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![Suresh Siddha](/assets/img/avatar_default.png)
Currently clockevents_notify() is called with interrupts enabled at some places and interrupts disabled at some other places. This results in a deadlock in this scenario. cpu A holds clockevents_lock in clockevents_notify() with irqs enabled cpu B waits for clockevents_lock in clockevents_notify() with irqs disabled cpu C doing set_mtrr() which will try to rendezvous of all the cpus. This will result in C and A come to the rendezvous point and waiting for B. B is stuck forever waiting for the spinlock and thus not reaching the rendezvous point. Fix the clockevents code so that clockevents_lock is taken with interrupts disabled and thus avoid the above deadlock. Also call lapic_timer_propagate_broadcast() on the destination cpu so that we avoid calling smp_call_function() in the clockevents notifier chain. This issue left us wondering if we need to change the MTRR rendezvous logic to use stop machine logic (instead of smp_call_function) or add a check in spinlock debug code to see if there are other spinlocks which gets taken under both interrupts enabled/disabled conditions. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Cc: "Pallipadi Venkatesh" <venkatesh.pallipadi@intel.com> Cc: "Brown Len" <len.brown@intel.com> LKML-Reference: <1250544899.2709.210.camel@sbs-t61.sc.intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
261 lines
6.1 KiB
C
261 lines
6.1 KiB
C
/*
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* linux/kernel/time/clockevents.c
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*
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* This file contains functions which manage clock event devices.
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*
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* Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
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* Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
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* Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
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*
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* This code is licenced under the GPL version 2. For details see
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* kernel-base/COPYING.
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*/
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#include <linux/clockchips.h>
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#include <linux/hrtimer.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/notifier.h>
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#include <linux/smp.h>
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#include <linux/sysdev.h>
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#include <linux/tick.h>
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/* The registered clock event devices */
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static LIST_HEAD(clockevent_devices);
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static LIST_HEAD(clockevents_released);
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/* Notification for clock events */
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static RAW_NOTIFIER_HEAD(clockevents_chain);
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/* Protection for the above */
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static DEFINE_SPINLOCK(clockevents_lock);
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/**
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* clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
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* @latch: value to convert
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* @evt: pointer to clock event device descriptor
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*
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* Math helper, returns latch value converted to nanoseconds (bound checked)
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*/
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unsigned long clockevent_delta2ns(unsigned long latch,
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struct clock_event_device *evt)
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{
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u64 clc = ((u64) latch << evt->shift);
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if (unlikely(!evt->mult)) {
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evt->mult = 1;
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WARN_ON(1);
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}
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do_div(clc, evt->mult);
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if (clc < 1000)
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clc = 1000;
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if (clc > LONG_MAX)
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clc = LONG_MAX;
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return (unsigned long) clc;
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}
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EXPORT_SYMBOL_GPL(clockevent_delta2ns);
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/**
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* clockevents_set_mode - set the operating mode of a clock event device
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* @dev: device to modify
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* @mode: new mode
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*
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* Must be called with interrupts disabled !
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*/
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void clockevents_set_mode(struct clock_event_device *dev,
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enum clock_event_mode mode)
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{
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if (dev->mode != mode) {
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dev->set_mode(mode, dev);
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dev->mode = mode;
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/*
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* A nsec2cyc multiplicator of 0 is invalid and we'd crash
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* on it, so fix it up and emit a warning:
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*/
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if (mode == CLOCK_EVT_MODE_ONESHOT) {
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if (unlikely(!dev->mult)) {
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dev->mult = 1;
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WARN_ON(1);
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}
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}
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}
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}
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/**
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* clockevents_shutdown - shutdown the device and clear next_event
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* @dev: device to shutdown
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*/
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void clockevents_shutdown(struct clock_event_device *dev)
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{
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clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
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dev->next_event.tv64 = KTIME_MAX;
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}
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/**
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* clockevents_program_event - Reprogram the clock event device.
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* @expires: absolute expiry time (monotonic clock)
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*
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* Returns 0 on success, -ETIME when the event is in the past.
