICKDEV_MODE_ONESHOT) return -EINVAL;
wd = tick_get_oneshot_wakeup_device(cpu); if (!wd) return -ENODEV;
switch (state) { case TICK_BROADCAST_ENTER: clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED); clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT); clockevents_program_event(wd, dev->next_event, 1); break; case TICK_BROADCAST_EXIT: /* We may have transitioned to oneshot mode while idle */ if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT) return -ENODEV; }
return 0;}
int __tick_broadcast_oneshot_control(enum tick_broadcast_state state){ struct tick_device *td = this_cpu_ptr(&tick_cpu_device); int cpu = smp_processor_id();
if (!tick_oneshot_wakeup_control(state, td, cpu)) return 0;
if (tick_broadcast_device.evtdev) return ___tick_broadcast_oneshot_control(state, td, cpu);
/* * If there is no broadcast or wakeup device, tell the caller not * to go into deep idle. */ return -EBUSY;}
/* * Reset the one shot broadcast for a cpu * * Called with tick_broadcast_lock held */static void tick_broadcast_clear_oneshot(int cpu){ cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask); cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);}
static void tick_broadcast_init_next_event(struct cpumask *mask, ktime_t expires){ struct tick_device *td; int cpu;
for_each_cpu(cpu, mask) { td = &per_cpu(tick_cpu_device, cpu); if (td->evtdev) td->evtdev->next_event = expires; }}
static inline ktime_t tick_get_next_period(void){ ktime_t next;
/* * Protect against concurrent updates (store /load tearing on * 32bit). It does not matter if the time is already in the * past. The broadcast device which is about to be programmed will * fire in any case. */ raw_spin_lock(&jiffies_lock); next = tick_next_period; raw_spin_unlock(&jiffies_lock); return next;}
/** * tick_broadcast_setup_oneshot - setup the broadcast device * @bc: the broadcast device * @from_periodic: true if called from periodic mode */static void tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic){ int cpu = smp_processor_id(); ktime_t nexttick = 0;
if (!bc) return;
/* * When the broadcast device was switched to oneshot by the first * CPU handling the NOHZ change, the other CPUs will reach this * code via hrtimer_run_queues() -> tick_check_oneshot_change() * too. Set up the broadcast device only once! */ if (bc->event_handler == tick_handle_oneshot_broadcast) { /* * The CPU which switched from periodic to oneshot mode * set the broadcast oneshot bit for all other CPUs which * are in the general (periodic) broadcast mask to ensure * that CPUs which wait for the periodic broadcast are * woken up. * * Clear the bit for the local CPU as the set bit would * prevent the first tick_broadcast_enter() after this CPU * switched to oneshot state to program the broadcast * device. * * This code can also be reached via tick_broadcast_control(), * but this cannot avoid the tick_broadcast_clear_oneshot() * as that would break the periodic to oneshot transition of * secondary CPUs. But that's harmless as the below only * clears already cleared bits. */ tick_broadcast_clear_oneshot(cpu); return; }
bc->event_handler = tick_handle_oneshot_broadcast; bc->next_event_forced = 0; bc->next_event = KTIME_MAX;
/* * When the tick mode is switched from periodic to oneshot it must * be ensured that CPUs which are waiting for periodic broadcast * get their wake-up at the next tick. This is achieved by ORing * tick_broadcast_mask into tick_broadcast_oneshot_mask. * * For other callers, e.g. broadcast device replacement, * tick_broadcast_oneshot_mask must not be touched as this would * set bits for CPUs which are already NOHZ, but not idle. Their * next tick_broadcast_enter() would observe the bit set and fail * to update the expiry time and the broadcast event device. */ if (from_periodic) { cpumask_copy(tmpmask, tick_broadcast_mask); /* Remove the local CPU as it is obviously not idle */ cpumask_clear_cpu(cpu, tmpmask); cpumask_or(tick_broadcast_oneshot_mask, tick_broadcast_oneshot_mask, tmpmask);
/* * Ensure that the oneshot broadcast handler will wake the * CPUs which are still waiting for periodic broadcast. */ nexttick = tick_get_next_period(); tick_broadcast_init_next_event(tmpmask, nexttick);
