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[PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted

Started byChristian Borntraeger <borntraeger@de.ibm.com>
First post2016-09-29 18:00 +0200
Last post2016-09-30 16:40 +0200
Articles 6 — 3 participants

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  [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted Christian Borntraeger <borntraeger@de.ibm.com> - 2016-09-29 18:00 +0200
    Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted Pan Xinhui <xinhui@linux.vnet.ibm.com> - 2016-09-30 07:00 +0200
      Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted Boqun Feng <boqun.feng@gmail.com> - 2016-09-30 08:00 +0200
        Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted Pan Xinhui <xinhui@linux.vnet.ibm.com> - 2016-09-30 08:40 +0200
          Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted Christian Borntraeger <borntraeger@de.ibm.com> - 2016-10-04 12:20 +0200
      Re: [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted Christian Borntraeger <borntraeger@de.ibm.com> - 2016-09-30 16:40 +0200

#1493542 — [PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted

FromChristian Borntraeger <borntraeger@de.ibm.com>
Date2016-09-29 18:00 +0200
Subject[PATCH v2 1/1] s390/spinlock: Provide vcpu_is_preempted
Message-ID<smLUB-5YJ-15@gated-at.bofh.it>
this implements the s390 backend for commit
"kernel/sched: introduce vcpu preempted check interface"
by reworking the existing smp_vcpu_scheduled into
arch_vcpu_is_preempted. We can then also get rid of the
local cpu_is_preempted function by moving the
CIF_ENABLED_WAIT test into arch_vcpu_is_preempted.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
---
 arch/s390/include/asm/spinlock.h |  3 +++
 arch/s390/kernel/smp.c           |  9 +++++++--
 arch/s390/lib/spinlock.c         | 25 ++++++++-----------------
 3 files changed, 18 insertions(+), 19 deletions(-)

diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
index 63ebf37..e16e02f 100644
--- a/arch/s390/include/asm/spinlock.h
+++ b/arch/s390/include/asm/spinlock.h
@@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
 	return __sync_bool_compare_and_swap(lock, old, new);
 }
 
+bool arch_vcpu_is_preempted(int cpu);
+#define vcpu_is_preempted arch_vcpu_is_preempted
+
 /*
  * Simple spin lock operations.  There are two variants, one clears IRQ's
  * on the local processor, one does not.
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 7b89a75..4aadd16 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address)
 	return -1;
 }
 
-int smp_vcpu_scheduled(int cpu)
+bool arch_vcpu_is_preempted(int cpu)
 {
-	return pcpu_running(pcpu_devices + cpu);
+	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
+		return false;
+	if (pcpu_running(pcpu_devices + cpu))
+		return false;
+	return true;
 }
+EXPORT_SYMBOL(arch_vcpu_is_preempted);
 
