linux-kernel - [PATCH] hung_task: configurable hung-task stacktrace loglevel

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Message-ID: <20250424070436.2380215-1-senozhatsky@chromium.org>
Date: Thu, 24 Apr 2025 16:02:43 +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>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Tomasz Figa <tfiga@...omium.org>,
	Petr Mladek <pmladek@...e.com>,
	John Ogness <john.ogness@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: [PATCH] hung_task: configurable hung-task stacktrace loglevel

Currently, hung-task watchdog uses two different loglevels
to report hung-tasks: a) KERN_INFO for all the important task
information (e.g. sched_show_task()) and b)  KERN_ERR for the
rest.  This makes it a little inconvenient, especially for
automated kernel logs parsing.

Introduce CONFIG_HUNG_TASK_STACKTRACE_LOGLEVEL so that (a)
becomes configurable.

Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 include/linux/sched/debug.h |  1 +
 kernel/hung_task.c          |  6 ++++--
 kernel/sched/core.c         | 19 +++++++++++++------
 lib/Kconfig.debug           |  8 ++++++++
 4 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/include/linux/sched/debug.h b/include/linux/sched/debug.h
index 35ed4577a6cc..80c17cdd35a8 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);
 
 struct seq_file;
 extern void proc_sched_show_task(struct task_struct *p,
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index d2432df2b905..8817016fd45b 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -26,6 +26,8 @@
 
 #include <trace/events/sched.h>
 
+#define PR_LEVEL KERN_SOH __stringify(CONFIG_HUNG_TASK_STACKTRACE_LOGLEVEL)
+
 /*
  * The number of tasks checked:
  */
@@ -153,7 +155,7 @@ static void debug_show_blocker(struct task_struct *task)
 			       task->comm, task->pid, t->comm, t->pid);
 			break;
 		}
-		sched_show_task(t);
+		sched_show_task_log_lvl(t, PR_LEVEL);
 		return;
 	}
 }
@@ -221,7 +223,7 @@ 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, PR_LEVEL);
 		debug_show_blocker(t);
 		hung_task_show_lock = true;
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 54e7d63f7785..e9033b049092 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7751,7 +7751,7 @@ 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;
@@ -7759,7 +7759,8 @@ 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    ");
@@ -7773,12 +7774,18 @@ 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
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 3e40f68a4a4f..6cd266651447 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1290,6 +1290,14 @@ config DETECT_HUNG_TASK_BLOCKER
 	  This will add overhead a bit but shows suspicious tasks and
 	  call trace if it comes from waiting a mutex.
 
+config HUNG_TASK_STACKTRACE_LOGLEVEL
+	int "Log-level for hung task stacktrace (1-7)"
+	depends on DETECT_HUNG_TASK
+	default "6"
+	help
+	  This option controls the log-level used to print the stacktrace
+	  of the hung task. The default is 6 (KERN_INFO).
+
 config WQ_WATCHDOG
 	bool "Detect Workqueue Stalls"
 	depends on DEBUG_KERNEL
-- 
2.49.0.805.g082f7c87e0-goog