linux-kernel - [RFC] sched: add sched_show_task() variant that accepts log level

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Message-ID: <miliiyxmqko6hx66yhdv4nkkopbm73wbz6kxxlzpts53mscqzy@dpfa6y3wnspv>
Date: Mon, 10 Mar 2025 17:25:37 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>, 
	Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, 
	Valentin Schneider <vschneid@...hat.com>, Tomasz Figa <tfiga@...omium.org>, linux-kernel@...r.kernel.org
Subject: [RFC] sched: add sched_show_task() variant that accepts log level

Hi,

A request for comments, not a formal patch.

Is there any reason why hung-task watchdog prints error header
with KERN_ERR log level while task's backtrace is printed with
KERN_INFO?  Will it make sense to unify log levels and introduce
sched_show_task() variant that accept log level param so that
everything that hung-task watchdog prints becomes KERN_ERR?

Something like this:

---
 include/linux/sched/debug.h |  1 +
 kernel/hung_task.c          |  4 ++--
 kernel/sched/core.c         | 19 +++++++++++++------
 3 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/include/linux/sched/debug.h b/include/linux/sched/debug.h
index b5035afa2396..8e46854d16fc 100644
--- a/include/linux/sched/debug.h
+++ b/include/linux/sched/debug.h
@@ -34,6 +34,7 @@ extern void show_stack(struct task_struct *task, unsigned long *sp,
 		       const char *loglvl);
 
 extern void sched_show_task(struct task_struct *p);
+extern void sched_show_task_log_lvl(struct task_struct *p, const char *lvl);
 
 #ifdef CONFIG_SCHED_DEBUG
 struct seq_file;
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index ccd7217fcec1..23dec32a05f3 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -119,7 +119,7 @@ static void debug_show_blocker(struct task_struct *task)
 		if ((unsigned long)t == owner) {
 			pr_err("INFO: task %s:%d is blocked on a mutex likely owned by task %s:%d.\n",
 				task->comm, task->pid, t->comm, t->pid);
-			sched_show_task(t);
+			sched_show_task_log_lvl(t, KERN_ERR);
 			return;
 		}
 	}
@@ -186,7 +186,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 			pr_err("      Blocked by coredump.\n");
 		pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\""
 			" disables this message.\n");
-		sched_show_task(t);
+		sched_show_task_log_lvl(t, KERN_ERR);
 		debug_show_blocker(t);
 		hung_task_show_lock = true;
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 00ea6f31973c..b6a5a41fbbfc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7687,7 +7687,7 @@ void __sched io_schedule(void)
 }
 EXPORT_SYMBOL(io_schedule);
 
-void sched_show_task(struct task_struct *p)
+void sched_show_task_log_lvl(struct task_struct *p, const char *lvl)
 {
 	unsigned long free;
 	int ppid;
@@ -7695,7 +7695,8 @@ void sched_show_task(struct task_struct *p)
 	if (!try_get_task_stack(p))
 		return;
 
-	pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p));
+	printk("%stask:%-15.15s state:%c", lvl,
+	       p->comm, task_state_to_char(p));
 
 	if (task_is_running(p))
 		pr_cont("  running task    ");
@@ -7709,12 +7710,18 @@ void sched_show_task(struct task_struct *p)
 		free, task_pid_nr(p), task_tgid_nr(p),
 		ppid, p->flags, read_task_thread_flags(p));
 
-	print_worker_info(KERN_INFO, p);
-	print_stop_info(KERN_INFO, p);
-	print_scx_info(KERN_INFO, p);
-	show_stack(p, NULL, KERN_INFO);
+	print_worker_info(lvl, p);
+	print_stop_info(lvl, p);
+	print_scx_info(lvl, p);
+	show_stack(p, NULL, lvl);
 	put_task_stack(p);
 }
+EXPORT_SYMBOL_GPL(sched_show_task_log_lvl);
+
+void sched_show_task(struct task_struct *p)
+{
+	sched_show_task_log_lvl(p, KERN_INFO);
+}
 EXPORT_SYMBOL_GPL(sched_show_task);
 
 static inline bool
-- 
2.49.0.rc0.332.g42c0ae87b1-goog