 void smp_yield_cpu(int cpu)
 {
diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
index e5f50a7..e48a48e 100644
--- a/arch/s390/lib/spinlock.c
+++ b/arch/s390/lib/spinlock.c
@@ -37,15 +37,6 @@ 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)
-{
-	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
-		return 0;
-	if (smp_vcpu_scheduled(cpu))
-		return 0;
-	return 1;
-}
-
 void arch_spin_lock_wait(arch_spinlock_t *lp)
 {
 	unsigned int cpu = SPINLOCK_LOCKVAL;
@@ -62,7 +53,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
 			continue;
 		}
 		/* First iteration: check if the lock owner is running. */
-		if (first_diag && cpu_is_preempted(~owner)) {
+		if (first_diag && arch_vcpu_is_preempted(~owner)) {
 			smp_yield_cpu(~owner);
 			first_diag = 0;
 			continue;
@@ -81,7 +72,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
 		 * yield the CPU unconditionally. For LPAR rely on the
 		 * sense running status.
 		 */
-		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
+		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
 			smp_yield_cpu(~owner);
 			first_diag = 0;
 		}
@@ -108,7 +99,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
 			continue;
 		}
 		/* Check if the lock owner is running. */
-		if (first_diag && cpu_is_preempted(~owner)) {
+		if (first_diag && arch_vcpu_is_preempted(~owner)) {
 			smp_yield_cpu(~owner);
 			first_diag = 0;
 			continue;
@@ -127,7 +118,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
 		 * yield the CPU unconditionally. For LPAR rely on the
 		 * sense running status.
 		 */
-		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
+		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
 			smp_yield_cpu(~owner);
 			first_diag = 0;
 		}
@@ -165,7 +156,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
 	owner = 0;
 	while (1) {
 		if (count-- <= 0) {
-			if (owner && cpu_is_preempted(~owner))
+			if (owner && arch_vcpu_is_preempted(~owner))
 				smp_yield_cpu(~owner);
 			count = spin_retry;
 		}
@@ -211,7 +202,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
 	owner = 0;
 	while (1) {
 		if (count-- <= 0) {
-			if (owner && cpu_is_preempted(~owner))
+			if (owner && arch_vcpu_is_preempted(~owner))
 				smp_yield_cpu(~owner);
 			count = spin_retry;
 		}
@@ -241,7 +232,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
 	owner = 0;
 	while (1) {
 		if (count-- <= 0) {
-			if (owner && cpu_is_preempted(~owner))
+			if (owner && arch_vcpu_is_preempted(~owner))
 				smp_yield_cpu(~owner);
 			count = spin_retry;
 		}
@@ -285,7 +276,7 @@ void arch_lock_relax(unsigned int cpu)
 {
 	if (!cpu)
 		return;
-	if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu))
+	if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(~cpu))
 		return;
 	smp_yield_cpu(~cpu);
 }
-- 
2.5.5

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#1493881

FromPan Xinhui <xinhui@linux.vnet.ibm.com>
Date2016-09-30 07:00 +0200
Message-ID<smY5r-5Au-3@gated-at.bofh.it>
In reply to#1493542

在 2016/9/29 23:51, Christian Borntraeger 写道:
> this implements the s390 backend for commit
> "kernel/sched: introduce vcpu preempted check interface"
> by reworking the existing smp_vcpu_scheduled into
> arch_vcpu_is_preempted. We can then also get rid of the
> local cpu_is_preempted function by moving the
> CIF_ENABLED_WAIT test into arch_vcpu_is_preempted.
>
> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> ---

hi, Christian
	thanks for your patch!

>  arch/s390/include/asm/spinlock.h |  3 +++
>  arch/s390/kernel/smp.c           |  9 +++++++--
>  arch/s390/lib/spinlock.c         | 25 ++++++++-----------------
>  3 files changed, 18 insertions(+), 19 deletions(-)
>
> diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
> index 63ebf37..e16e02f 100644
> --- a/arch/s390/include/asm/spinlock.h
> +++ b/arch/s390/include/asm/spinlock.h
> @@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
>  	return __sync_bool_compare_and_swap(lock, old, new);
>  }
>
> +bool arch_vcpu_is_preempted(int cpu);
> +#define vcpu_is_preempted arch_vcpu_is_preempted
> +
>  /*
>   * Simple spin lock operations.  There are two variants, one clears IRQ's
>   * on the local processor, one does not.
> diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
> index 7b89a75..4aadd16 100644
> --- a/arch/s390/kernel/smp.c
> +++ b/arch/s390/kernel/smp.c
> @@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address)
>  	return -1;
>  }
>
> -int smp_vcpu_scheduled(int cpu)
  
root@ltcalpine2-lp13:~/linux# git grep -wn smp_vcpu_scheduled arch/s390/
arch/s390/include/asm/smp.h:34:extern int smp_vcpu_scheduled(int cpu);
arch/s390/include/asm/smp.h:56:static inline int smp_vcpu_scheduled(int cpu) { return 1; }
arch/s390/kernel/smp.c:371:int smp_vcpu_scheduled(int cpu)
arch/s390/lib/spinlock.c:44:    if (smp_vcpu_scheduled(cpu))

> +bool arch_vcpu_is_preempted(int cpu)
>  {
> -	return pcpu_running(pcpu_devices + cpu);
> +	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
> +		return false;
> +	if (pcpu_running(pcpu_devices + cpu))
> +		return false;
I saw smp_vcpu_scheduled() returns true always on !SMP system.

