Re: [PATCH 17/20] SMP: Implement on_cpu()

[Avi Kivity]

Avi Kivity wrote:
> Andi Kleen wrote:
> > > Well, smp_call_function_single() is arch specific whereas on_cpu() is
> > >     
> >
> > Yes, but the few instances should be relatively easy to fix.
> >
> >  
> > > generic code.  Perhaps rename smp_call_function_single() to
> > > __smp_call_function_single() and on_cpu() to 
> > > smp_call_function_single()?
> > >     
> >
> > The low level function checks for this anyways. Instead of erroring
> > it should just DTRT.
> >   
>
> Okay.  I'll make that change.

Here it is (whitespace-mangled, don't try to apply).

diff --git a/arch/i386/kernel/smpcommon.c b/arch/i386/kernel/smpcommon.c
index 1868ae1..bbfe85a 100644
--- a/arch/i386/kernel/smpcommon.c
+++ b/arch/i386/kernel/smpcommon.c
@@ -47,7 +47,7 @@ int smp_call_function(void (*func) (void *info), void *info, int nonatomic,
EXPORT_SYMBOL(smp_call_function);

/**
- * smp_call_function_single - Run a function on another CPU
+ * smp_call_function_single - Run a function on a specific CPU
 * @cpu: The target CPU.  Cannot be the calling CPU.
 * @func: The function to run. This must be fast and non-blocking.
 * @info: An arbitrary pointer to pass to the function.
@@ -66,9 +66,11 @@ int smp_call_function_single(int cpu, void (*func) (void *info), void *info,
	int ret;
	int me = get_cpu();
	if (cpu == me) {
-		WARN_ON(1);
+		local_irq_disable();
+		func(info);
+		local_irq_enable();
		put_cpu();
-		return -EBUSY;
+		return 0;
	}

	ret = smp_call_function_mask(cpumask_of_cpu(cpu), func, info, wait);
diff --git a/arch/x86_64/kernel/smp.c b/arch/x86_64/kernel/smp.c
index 2ff4685..e6e5017 100644
--- a/arch/x86_64/kernel/smp.c
+++ b/arch/x86_64/kernel/smp.c
@@ -357,7 +357,7 @@ __smp_call_function_single(int cpu, void (*func) (void *info), void *info,
}

/*
- * smp_call_function_single - Run a function on another CPU
+ * smp_call_function_single - Run a function on a specific CPU
 * @func: The function to run. This must be fast and non-blocking.
 * @info: An arbitrary pointer to pass to the function.
 * @nonatomic: Currently unused.
@@ -372,16 +372,19 @@ __smp_call_function_single(int cpu, void (*func) (void *info), void *info,
int smp_call_function_single (int cpu, void (*func) (void *info), void *info,
	int nonatomic, int wait)
{
+	/* Can deadlock when called with interrupts disabled */
+	WARN_ON(irqs_disabled());
+
	/* prevent preemption and reschedule on another processor */
	int me = get_cpu();
	if (cpu == me) {
+		local_irq_disable();
+		func(info);
+		local_irq_enable();
		put_cpu();
		return 0;
	}

-	/* Can deadlock when called with interrupts disabled */
-	WARN_ON(irqs_disabled());
-
	spin_lock_bh(&call_lock);
	__smp_call_function_single(cpu, func, info, nonatomic, wait);
	spin_unlock_bh(&call_lock);
diff --git a/include/linux/smp.h b/include/linux/smp.h
index 613edd2..ed38a3d 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -118,7 +118,11 @@ static inline void smp_send_reschedule(int cpu) { }
static inline int smp_call_function_single(int cpuid, void (*func) (void *info),
					   void *info, int retry, int wait)
{
-	return -EBUSY;
+	WARN_ON(cpuid != 0);
+	local_irq_disable();
+	func(info);
+	local_irq_enable();
+	return 0;
}

#endif /* !SMP */


If there are no objections, I will push it (split up) through my kvm updates patchset, as other kvm patches depend on it.  I will submit patches to other archs through the arch maintainers as kvm doesn't care about them yet.


--
error compiling committee.c: too many arguments to function

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