linux-kernel - [PATCH] sched: print parent comm in sched_show

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Message-ID: <20221227161400.GA7646@didi-ThinkCentre-M930t-N000>
Date:   Wed, 28 Dec 2022 00:14:00 +0800
From:   Tio Zhang <tiozhang@...iglobal.com>
To:     <mingo@...hat.com>, <peterz@...radead.org>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>
CC:     <linux-kernel@...r.kernel.org>, <pmladek@...e.com>,
        <zyhtheonly@...il.com>, <zyhtheonly@...h.net>, <zwp10758@...il.com>
Subject: [PATCH] sched: print parent comm in sched_show_task()

Knowing who the parent is might be useful for debugging.
For example, we can sometimes resolve kernel hung tasks by stopping
the person who begins those hung tasks.
With the parent's name printed in sched_show_task(),
it might be helpful to let people know which "service" should be operated.

Signed-off-by: Tio Zhang <tiozhang@...iglobal.com>
---
 kernel/sched/core.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index cb2aa2b54c7a..6f4aef0fed58 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8854,6 +8854,7 @@ void sched_show_task(struct task_struct *p)
 {
 	unsigned long free = 0;
 	int ppid;
+	char pcomm[TASK_COMM_LEN];
 
 	if (!try_get_task_stack(p))
 		return;
@@ -8867,11 +8868,13 @@ void sched_show_task(struct task_struct *p)
 #endif
 	ppid = 0;
 	rcu_read_lock();
-	if (pid_alive(p))
+	if (pid_alive(p)) {
 		ppid = task_pid_nr(rcu_dereference(p->real_parent));
+		get_task_comm(pcomm, rcu_dereference(p->real_parent));
+	}
 	rcu_read_unlock();
-	pr_cont(" stack:%-5lu pid:%-5d ppid:%-6d flags:0x%08lx\n",
-		free, task_pid_nr(p), ppid,
+	pr_cont(" stack:%-5lu pid:%-5d ppid:%-6d parent:%-15.15s flags:0x%08lx\n",
+		free, task_pid_nr(p), ppid, pcomm,
 		read_task_thread_flags(p));
 
 	print_worker_info(KERN_INFO, p);
-- 
2.17.1