maybe we can do somegthing silimar. like below

#ifndef CONFIG_SMP
static inline bool arch_vcpu_is_preempted(int cpu) { return !test_cpu_flag_of(CIF_ENABLED_WAIT, cpu); }
#else
...

but I can't help thinking that if this is a!SMP system, maybe we could only
#ifndef CONFIG_SMP
static inline bool arch_vcpu_is_preempted(int cpu) { return false; }
#else
...


thanks
xinhui

> +	return true;
>  }
> +EXPORT_SYMBOL(arch_vcpu_is_preempted);
>
>  void smp_yield_cpu(int cpu)
>  {
> diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
> index e5f50a7..e48a48e 100644
> --- a/arch/s390/lib/spinlock.c
> +++ b/arch/s390/lib/spinlock.c
> @@ -37,15 +37,6 @@ 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)
> -{
> -	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
> -		return 0;
> -	if (smp_vcpu_scheduled(cpu))
> -		return 0;
> -	return 1;
> -}
> -
>  void arch_spin_lock_wait(arch_spinlock_t *lp)
>  {
>  	unsigned int cpu = SPINLOCK_LOCKVAL;
> @@ -62,7 +53,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
>  			continue;
>  		}
>  		/* First iteration: check if the lock owner is running. */
> -		if (first_diag && cpu_is_preempted(~owner)) {
> +		if (first_diag && arch_vcpu_is_preempted(~owner)) {
>  			smp_yield_cpu(~owner);
>  			first_diag = 0;
>  			continue;
> @@ -81,7 +72,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
>  		 * yield the CPU unconditionally. For LPAR rely on the
>  		 * sense running status.
>  		 */
> -		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
> +		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
>  			smp_yield_cpu(~owner);
>  			first_diag = 0;
>  		}
> @@ -108,7 +99,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
>  			continue;
>  		}
>  		/* Check if the lock owner is running. */
> -		if (first_diag && cpu_is_preempted(~owner)) {
> +		if (first_diag && arch_vcpu_is_preempted(~owner)) {
>  			smp_yield_cpu(~owner);
>  			first_diag = 0;
>  			continue;
> @@ -127,7 +118,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
>  		 * yield the CPU unconditionally. For LPAR rely on the
>  		 * sense running status.
>  		 */
> -		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
> +		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
>  			smp_yield_cpu(~owner);
>  			first_diag = 0;
>  		}
> @@ -165,7 +156,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
>  	owner = 0;
>  	while (1) {
>  		if (count-- <= 0) {
> -			if (owner && cpu_is_preempted(~owner))
> +			if (owner && arch_vcpu_is_preempted(~owner))
>  				smp_yield_cpu(~owner);
>  			count = spin_retry;
>  		}
> @@ -211,7 +202,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
>  	owner = 0;
>  	while (1) {
>  		if (count-- <= 0) {
> -			if (owner && cpu_is_preempted(~owner))
> +			if (owner && arch_vcpu_is_preempted(~owner))
>  				smp_yield_cpu(~owner);
>  			count = spin_retry;
>  		}
> @@ -241,7 +232,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
>  	owner = 0;
>  	while (1) {
>  		if (count-- <= 0) {
> -			if (owner && cpu_is_preempted(~owner))
> +			if (owner && arch_vcpu_is_preempted(~owner))
>  				smp_yield_cpu(~owner);
>  			count = spin_retry;
>  		}
> @@ -285,7 +276,7 @@ void arch_lock_relax(unsigned int cpu)
>  {
>  	if (!cpu)
>  		return;
> -	if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu))
> +	if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(~cpu))
>  		return;
>  	smp_yield_cpu(~cpu);
>  }
>

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#1493893

FromBoqun Feng <boqun.feng@gmail.com>
Date2016-09-30 08:00 +0200
Message-ID<smZ1v-6b5-1@gated-at.bofh.it>
In reply to#1493881