/* * If the underlying broadcast clock event device is * already in oneshot state, then there is nothing to do. * The device was already armed for the next tick * in tick_handle_broadcast_periodic() */ if (clockevent_state_oneshot(bc)) return; }
/* * When switching from periodic to oneshot mode arm the broadcast * device for the next tick. * * If the broadcast device has been replaced in oneshot mode and * the oneshot broadcast mask is not empty, then arm it to expire * immediately in order to reevaluate the next expiring timer. * @nexttick is 0 and therefore in the past which will cause the * clockevent code to force an event. * * For both cases the programming can be avoided when the oneshot * broadcast mask is empty. * * tick_broadcast_set_event() implicitly switches the broadcast * device to oneshot state. */ if (!cpumask_empty(tick_broadcast_oneshot_mask)) tick_broadcast_set_event(bc, cpu, nexttick);}
/* * Select oneshot operating mode for the broadcast device */void tick_broadcast_switch_to_oneshot(void){ struct clock_event_device *bc; enum tick_device_mode oldmode; unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
oldmode = tick_broadcast_device.mode; tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT; bc = tick_broadcast_device.evtdev; if (bc) tick_broadcast_setup_oneshot(bc, oldmode == TICKDEV_MODE_PERIODIC);
raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);}
#ifdef CONFIG_HOTPLUG_CPUvoid hotplug_cpu__broadcast_tick_pull(int deadcpu){ struct clock_event_device *bc; unsigned long flags;
raw_spin_lock_irqsave(&tick_broadcast_lock, flags); bc = tick_broadcast_device.evtdev;
if (bc && broadcast_needs_cpu(bc, deadcpu)) { /* * If the broadcast force bit of the current CPU is set, * then the current CPU has not yet reprogrammed the local * timer device to avoid a ping-pong race. See * ___tick_broadcast_oneshot_control(). * * If the broadcast device is hrtimer based then * programming the broadcast event below does not have any * effect because the local clockevent device is not * running and not programmed because the broadcast event * is not earlier than the pending event of the local clock * event device. As a consequence all CPUs waiting for a * broadcast event are stuck forever. * * Detect this condition and reprogram the cpu local timer * device to avoid the starvation. */ if (tick_check_broadcast_expired()) { struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
cpumask_clear_cpu(smp_processor_id(), tick_broadcast_force_mask); tick_program_event(td->evtdev->next_event, 1); }
/* This moves the broadcast assignment to this CPU: */ bc->next_event_forced = 0; clockevents_program_event(bc, bc->next_event, 1); } raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);}
/* * Remove a dying CPU from broadcasting */static void tick_broadcast_oneshot_offline(unsigned int cpu){ if (tick_get_oneshot_wakeup_device(cpu)) tick_set_oneshot_wakeup_device(NULL, cpu);
/* * Clear the broadcast masks for the dead cpu, but do not stop * the broadcast device! */ cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask); cpumask_clear_cpu(cpu, tick_broadcast_pending_mask); cpumask_clear_cpu(cpu, tick_broadcast_force_mask);}#endif
/* * Check, whether the broadcast device is in one shot mode */int tick_broadcast_oneshot_active(void){ return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;}
/* * Check whether the broadcast device supports oneshot. */bool tick_broadcast_oneshot_available(void){ struct clock_event_device *bc = tick_broadcast_device.evtdev;
return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;}
#elseint __tick_broadcast_oneshot_control(enum tick_broadcast_state state){ struct clock_event_device *bc = tick_broadcast_device.evtdev;
if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER)) return -EBUSY;
return 0;}#endif
void __init tick_broadcast_init(void){ zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT); zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT); zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);#ifdef CONFIG_TICK_ONESHOT zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT); zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT); zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);#endif}