linux-kernel - Re: [PATCH 1/3] kernel/sched: introduce vcpu preempted check interface

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Date:	Mon, 27 Jun 2016 22:05:40 +0800
From:	Boqun Feng <boqun.feng@...il.com>
To:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com, peterz@...radead.org, mingo@...hat.com,
	mpe@...erman.id.au, paulus@...ba.org, benh@...nel.crashing.org,
	Waiman.Long@....com, will.deacon@....com, dave@...olabs.net
Subject: Re: [PATCH 1/3] kernel/sched: introduce vcpu preempted check
 interface

On Mon, Jun 27, 2016 at 01:41:28PM -0400, Pan Xinhui wrote:
> this supports to fix lock holder preempted issue which run as a guest
> 
> for kernel users, we could use bool vcpu_is_preempted(int cpu) to detech
> if one vcpu is preempted or not.
> 
> The default implementation is a macrodefined by false. So compiler can
> wrap it out if arch dose not support such vcpu pteempted check.
> 
> archs can implement it by define arch_vcpu_is_preempted().
> 
> Signed-off-by: Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>
> ---
>  include/linux/sched.h | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 6e42ada..dc0a9c3 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -3293,6 +3293,15 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu)
>  
>  #endif /* CONFIG_SMP */
>  
> +#ifdef arch_vcpu_is_preempted
> +static inline bool vcpu_is_preempted(int cpu)
> +{
> +	return arch_vcpu_is_preempted(cpu);
> +}
> +#else
> +#define vcpu_is_preempted(cpu)	false
> +#endif
> +

I think you are missing Peter's comment here. We can

#ifndef vcpu_is_preempted
#define vcpu_is_preempted(cpu)	fasle
#endif

And different archs implement their own versions of vcpu_is_preempted(),
IOW, no need for an arch_vcpu_is_preempted().

Regards,
Boqun

>  extern long sched_setaffinity(pid_t pid, const struct cpumask *new_mask);
>  extern long sched_getaffinity(pid_t pid, struct cpumask *mask);
>  
> -- 
> 2.4.11
> 

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