[Multipart message — attachments visible in raw view] — view raw

On Fri, Sep 30, 2016 at 12:49:52PM +0800, Pan Xinhui wrote:
> 
> 
> 在 2016/9/29 23:51, Christian Borntraeger 写道:
> > this implements the s390 backend for commit
> > "kernel/sched: introduce vcpu preempted check interface"
> > by reworking the existing smp_vcpu_scheduled into
> > arch_vcpu_is_preempted. We can then also get rid of the
> > local cpu_is_preempted function by moving the
> > CIF_ENABLED_WAIT test into arch_vcpu_is_preempted.
> > 
> > Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
> > ---
> 
> hi, Christian
> 	thanks for your patch!
> 
> >  arch/s390/include/asm/spinlock.h |  3 +++
> >  arch/s390/kernel/smp.c           |  9 +++++++--
> >  arch/s390/lib/spinlock.c         | 25 ++++++++-----------------
> >  3 files changed, 18 insertions(+), 19 deletions(-)
> > 
> > diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
> > index 63ebf37..e16e02f 100644
> > --- a/arch/s390/include/asm/spinlock.h
> > +++ b/arch/s390/include/asm/spinlock.h
> > @@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
> >  	return __sync_bool_compare_and_swap(lock, old, new);
> >  }
> > 
> > +bool arch_vcpu_is_preempted(int cpu);
> > +#define vcpu_is_preempted arch_vcpu_is_preempted
> > +
> >  /*
> >   * Simple spin lock operations.  There are two variants, one clears IRQ's
> >   * on the local processor, one does not.
> > diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
> > index 7b89a75..4aadd16 100644
> > --- a/arch/s390/kernel/smp.c
> > +++ b/arch/s390/kernel/smp.c
> > @@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address)
> >  	return -1;
> >  }
> > 
> > -int smp_vcpu_scheduled(int cpu)
> root@ltcalpine2-lp13:~/linux# git grep -wn smp_vcpu_scheduled arch/s390/
> arch/s390/include/asm/smp.h:34:extern int smp_vcpu_scheduled(int cpu);
> arch/s390/include/asm/smp.h:56:static inline int smp_vcpu_scheduled(int cpu) { return 1; }
> arch/s390/kernel/smp.c:371:int smp_vcpu_scheduled(int cpu)
> arch/s390/lib/spinlock.c:44:    if (smp_vcpu_scheduled(cpu))
> 
> > +bool arch_vcpu_is_preempted(int cpu)
> >  {
> > -	return pcpu_running(pcpu_devices + cpu);
> > +	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
> > +		return false;
> > +	if (pcpu_running(pcpu_devices + cpu))
> > +		return false;
> I saw smp_vcpu_scheduled() returns true always on !SMP system.
> 
> maybe we can do somegthing silimar. like below
> 
> #ifndef CONFIG_SMP
> static inline bool arch_vcpu_is_preempted(int cpu) { return !test_cpu_flag_of(CIF_ENABLED_WAIT, cpu); }
> #else
> ...
> 
> but I can't help thinking that if this is a!SMP system, maybe we could only
> #ifndef CONFIG_SMP
> static inline bool arch_vcpu_is_preempted(int cpu) { return false; }
> #else

Why do we need a vcpu_is_preempted() implementation for UP? Where will
you use it?

