Thread (2 messages) 2 messages, 2 authors, 2016-09-29

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

From: Martin Schwidefsky <hidden>
Date: 2016-09-29 13:11:16

On Thu, 29 Sep 2016 13:54:16 +0200
Christian Borntraeger [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted>
---
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.
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