[PATCH] s390x/spinlock: Provide vcpu_is_preempted globally

[PATCH] s390x/spinlock: Provide vcpu_is_preempted globally

[Christian Borntraeger]

this implements the s390 backend for commit
"kernel/sched: introduce vcpu preempted check interface"
by simply reusing the existing cpu_is_preempted function.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
Martin, Heiko,

this patch is a minimal change by not touching all existing users of
cpu_is_preempted in spinlock.c. If you want it differently, let me
know.


 arch/s390/include/asm/spinlock.h | 7 +++++++
 arch/s390/lib/spinlock.c         | 3 ++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 63ebf37..6e82986 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -21,6 +21,13 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
 	return __sync_bool_compare_and_swap(lock, old, new);
 }
 
+int arch_vcpu_is_preempted(int cpu);
+#define vcpu_is_preempted cpu_is_preempted
+static inline bool cpu_is_preempted(int cpu)
+{
+	return arch_vcpu_is_preempted(cpu);
+}
+
 /*
  * Simple spin lock operations.  There are two variants, one clears IRQ's
  * on the local processor, one does not.
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index e5f50a7..9f473c8 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -37,7 +37,7 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
 	asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
 }
 
-static inline int cpu_is_preempted(int cpu)
+int arch_vcpu_is_preempted(int cpu)
 {
 	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
 		return 0;
@@ -45,6 +45,7 @@ static inline int cpu_is_preempted(int cpu)
 		return 0;
 	return 1;
 }
+EXPORT_SYMBOL(arch_vcpu_is_preempted);
 
 void arch_spin_lock_wait(arch_spinlock_t *lp)
 {
-- 
2.5.5

Re: [PATCH] s390x/spinlock: Provide vcpu_is_preempted globally

[Martin Schwidefsky]

On Thu, 29 Sep 2016 13:54:16 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> this implements the s390 backend for commit
> "kernel/sched: introduce vcpu preempted check interface"
> by simply reusing the existing cpu_is_preempted function.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---
> Martin, Heiko,
> 
> this patch is a minimal change by not touching all existing users of
> cpu_is_preempted in spinlock.c. If you want it differently, let me
> know.
> 
> 
>  arch/s390/include/asm/spinlock.h | 7 +++++++
>  arch/s390/lib/spinlock.c         | 3 ++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
> index 63ebf37..6e82986 100644
> --- a/arch/s390/include/asm/spinlock.h
> +++ b/arch/s390/include/asm/spinlock.h
> @@ -21,6 +21,13 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
>  	return __sync_bool_compare_and_swap(lock, old, new);
>  }
> 
> +int arch_vcpu_is_preempted(int cpu);
> +#define vcpu_is_preempted cpu_is_preempted
> +static inline bool cpu_is_preempted(int cpu)
> +{
> +	return arch_vcpu_is_preempted(cpu);
> +}
> +
>  /*
>   * Simple spin lock operations.  There are two variants, one clears IRQ's
>   * on the local processor, one does not.
> diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
> index e5f50a7..9f473c8 100644
> --- a/arch/s390/lib/spinlock.c
> +++ b/arch/s390/lib/spinlock.c
> @@ -37,7 +37,7 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
>  	asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
>  }
> 
> -static inline int cpu_is_preempted(int cpu)
> +int arch_vcpu_is_preempted(int cpu)
>  {
>  	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
>  		return 0;
> @@ -45,6 +45,7 @@ static inline int cpu_is_preempted(int cpu)
>  		return 0;
>  	return 1;
>  }
> +EXPORT_SYMBOL(arch_vcpu_is_preempted);
> 
>  void arch_spin_lock_wait(arch_spinlock_t *lp)
>  {

Hmm, if I look at the code we now have an additional function for
the spinlock loops. The call arch_vcpu_is_preempted which test
CIF_ENABLED_WAIT and then calls smp_vcpu_scheduled(). The test
used to be inline.

A better solution would be to move the CIF_ENABLED_WAIT test to the
smp_vcpu_scheduled() function, rename it to arch_vcpu_is_preempted()
and then export that function. The cpu_is_preempted() function is
replaced by arch_vcpu_is_preempted() which does make a lot of sense,
no?

-- 
blue skies,
   Martin.

"Reality continues to ruin my life." - Calvin.

Re: [PATCH] s390x/spinlock: Provide vcpu_is_preempted globally

[Christian Borntraeger]

On 09/29/2016 03:11 PM, Martin Schwidefsky wrote:
> On Thu, 29 Sep 2016 13:54:16 +0200
> Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> 
>> this implements the s390 backend for commit
>> "kernel/sched: introduce vcpu preempted check interface"
>> by simply reusing the existing cpu_is_preempted function.
>>
>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>> ---
>> Martin, Heiko,
>>
>> this patch is a minimal change by not touching all existing users of
>> cpu_is_preempted in spinlock.c. If you want it differently, let me
>> know.
>>
>>
>>  arch/s390/include/asm/spinlock.h | 7 +++++++
>>  arch/s390/lib/spinlock.c         | 3 ++-
>>  2 files changed, 9 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
>> index 63ebf37..6e82986 100644
>> --- a/arch/s390/include/asm/spinlock.h
>> +++ b/arch/s390/include/asm/spinlock.h
>> @@ -21,6 +21,13 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
>>  	return __sync_bool_compare_and_swap(lock, old, new);
>>  }
>>
>> +int arch_vcpu_is_preempted(int cpu);
>> +#define vcpu_is_preempted cpu_is_preempted
>> +static inline bool cpu_is_preempted(int cpu)
>> +{
>> +	return arch_vcpu_is_preempted(cpu);
>> +}
>> +
>>  /*
>>   * Simple spin lock operations.  There are two variants, one clears IRQ's
>>   * on the local processor, one does not.
>> diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
>> index e5f50a7..9f473c8 100644
>> --- a/arch/s390/lib/spinlock.c
>> +++ b/arch/s390/lib/spinlock.c
>> @@ -37,7 +37,7 @@ static inline void _raw_compare_and_delay(unsigned int *lock, unsigned int old)
>>  	asm(".insn rsy,0xeb0000000022,%0,0,%1" : : "d" (old), "Q" (*lock));
>>  }
>>
>> -static inline int cpu_is_preempted(int cpu)
>> +int arch_vcpu_is_preempted(int cpu)
>>  {
>>  	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
>>  		return 0;
>> @@ -45,6 +45,7 @@ static inline int cpu_is_preempted(int cpu)
>>  		return 0;
>>  	return 1;
>>  }
>> +EXPORT_SYMBOL(arch_vcpu_is_preempted);
>>
>>  void arch_spin_lock_wait(arch_spinlock_t *lp)
>>  {
> 
> Hmm, if I look at the code we now have an additional function for
> the spinlock loops. The call arch_vcpu_is_preempted which test
> CIF_ENABLED_WAIT and then calls smp_vcpu_scheduled(). The test
> used to be inline.
> 
> A better solution would be to move the CIF_ENABLED_WAIT test to the
> smp_vcpu_scheduled() function, rename it to arch_vcpu_is_preempted()
> and then export that function.
 The cpu_is_preempted() function is
> replaced by arch_vcpu_is_preempted() which does make a lot of sense,
> no?
> 

Yes that makes sense, will spin a v2.