Regards,
Boqun

> ...
> 
> 
> thanks
> xinhui
> 
> > +	return true;
> >  }
> > +EXPORT_SYMBOL(arch_vcpu_is_preempted);
> > 
> >  void smp_yield_cpu(int cpu)
> >  {
> > diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
> > index e5f50a7..e48a48e 100644
> > --- a/arch/s390/lib/spinlock.c
> > +++ b/arch/s390/lib/spinlock.c
> > @@ -37,15 +37,6 @@ 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)
> > -{
> > -	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
> > -		return 0;
> > -	if (smp_vcpu_scheduled(cpu))
> > -		return 0;
> > -	return 1;
> > -}
> > -
> >  void arch_spin_lock_wait(arch_spinlock_t *lp)
> >  {
> >  	unsigned int cpu = SPINLOCK_LOCKVAL;
> > @@ -62,7 +53,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
> >  			continue;
> >  		}
> >  		/* First iteration: check if the lock owner is running. */
> > -		if (first_diag && cpu_is_preempted(~owner)) {
> > +		if (first_diag && arch_vcpu_is_preempted(~owner)) {
> >  			smp_yield_cpu(~owner);
> >  			first_diag = 0;
> >  			continue;
> > @@ -81,7 +72,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
> >  		 * yield the CPU unconditionally. For LPAR rely on the
> >  		 * sense running status.
> >  		 */
> > -		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
> > +		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
> >  			smp_yield_cpu(~owner);
> >  			first_diag = 0;
> >  		}
> > @@ -108,7 +99,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
> >  			continue;
> >  		}
> >  		/* Check if the lock owner is running. */
> > -		if (first_diag && cpu_is_preempted(~owner)) {
> > +		if (first_diag && arch_vcpu_is_preempted(~owner)) {
> >  			smp_yield_cpu(~owner);
> >  			first_diag = 0;
> >  			continue;
> > @@ -127,7 +118,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
> >  		 * yield the CPU unconditionally. For LPAR rely on the
> >  		 * sense running status.
> >  		 */
> > -		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
> > +		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
> >  			smp_yield_cpu(~owner);
> >  			first_diag = 0;
> >  		}
> > @@ -165,7 +156,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
> >  	owner = 0;
> >  	while (1) {
> >  		if (count-- <= 0) {
> > -			if (owner && cpu_is_preempted(~owner))
> > +			if (owner && arch_vcpu_is_preempted(~owner))
> >  				smp_yield_cpu(~owner);
> >  			count = spin_retry;
> >  		}
> > @@ -211,7 +202,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
> >  	owner = 0;
> >  	while (1) {
> >  		if (count-- <= 0) {
> > -			if (owner && cpu_is_preempted(~owner))
> > +			if (owner && arch_vcpu_is_preempted(~owner))
> >  				smp_yield_cpu(~owner);
> >  			count = spin_retry;
> >  		}
> > @@ -241,7 +232,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
> >  	owner = 0;
> >  	while (1) {
> >  		if (count-- <= 0) {
> > -			if (owner && cpu_is_preempted(~owner))
> > +			if (owner && arch_vcpu_is_preempted(~owner))
> >  				smp_yield_cpu(~owner);
> >  			count = spin_retry;
> >  		}
> > @@ -285,7 +276,7 @@ void arch_lock_relax(unsigned int cpu)
> >  {
> >  	if (!cpu)
> >  		return;
> > -	if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu))
> > +	if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(~cpu))
> >  		return;
> >  	smp_yield_cpu(~cpu);
> >  }
> > 
>

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#1493909

FromPan Xinhui <xinhui@linux.vnet.ibm.com>
Date2016-09-30 08:40 +0200
Message-ID<smZEd-6EC-5@gated-at.bofh.it>
In reply to#1493893

