linux-kernel - [RFC v2 8/9] sysfs: Add cpu

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Message-ID: <20250625191108.1646208-9-sshegde@linux.ibm.com>
Date: Thu, 26 Jun 2025 00:41:07 +0530
From: Shrikanth Hegde <sshegde@...ux.ibm.com>
To: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, tglx@...utronix.de, yury.norov@...il.com,
        maddy@...ux.ibm.com
Cc: sshegde@...ux.ibm.com, vschneid@...hat.com, dietmar.eggemann@....com,
        rostedt@...dmis.org, kprateek.nayak@....com, huschle@...ux.ibm.com,
        srikar@...ux.ibm.com, linux-kernel@...r.kernel.org,
        christophe.leroy@...roup.eu, linuxppc-dev@...ts.ozlabs.org,
        gregkh@...uxfoundation.org
Subject: [RFC v2 8/9] sysfs: Add cpu_avoid file

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@...ux.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