On 09/29/2016 12:23 PM, Christian Borntraeger wrote:
> On 09/29/2016 12:10 PM, Peter Zijlstra wrote:
>> On Thu, Jul 21, 2016 at 07:45:10AM -0400, Pan Xinhui wrote:
>>> change from v2:
>>> no code change, fix typos, update some comments
>>>
>>> change from v1:
>>> a simplier definition of default vcpu_is_preempted
>>> skip mahcine type check on ppc, and add config. remove dedicated macro.
>>> add one patch to drop overload of rwsem_spin_on_owner and mutex_spin_on_owner.
>>> add more comments
>>> thanks boqun and Peter's suggestion.
>>>
>>> This patch set aims to fix lock holder preemption issues.
>>
>> So I really like the concept, but I would also really like to see
>> support for more hypervisors included before we can move forward with
>> this.
>>
>> Please consider s390 and (x86/arm) KVM. Once we have a few, more can
>> follow later, but I think its important to not only have PPC support for
>> this.
>
> Actually the s390 preemted check via sigp sense running is available for
> all hypervisors (z/VM, LPAR and KVM) which implies everywhere as you can no
> longer buy s390 systems without LPAR.
>
> As Heiko already pointed out we could simply use a small inline function
> that calls cpu_is_preempted from arch/s390/lib/spinlock (or smp_vcpu_scheduled from smp.c)
Maybe something like
(untested and just pasted, so white space damaged)
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..260d179 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)
{
If ok I can respin into a proper patch.
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