powerpc: Make sysfs code use smp_call_function_single

Impact: performance improvement

This fixes 'powerpc: avoid cpumask games in arch/powerpc/kernel/sysfs.c'
which talked about using smp_call_function_single, but actually used
work_on_cpu (an older version of the patch).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/sysfs.c

@@ -134,36 +134,16 @@ void ppc_enable_pmcs(void)
 }
 EXPORT_SYMBOL(ppc_enable_pmcs);
 
-#if defined(CONFIG_6xx) || defined(CONFIG_PPC64)
-/* XXX convert to rusty's on_one_cpu */
-static unsigned long run_on_cpu(unsigned long cpu,
-			        unsigned long (*func)(unsigned long),
-				unsigned long arg)
-{
-	cpumask_t old_affinity = current->cpus_allowed;
-	unsigned long ret;
-
-	/* should return -EINVAL to userspace */
-	if (set_cpus_allowed(current, cpumask_of_cpu(cpu)))
-		return 0;
-
-	ret = func(arg);
-
-	set_cpus_allowed(current, old_affinity);
-
-	return ret;
-}
-#endif
 
 #define SYSFS_PMCSETUP(NAME, ADDRESS) \
-static unsigned long read_##NAME(unsigned long junk) \
+static void read_##NAME(void *val) \
 { \
-	return mfspr(ADDRESS); \
+	mtspr(ADDRESS, *(unsigned long *)val);	\
 } \
 static unsigned long write_##NAME(unsigned long val) \
 { \
 	ppc_enable_pmcs(); \
-	mtspr(ADDRESS, val); \
+	mtspr(ADDRESS, *(unsigned long *)val);	\
 	return 0; \
 } \
 static ssize_t show_##NAME(struct sys_device *dev, \
@@ -171,7 +151,8 @@ static ssize_t show_##NAME(struct sys_device *dev, \
 			char *buf) \
 { \
 	struct cpu *cpu = container_of(dev, struct cpu, sysdev); \
-	unsigned long val = run_on_cpu(cpu->sysdev.id, read_##NAME, 0); \
+	unsigned long val; \
+	smp_call_function_single(cpu->sysdev.id, read_##NAME, &val, 1);	\
 	return sprintf(buf, "%lx\n", val); \
 } \
 static ssize_t __used \
@@ -183,7 +164,7 @@ static ssize_t __used \
 	int ret = sscanf(buf, "%lx", &val); \
 	if (ret != 1) \
 		return -EINVAL; \
-	run_on_cpu(cpu->sysdev.id, write_##NAME, val); \
+	smp_call_function_single(cpu->sysdev.id, write_##NAME, &val, 1); \
 	return count; \
 }