linux-kernel - [PATCH] sched/proc: Print user_cpus

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Date: Mon, 29 Apr 2024 16:46:33 +0800
From: Xuewen Yan <xuewen.yan@...soc.com>
To: <akpm@...ux-foundation.org>, <oleg@...hat.com>, <longman@...hat.com>,
        <peterz@...radead.org>
CC: <dylanbhatch@...gle.com>, <rick.p.edgecombe@...el.com>,
        <ke.wang@...soc.com>, <xuewen.yan94@...il.com>,
        <linux-kernel@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>
Subject: [PATCH] sched/proc: Print user_cpus_ptr for task status

The commit 851a723e45d1c("sched: Always clear user_cpus_ptr in do_set_cpus_allowed()")
would clear the user_cpus_ptr when call the do_set_cpus_allowed.

In order to determine whether the user_cpus_ptr is taking effect,
it is better to print the task's user_cpus_ptr.

For top-cpuset:
ums9621_1h10:/ # while true; do done&
[1] 6786
ums9621_1h10:/ # cat /proc/6786/status | grep Cpus
Cpus_allowed:   ff
Cpus_allowed_list:      0-7
Cpus_user_allowed:        (null)
Cpus_user_allowed_list:   (null)

bind the task to 6-7：
ums9621_1h10:/ # taskset -p c0 6786
pid 6786's current affinity mask: ff
pid 6786's new affinity mask: c0
ums9621_1h10:/ # cat /proc/6786/status | grep Cpus
Cpus_allowed:   c0
Cpus_allowed_list:      6-7
Cpus_user_allowed:      c0
Cpus_user_allowed_list: 6-7

Offline cpu7:
ums9621_1h10:/ # echo 0 > /sys/devices/system/cpu/cpu7/online
ums9621_1h10:/ # cat /proc/6786/status | grep Cpus
Cpus_allowed:   c0
Cpus_allowed_list:      6-7
Cpus_user_allowed:      c0
Cpus_user_allowed_list: 6-7

Offline cpu6, and then the do_set_cpus_allowed will clear the user_ptr:
ums9621_1h10:/ # echo 0 > /sys/devices/system/cpu/cpu6/online
ums9621_1h10:/ # cat /proc/6786/status | grep Cpus
Cpus_allowed:   ff
Cpus_allowed_list:      0-7
Cpus_user_allowed:        (null)
Cpus_user_allowed_list:   (null)

Bringup the core6,7:
ums9621_1h10:/ # echo 1 > /sys/devices/system/cpu/cpu6/online
ums9621_1h10:/ # echo 1 > /sys/devices/system/cpu/cpu7/online
ums9621_1h10:/ # cat /proc/6786/status | grep Cpus
Cpus_allowed:   ff
Cpus_allowed_list:      0-7
Cpus_user_allowed:        (null)
Cpus_user_allowed_list:   (null)

Signed-off-by: Xuewen Yan <xuewen.yan@...soc.com>
---
 fs/proc/array.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 34a47fb0c57f..084bee2a2e2b 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -409,6 +409,10 @@ static void task_cpus_allowed(struct seq_file *m, struct task_struct *task)
 		   cpumask_pr_args(&task->cpus_mask));
 	seq_printf(m, "Cpus_allowed_list:\t%*pbl\n",
 		   cpumask_pr_args(&task->cpus_mask));
+	seq_printf(m, "Cpus_user_allowed:\t%*pb\n",
+		   cpumask_pr_args(task->user_cpus_ptr));
+	seq_printf(m, "Cpus_user_allowed_list:\t%*pbl\n",
+		   cpumask_pr_args(task->user_cpus_ptr));
 }
 
 static inline void task_core_dumping(struct seq_file *m, struct task_struct *task)
-- 
2.25.1