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linux-sg2042
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Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-hrt 

* 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/tglx/linux-2.6-hrt:
  NOHZ: reevaluate idle sleep length after add_timer_on()
  clocksource: revert: use init_timer_deferrable for clocksource_watchdog
This commit is contained in:
Linus Torvalds 2008-03-26 11:29:35 -07:00
parent 729eb528c7 06d8308c61
commit 8f404faa72
4 changed files with 59 additions and 2 deletions
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6
include/linux/sched.h
View File

@ -1541,6 +1541,12 @@ static inline void idle_task_exit(void) {}
extern void sched_idle_next(void);
#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
extern void wake_up_idle_cpu(int cpu);
#else
static inline void wake_up_idle_cpu(int cpu) { }
#endif
#ifdef CONFIG_SCHED_DEBUG
extern unsigned int sysctl_sched_latency;
extern unsigned int sysctl_sched_min_granularity;

43
kernel/sched.c
View File

@ -1052,6 +1052,49 @@ static void resched_cpu(int cpu)
resched_task(cpu_curr(cpu));
spin_unlock_irqrestore(&rq->lock, flags);
}
#ifdef CONFIG_NO_HZ
/*
* When add_timer_on() enqueues a timer into the timer wheel of an
* idle CPU then this timer might expire before the next timer event
* which is scheduled to wake up that CPU. In case of a completely
* idle system the next event might even be infinite time into the
* future. wake_up_idle_cpu() ensures that the CPU is woken up and
* leaves the inner idle loop so the newly added timer is taken into
* account when the CPU goes back to idle and evaluates the timer
* wheel for the next timer event.
*/
void wake_up_idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
if (cpu == smp_processor_id())
return;
/*
* This is safe, as this function is called with the timer
* wheel base lock of (cpu) held. When the CPU is on the way
* to idle and has not yet set rq->curr to idle then it will
* be serialized on the timer wheel base lock and take the new
* timer into account automatically.
*/
if (rq->curr != rq->idle)
return;
/*
* We can set TIF_RESCHED on the idle task of the other CPU
* lockless. The worst case is that the other CPU runs the
* idle task through an additional NOOP schedule()
*/
set_tsk_thread_flag(rq->idle, TIF_NEED_RESCHED);
/* NEED_RESCHED must be visible before we test polling */
smp_mb();
if (!tsk_is_polling(rq->idle))
smp_send_reschedule(cpu);
}
#endif
#else
static void __resched_task(struct task_struct *p, int tif_bit)
{

2
kernel/time/clocksource.c
View File

@ -174,7 +174,7 @@ static void clocksource_check_watchdog(struct clocksource *cs)
if (watchdog)
del_timer(&watchdog_timer);
watchdog = cs;
init_timer_deferrable(&watchdog_timer);
init_timer(&watchdog_timer);
watchdog_timer.function = clocksource_watchdog;
/* Reset watchdog cycles */

10
kernel/timer.c
View File

@ -451,10 +451,18 @@ void add_timer_on(struct timer_list *timer, int cpu)
spin_lock_irqsave(&base->lock, flags);
timer_set_base(timer, base);
internal_add_timer(base, timer);
/*
* Check whether the other CPU is idle and needs to be
* triggered to reevaluate the timer wheel when nohz is
* active. We are protected against the other CPU fiddling
* with the timer by holding the timer base lock. This also
* makes sure that a CPU on the way to idle can not evaluate
* the timer wheel.
*/
wake_up_idle_cpu(cpu);
spin_unlock_irqrestore(&base->lock, flags);
}
/**
* mod_timer - modify a timer's timeout
* @timer: the timer to be modified