[RFC v2 8/9] sysfs: Add cpu_avoid file

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Add a sysfs file called "avoid" which prints the current CPUs 
makred as avoid. 

This could be used by userspace components or tools such as irqbalance. 

/sys/devices/system/cpu # cat avoid 
70-479

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
 drivers/base/cpu.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
index 7779ab0ca7ce..51c1207f6f33 100644
--- a/drivers/base/cpu.c
+++ b/drivers/base/cpu.c
@@ -300,6 +300,13 @@ static ssize_t print_cpus_isolated(struct device *dev,
 }
 static DEVICE_ATTR(isolated, 0444, print_cpus_isolated, NULL);
 
+static ssize_t print_cpus_avoid(struct device *dev,
+				struct device_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%*pbl\n", cpumask_pr_args(cpu_avoid_mask));
+}
+static DEVICE_ATTR(avoid, 0444, print_cpus_avoid, NULL);
+
 #ifdef CONFIG_NO_HZ_FULL
 static ssize_t print_cpus_nohz_full(struct device *dev,
 				    struct device_attribute *attr, char *buf)
@@ -505,6 +512,7 @@ static struct attribute *cpu_root_attrs[] = {
 	&dev_attr_offline.attr,
 	&dev_attr_enabled.attr,
 	&dev_attr_isolated.attr,
+	&dev_attr_avoid.attr,
 #ifdef CONFIG_NO_HZ_FULL
 	&dev_attr_nohz_full.attr,
 #endif
-- 
2.43.0