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

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Message-Id: <20160628070013.GC3784@osiris>
Date:	Tue, 28 Jun 2016 09:00:13 +0200
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Pan Xinhui <xinhui.pan@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com, mingo@...hat.com, mpe@...erman.id.au,
	paulus@...ba.org, benh@...nel.crashing.org, Waiman.Long@....com,
	boqun.feng@...il.com, will.deacon@....com, dave@...olabs.net,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: [PATCH 1/3] kernel/sched: introduce vcpu preempted check
 interface

On Mon, Jun 27, 2016 at 04:00:43PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 27, 2016 at 01:41:28PM -0400, Pan Xinhui wrote:
> > +++ 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
> 
> #ifndef vcpu_is_preempted
> #define vcpu_is_preempted(cpu)		(false)
> #endif
> 
> Is so much simpler...
> 
> Also, please Cc the virt list so that other interested parties can
> comment, and maybe also the s390 folks.

The s390 implementation would be to simply use cpu_is_preempted() from
arch/s390/lib/spinlock.c.
It's nice that there will be a common code function for this!