Re: [Xen-devel] [PATCH v2 5/6] virt, sched: add cpu pinning to smp_call_sync_on_phys_cpu()

From	Juergen Gross <jgross@suse.com>
Newsgroups	linux.kernel
Subject	Re: [Xen-devel] [PATCH v2 5/6] virt, sched: add cpu pinning to smp_call_sync_on_phys_cpu()
Date	2016-03-21 15:30 +0100
Message-ID	<rf90d-6WY-3@gated-at.bofh.it> (permalink)
References	<rf785-5yn-5@gated-at.bofh.it> <rf788-5yn-57@gated-at.bofh.it> <rf90d-6WY-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 21/03/16 14:42, Jan Beulich wrote:
>>>> On 21.03.16 at 13:24, <JGross@suse.com> wrote:
>> @@ -758,9 +759,14 @@ struct smp_sync_call_struct {
>>  static void smp_call_sync_callback(struct work_struct *work)
>>  {
>>  	struct smp_sync_call_struct *sscs;
>> +	unsigned int cpu = smp_processor_id();
> 
> So this obtains the vCPU number, yet ...
> 
>>  	sscs = container_of(work, struct smp_sync_call_struct, work);
>> +	preempt_disable();
>> +	hypervisor_pin_vcpu(cpu);
> 
> ... here you're supposed to pass a pCPU number.
> 
> Also don't you need to call smp_processor_id() after preempt_disable()?

No, I'm running on the workqueue bound to the specific (v)cpu and I'm
expecting this vcpu to be pinned to the same numbered pcpu.

preempt_disable() is just called to avoid scheduling of another thread
while the override pinning is active.


Juergen

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[PATCH v2 0/6]  Support calling functions on dedicated physical cpu Juergen Gross <jgross@suse.com> - 2016-03-21 13:30 +0100
  [PATCH v2 1/6] xen: sync xen header Juergen Gross <jgross@suse.com> - 2016-03-21 13:30 +0100
  [PATCH v2 5/6] virt, sched: add cpu pinning to smp_call_sync_on_phys_cpu() Juergen Gross <jgross@suse.com> - 2016-03-21 13:30 +0100
    Re: [Xen-devel] [PATCH v2 5/6] virt, sched: add cpu pinning to  smp_call_sync_on_phys_cpu() "Jan Beulich" <JBeulich@suse.com> - 2016-03-21 14:50 +0100
      Re: [Xen-devel] [PATCH v2 5/6] virt, sched: add cpu pinning to  smp_call_sync_on_phys_cpu() David Vrabel <david.vrabel@citrix.com> - 2016-03-21 15:20 +0100
    Re: [Xen-devel] [PATCH v2 5/6] virt, sched: add cpu pinning to  smp_call_sync_on_phys_cpu() Juergen Gross <jgross@suse.com> - 2016-03-21 15:30 +0100

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