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

[xinhui]

On 2016年06月28日 15:00, Heiko Carstens wrote:

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.

that's great.


It's nice that there will be a common code function for this!



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

[Heiko Carstens]

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!

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

[xinhui]

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 
---
  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



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

[xinhui]

On 2016年06月27日 22:02, Peter Zijlstra wrote:

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...


fair enough.


Also, please Cc the virt list so that other interested parties can
comment, and maybe also the s390 folks.



oh. I forgot that. maybe we need cc more.

root@ltcalpine2-lp13:~/linux# find ./arch -name kvm
./arch/arm/kvm
./arch/arm64/kvm
./arch/mips/kvm
./arch/powerpc/kvm
./arch/s390/kvm
./arch/tile/kvm
./arch/x86/kvm


And before you hurry off to post again, add a patch doing
mutex_spin_on_owner() and rwsem_spin_in_owner().


will do that.

thanks for your suggestion. :)

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

[Peter Zijlstra]

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.

And before you hurry off to post again, add a patch doing
mutex_spin_on_owner() and rwsem_spin_in_owner().
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Re: [PATCH 1/3] kernel/sched: introduce vcpu preempted check interface

[Boqun Feng]

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

[Peter Zijlstra]

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.
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