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

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Message-Id: <5771EBE7.3060201@linux.vnet.ibm.com>
Date:	Tue, 28 Jun 2016 11:15:51 +0800
From:	xinhui <xinhui.pan@...ux.vnet.ibm.com>
To:	Boqun Feng <boqun.feng@...il.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 2016年06月27日 22:05, Boqun Feng wrote:
> 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().
>
yes, right.
just vcpu_is_preempted, no arch_vcpu_is_preempted..
thanks

> 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
>>