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SubjectRe: 2.6.25-rc5-git6: Reported regressions from 2.6.24
Gabriel C wrote:
> Thomas Gleixner wrote:
>> On Sat, 22 Mar 2008, Thomas Gleixner wrote:
>>> On Sat, 22 Mar 2008, Gabriel C wrote:
>>>> With this one TSC is fine but now I get a warning on boot :
>>> Good. It confirms my assumptions about the root cause.
>>>
>>>> [ 0.041037] ------------[ cut here ]------------
>>>> [ 0.041052] WARNING: at arch/x86/kernel/smp_32.c:562 native_smp_call_function_mask+0x23/0x11e()
>>> Grr. I'll work out a solution for that one.
>> Gabriel,
>>
>> I'm happy to rack your nerves some more.
>
> No worries :)
>
>> After discussing the issue with Peter and Ingo the following solution
>> seems to be the one which is the least intrusive.
>>
>> Can you please give it a test ride ?
>
> Done , git head + Andi's patch + this version of your patch does work here.
>
> Also time-warp-test is just fine and everything else seems to work.

Also I've tested with my other motherboard and is fine too :)

Feel free to add my Tested-by when you push this patch.

>
>
>> ---
>> include/linux/sched.h | 6 ++++++
>> kernel/sched.c | 42 ++++++++++++++++++++++++++++++++++++++++++
>> kernel/timer.c | 10 +++++++++-
>> 3 files changed, 57 insertions(+), 1 deletion(-)
>>
>> Index: linux-2.6/include/linux/sched.h
>> ===================================================================
>> --- linux-2.6.orig/include/linux/sched.h
>> +++ linux-2.6/include/linux/sched.h
>> @@ -1541,6 +1541,12 @@ static inline void idle_task_exit(void)
>>
>> extern void sched_idle_next(void);
>>
>> +#ifdef CONFIG_NO_HZ
>> +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;
>> Index: linux-2.6/kernel/sched.c
>> ===================================================================
>> --- linux-2.6.orig/kernel/sched.c
>> +++ linux-2.6/kernel/sched.c
>> @@ -848,6 +848,48 @@ static inline void resched_task(struct t
>> __resched_task(p, TIF_NEED_RESCHED);
>> }
>>
>> +#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 newle 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
>> +
>> #ifdef CONFIG_SCHED_HRTICK
>> /*
>> * Use HR-timers to deliver accurate preemption points.
>> Index: linux-2.6/kernel/timer.c
>> ===================================================================
>> --- linux-2.6.orig/kernel/timer.c
>> +++ linux-2.6/kernel/timer.c
>> @@ -451,10 +451,18 @@ void add_timer_on(struct timer_list *tim
>> 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
>


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