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*/
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int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
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ktime_t now)
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{
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unsigned long long clc;
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int64_t delta;
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if (unlikely(expires.tv64 < 0)) {
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WARN_ON_ONCE(1);
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return -ETIME;
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}
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delta = ktime_to_ns(ktime_sub(expires, now));
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if (delta <= 0)
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return -ETIME;
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dev->next_event = expires;
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if (dev->mode == CLOCK_EVT_MODE_SHUTDOWN)
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return 0;
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if (delta > dev->max_delta_ns)
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delta = dev->max_delta_ns;
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if (delta < dev->min_delta_ns)
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delta = dev->min_delta_ns;
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clc = delta * dev->mult;
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clc >>= dev->shift;
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return dev->set_next_event((unsigned long) clc, dev);
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}
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/**
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* clockevents_register_notifier - register a clock events change listener
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*/
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int clockevents_register_notifier(struct notifier_block *nb)
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{
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unsigned long flags;
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int ret;
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spin_lock_irqsave(&clockevents_lock, flags);
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ret = raw_notifier_chain_register(&clockevents_chain, nb);
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spin_unlock_irqrestore(&clockevents_lock, flags);
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return ret;
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}
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/*
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* Notify about a clock event change. Called with clockevents_lock
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* held.
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*/
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static void clockevents_do_notify(unsigned long reason, void *dev)
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{
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raw_notifier_call_chain(&clockevents_chain, reason, dev);
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}
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/*
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* Called after a notify add to make devices available which were
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* released from the notifier call.
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*/
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static void clockevents_notify_released(void)
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{
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struct clock_event_device *dev;
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while (!list_empty(&clockevents_released)) {
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dev = list_entry(clockevents_released.next,
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struct clock_event_device, list);
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list_del(&dev->list);
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list_add(&dev->list, &clockevent_devices);
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clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
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}
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}
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/**
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* clockevents_register_device - register a clock event device
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* @dev: device to register
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*/
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void clockevents_register_device(struct clock_event_device *dev)
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{
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unsigned long flags;
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BUG_ON(dev->mode != CLOCK_EVT_MODE_UNUSED);
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BUG_ON(!dev->cpumask);
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spin_lock_irqsave(&clockevents_lock, flags);
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list_add(&dev->list, &clockevent_devices);
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clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
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clockevents_notify_released();
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spin_unlock_irqrestore(&clockevents_lock, flags);
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}
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EXPORT_SYMBOL_GPL(clockevents_register_device);
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/*
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* Noop handler when we shut down an event device
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*/
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void clockevents_handle_noop(struct clock_event_device *dev)
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{
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}
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/**
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* clockevents_exchange_device - release and request clock devices
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* @old: device to release (can be NULL)
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* @new: device to request (can be NULL)
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*
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* Called from the notifier chain. clockevents_lock is held already
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*/
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void clockevents_exchange_device(struct clock_event_device *old,
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struct clock_event_device *new)
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{
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unsigned long flags;
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local_irq_save(flags);
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/*
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* Caller releases a clock event device. We queue it into the
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* released list and do a notify add later.
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*/
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if (old) {
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clockevents_set_mode(old, CLOCK_EVT_MODE_UNUSED);
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list_del(&old->list);
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list_add(&old->list, &clockevents_released);
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}
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if (new) {
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BUG_ON(new->mode != CLOCK_EVT_MODE_UNUSED);
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clockevents_shutdown(new);
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}
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local_irq_restore(flags);
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}
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#ifdef CONFIG_GENERIC_CLOCKEVENTS
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/**
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* clockevents_notify - notification about relevant events
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*/
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void clockevents_notify(unsigned long reason, void *arg)
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{
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struct list_head *node, *tmp;
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unsigned long flags;
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spin_lock_irqsave(&clockevents_lock, flags);
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clockevents_do_notify(reason, arg);
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switch (reason) {
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case CLOCK_EVT_NOTIFY_CPU_DEAD:
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/*
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* Unregister the clock event devices which were
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* released from the users in the notify chain.
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*/
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list_for_each_safe(node, tmp, &clockevents_released)
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list_del(node);
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break;
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default:
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break;
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}
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spin_unlock_irqrestore(&clockevents_lock, flags);
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}
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EXPORT_SYMBOL_GPL(clockevents_notify);
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#endif
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