在 2016/9/30 13:52, Boqun Feng 写道:
> On Fri, Sep 30, 2016 at 12:49:52PM +0800, Pan Xinhui wrote:
>>
>>
>> 在 2016/9/29 23:51, Christian Borntraeger 写道:
>>> this implements the s390 backend for commit
>>> "kernel/sched: introduce vcpu preempted check interface"
>>> by reworking the existing smp_vcpu_scheduled into
>>> arch_vcpu_is_preempted. We can then also get rid of the
>>> local cpu_is_preempted function by moving the
>>> CIF_ENABLED_WAIT test into arch_vcpu_is_preempted.
>>>
>>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>> ---
>>
>> hi, Christian
>> 	thanks for your patch!
>>
>>>  arch/s390/include/asm/spinlock.h |  3 +++
>>>  arch/s390/kernel/smp.c           |  9 +++++++--
>>>  arch/s390/lib/spinlock.c         | 25 ++++++++-----------------
>>>  3 files changed, 18 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
>>> index 63ebf37..e16e02f 100644
>>> --- a/arch/s390/include/asm/spinlock.h
>>> +++ b/arch/s390/include/asm/spinlock.h
>>> @@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
>>>  	return __sync_bool_compare_and_swap(lock, old, new);
>>>  }
>>>
>>> +bool arch_vcpu_is_preempted(int cpu);
>>> +#define vcpu_is_preempted arch_vcpu_is_preempted
>>> +
>>>  /*
>>>   * Simple spin lock operations.  There are two variants, one clears IRQ's
>>>   * on the local processor, one does not.
>>> diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
>>> index 7b89a75..4aadd16 100644
>>> --- a/arch/s390/kernel/smp.c
>>> +++ b/arch/s390/kernel/smp.c
>>> @@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address)
>>>  	return -1;
>>>  }
>>>
>>> -int smp_vcpu_scheduled(int cpu)
>> root@ltcalpine2-lp13:~/linux# git grep -wn smp_vcpu_scheduled arch/s390/
>> arch/s390/include/asm/smp.h:34:extern int smp_vcpu_scheduled(int cpu);
>> arch/s390/include/asm/smp.h:56:static inline int smp_vcpu_scheduled(int cpu) { return 1; }
>> arch/s390/kernel/smp.c:371:int smp_vcpu_scheduled(int cpu)
>> arch/s390/lib/spinlock.c:44:    if (smp_vcpu_scheduled(cpu))
>>
>>> +bool arch_vcpu_is_preempted(int cpu)
>>>  {
>>> -	return pcpu_running(pcpu_devices + cpu);
>>> +	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
>>> +		return false;
>>> +	if (pcpu_running(pcpu_devices + cpu))
>>> +		return false;
>> I saw smp_vcpu_scheduled() returns true always on !SMP system.
>>
>> maybe we can do somegthing silimar. like below
>>
>> #ifndef CONFIG_SMP
>> static inline bool arch_vcpu_is_preempted(int cpu) { return !test_cpu_flag_of(CIF_ENABLED_WAIT, cpu); }
>> #else
>> ...
>>
>> but I can't help thinking that if this is a!SMP system, maybe we could only
>> #ifndef CONFIG_SMP
>> static inline bool arch_vcpu_is_preempted(int cpu) { return false; }
>> #else
>
> Why do we need a vcpu_is_preempted() implementation for UP? Where will
> you use it?
>
yep, I also wonder that :)

But there is a definitaion of smp_vcpu_scheduled() for !SMP kernel.
So I am a little worried that some code has included this spinlock.h for UP kernel also.

Hi, Christian
	Could you help confirms that your patch works on UP? :)

