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SubjectRe: idle issues running sembench on 128 cpus II
On 05/04/2011 06:48 PM, Andi Kleen wrote:
>> Here's a new patch without the raw. Boots on my Westmere.
>
> Sorry appended the old patch. Here's really the new version.
>
> From: Andi Kleen<ak@linux.intel.com>
> Date: Wed, 4 May 2011 15:09:27 -0700
> Subject: [PATCH] Move C3 stop test outside lock
>
> Avoid taking locks in the idle path for systems where the timer
> doesn't stop in C3.
>
> Signed-off-by: Andi Kleen<ak@linux.intel.com>
>
> diff --git a/kernel/time/tick-broadcast.c b/kernel/time/tick-broadcast.c
> index da800ff..7f565b7 100644
> --- a/kernel/time/tick-broadcast.c
> +++ b/kernel/time/tick-broadcast.c
> @@ -456,23 +456,22 @@ void tick_broadcast_oneshot_control(unsigned long reason)
> unsigned long flags;
> int cpu;
>
> - raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
> -
> /*
> * Periodic mode does not care about the enter/exit of power
> * states
> */
> if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
> - goto out;
> + return;
>
> - bc = tick_broadcast_device.evtdev;
> cpu = smp_processor_id();
> + bc = tick_broadcast_device.evtdev;
> td =&per_cpu(tick_cpu_device, cpu);
> dev = td->evtdev;
>
> if (!(dev->features& CLOCK_EVT_FEAT_C3STOP))
> - goto out;
> + return;

out: is now defined but not used in this function.

>
> + raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
> if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
> if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
> cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());
>


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