thanks
xinhui

> Regards,
> Boqun
>
>> ...
>>
>>
>> thanks
>> xinhui
>>
>>> +	return true;
>>>  }
>>> +EXPORT_SYMBOL(arch_vcpu_is_preempted);
>>>
>>>  void smp_yield_cpu(int cpu)
>>>  {
>>> diff --git a/arch/s390/lib/spinlock.c b/arch/s390/lib/spinlock.c
>>> index e5f50a7..e48a48e 100644
>>> --- a/arch/s390/lib/spinlock.c
>>> +++ b/arch/s390/lib/spinlock.c
>>> @@ -37,15 +37,6 @@ 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)
>>> -{
>>> -	if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
>>> -		return 0;
>>> -	if (smp_vcpu_scheduled(cpu))
>>> -		return 0;
>>> -	return 1;
>>> -}
>>> -
>>>  void arch_spin_lock_wait(arch_spinlock_t *lp)
>>>  {
>>>  	unsigned int cpu = SPINLOCK_LOCKVAL;
>>> @@ -62,7 +53,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
>>>  			continue;
>>>  		}
>>>  		/* First iteration: check if the lock owner is running. */
>>> -		if (first_diag && cpu_is_preempted(~owner)) {
>>> +		if (first_diag && arch_vcpu_is_preempted(~owner)) {
>>>  			smp_yield_cpu(~owner);
>>>  			first_diag = 0;
>>>  			continue;
>>> @@ -81,7 +72,7 @@ void arch_spin_lock_wait(arch_spinlock_t *lp)
>>>  		 * yield the CPU unconditionally. For LPAR rely on the
>>>  		 * sense running status.
>>>  		 */
>>> -		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
>>> +		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
>>>  			smp_yield_cpu(~owner);
>>>  			first_diag = 0;
>>>  		}
>>> @@ -108,7 +99,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
>>>  			continue;
>>>  		}
>>>  		/* Check if the lock owner is running. */
>>> -		if (first_diag && cpu_is_preempted(~owner)) {
>>> +		if (first_diag && arch_vcpu_is_preempted(~owner)) {
>>>  			smp_yield_cpu(~owner);
>>>  			first_diag = 0;
>>>  			continue;
>>> @@ -127,7 +118,7 @@ void arch_spin_lock_wait_flags(arch_spinlock_t *lp, unsigned long flags)
>>>  		 * yield the CPU unconditionally. For LPAR rely on the
>>>  		 * sense running status.
>>>  		 */
>>> -		if (!MACHINE_IS_LPAR || cpu_is_preempted(~owner)) {
>>> +		if (!MACHINE_IS_LPAR || arch_vcpu_is_preempted(~owner)) {
>>>  			smp_yield_cpu(~owner);
>>>  			first_diag = 0;
>>>  		}
>>> @@ -165,7 +156,7 @@ void _raw_read_lock_wait(arch_rwlock_t *rw)
>>>  	owner = 0;
>>>  	while (1) {
>>>  		if (count-- <= 0) {
>>> -			if (owner && cpu_is_preempted(~owner))
>>> +			if (owner && arch_vcpu_is_preempted(~owner))
>>>  				smp_yield_cpu(~owner);
>>>  			count = spin_retry;
>>>  		}
>>> @@ -211,7 +202,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw, unsigned int prev)
>>>  	owner = 0;
>>>  	while (1) {
>>>  		if (count-- <= 0) {
>>> -			if (owner && cpu_is_preempted(~owner))
>>> +			if (owner && arch_vcpu_is_preempted(~owner))
>>>  				smp_yield_cpu(~owner);
>>>  			count = spin_retry;
>>>  		}
>>> @@ -241,7 +232,7 @@ void _raw_write_lock_wait(arch_rwlock_t *rw)
>>>  	owner = 0;
>>>  	while (1) {
>>>  		if (count-- <= 0) {
>>> -			if (owner && cpu_is_preempted(~owner))
>>> +			if (owner && arch_vcpu_is_preempted(~owner))
>>>  				smp_yield_cpu(~owner);
>>>  			count = spin_retry;
>>>  		}
>>> @@ -285,7 +276,7 @@ void arch_lock_relax(unsigned int cpu)
>>>  {
>>>  	if (!cpu)
>>>  		return;
>>> -	if (MACHINE_IS_LPAR && !cpu_is_preempted(~cpu))
>>> +	if (MACHINE_IS_LPAR && !arch_vcpu_is_preempted(~cpu))
>>>  		return;
>>>  	smp_yield_cpu(~cpu);
>>>  }
>>>
>>

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#1495344

FromChristian Borntraeger <borntraeger@de.ibm.com>
Date2016-10-04 12:20 +0200
Message-ID<souZj-1my-13@gated-at.bofh.it>
In reply to#1493909
On 09/30/2016 08:35 AM, Pan Xinhui wrote:
> 
> 
> 在 2016/9/30 13:52, Boqun Feng 写道:
>> On Fri, Sep 30, 2016 at 12:49:52PM +0800, Pan Xinhui wrote:
>>>
>>>
>>> 在 2016/9/29 23:51, Christian Borntraeger 写道:
>>>> this implements the s390 backend for commit
>>>> "kernel/sched: introduce vcpu preempted check interface"
>>>> by reworking the existing smp_vcpu_scheduled into
>>>> arch_vcpu_is_preempted. We can then also get rid of the
>>>> local cpu_is_preempted function by moving the
>>>> CIF_ENABLED_WAIT test into arch_vcpu_is_preempted.
>>>>
>>>> Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
>>>> ---
>>>
>>> hi, Christian
>>>     thanks for your patch!
>>>
>>>>  arch/s390/include/asm/spinlock.h |  3 +++
>>>>  arch/s390/kernel/smp.c           |  9 +++++++--
>>>>  arch/s390/lib/spinlock.c         | 25 ++++++++-----------------
>>>>  3 files changed, 18 insertions(+), 19 deletions(-)
>>>>
>>>> diff --git a/arch/s390/include/asm/spinlock.h b/arch/s390/include/asm/spinlock.h
>>>> index 63ebf37..e16e02f 100644
>>>> --- a/arch/s390/include/asm/spinlock.h
>>>> +++ b/arch/s390/include/asm/spinlock.h
>>>> @@ -21,6 +21,9 @@ _raw_compare_and_swap(unsigned int *lock, unsigned int old, unsigned int new)
>>>>      return __sync_bool_compare_and_swap(lock, old, new);
>>>>  }
>>>>
>>>> +bool arch_vcpu_is_preempted(int cpu);
>>>> +#define vcpu_is_preempted arch_vcpu_is_preempted
>>>> +
>>>>  /*
>>>>   * Simple spin lock operations.  There are two variants, one clears IRQ's
>>>>   * on the local processor, one does not.
>>>> diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
>>>> index 7b89a75..4aadd16 100644
>>>> --- a/arch/s390/kernel/smp.c
>>>> +++ b/arch/s390/kernel/smp.c
>>>> @@ -376,10 +376,15 @@ int smp_find_processor_id(u16 address)
>>>>      return -1;
>>>>  }
>>>>
>>>> -int smp_vcpu_scheduled(int cpu)
>>> root@ltcalpine2-lp13:~/linux# git grep -wn smp_vcpu_scheduled arch/s390/
>>> arch/s390/include/asm/smp.h:34:extern int smp_vcpu_scheduled(int cpu);
>>> arch/s390/include/asm/smp.h:56:static inline int smp_vcpu_scheduled(int cpu) { return 1; }
>>> arch/s390/kernel/smp.c:371:int smp_vcpu_scheduled(int cpu)
>>> arch/s390/lib/spinlock.c:44:    if (smp_vcpu_scheduled(cpu))
>>>
>>>> +bool arch_vcpu_is_preempted(int cpu)
>>>>  {
>>>> -    return pcpu_running(pcpu_devices + cpu);
>>>> +    if (test_cpu_flag_of(CIF_ENABLED_WAIT, cpu))
>>>> +        return false;
>>>> +    if (pcpu_running(pcpu_devices + cpu))
>>>> +        return false;
>>> I saw smp_vcpu_scheduled() returns true always on !SMP system.
>>>
>>> maybe we can do somegthing silimar. like below
>>>
>>> #ifndef CONFIG_SMP
>>> static inline bool arch_vcpu_is_preempted(int cpu) { return !test_cpu_flag_of(CIF_ENABLED_WAIT, cpu); }
>>> #else
>>> ...
>>>
>>> but I can't help thinking that if this is a!SMP system, maybe we could only
>>> #ifndef CONFIG_SMP
>>> static inline bool arch_vcpu_is_preempted(int cpu) { return false; }
>>> #else
>>
>> Why do we need a vcpu_is_preempted() implementation for UP? Where will
>> you use it?
>>
> yep, I also wonder that :)
> 
> But there is a definitaion of smp_vcpu_scheduled() for !SMP kernel.
> So I am a little worried that some code has included this spinlock.h for UP kernel also.
> 
> Hi, Christian
>     Could you help confirms that your patch works on UP? :)

My patch as is seems to work fine for !SMP. So it looks like the extra define
is not necessary and we could simply go with v2

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#1494142

FromChristian Borntraeger <borntraeger@de.ibm.com>
Date2016-09-30 16:40 +0200
Message-ID<sn78J-2XU-7@gated-at.bofh.it>
In reply to#1493881
On 09/30/2016 06:49 AM, Pan Xinhui wrote:

> 
> but I can't help thinking that if this is a!SMP system, maybe we could only
> #ifndef CONFIG_SMP
> static inline bool arch_vcpu_is_preempted(int cpu) { return false; }
> #else

Yes, I will add that to v3. Thanks for spotting.

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