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Message-Id: <20251113111039.22701-3-feng.tang@linux.alibaba.com>
Date: Thu, 13 Nov 2025 19:10:37 +0800
From: Feng Tang <feng.tang@...ux.alibaba.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
Petr Mladek <pmladek@...e.com>,
Lance Yang <ioworker0@...il.com>,
Jonathan Corbet <corbet@....net>,
paulmck@...nel.org,
Steven Rostedt <rostedt@...dmis.org>,
linux-kernel@...r.kernel.org
Cc: Feng Tang <feng.tang@...ux.alibaba.com>
Subject: [PATCH v2 2/4] hung_task: Add hung_task_sys_info sysctl to dump sys info on task-hung
When task-hung happens, developers may need different kinds of system
information (call-stacks, memory info, locks, etc.) to help debugging.
Add 'hung_task_sys_info' sysctl knob to take human readable string like
"tasks,mem,timers,locks,ftrace,...", and when task-hung happens, all
requested information will be dumped. (refer kernel/sys_info.c for more
details).
Meanwhile, the newly introduced sys_info() call is used to unify some
existing info-dumping knobs.
Suggested-by: Petr Mladek <pmladek@...e.com>
Signed-off-by: Feng Tang <feng.tang@...ux.alibaba.com>
---
Documentation/admin-guide/sysctl/kernel.rst | 5 ++
kernel/hung_task.c | 62 +++++++++++++--------
2 files changed, 43 insertions(+), 24 deletions(-)
diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index a397eeccaea7..45b4408dad31 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -422,6 +422,11 @@ the system boot.
This file shows up if ``CONFIG_DETECT_HUNG_TASK`` is enabled.
+hung_task_sys_info
+==================
+A comma separated list of extra system information to be dumped when
+hung task is detected, for example, "tasks,mem,timers,locks,...".
+Refer 'panic_sys_info' section below for more details.
hung_task_timeout_secs
======================
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 5ac0e66a1361..5b3a7785d3a2 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -24,6 +24,7 @@
#include <linux/sched/sysctl.h>
#include <linux/hung_task.h>
#include <linux/rwsem.h>
+#include <linux/sys_info.h>
#include <trace/events/sched.h>
@@ -59,12 +60,17 @@ static unsigned long __read_mostly sysctl_hung_task_check_interval_secs;
static int __read_mostly sysctl_hung_task_warnings = 10;
static int __read_mostly did_panic;
-static bool hung_task_show_lock;
static bool hung_task_call_panic;
-static bool hung_task_show_all_bt;
static struct task_struct *watchdog_task;
+/*
+ * A bitmask to control what kinds of system info to be printed when
+ * a hung task is detected, it could be task, memory, lock etc. Refer
+ * include/linux/sys_info.h for detailed bit definition.
+ */
+static unsigned long hung_task_si_mask;
+
#ifdef CONFIG_SMP
/*
* Should we dump all CPUs backtraces in a hung task event?
@@ -217,11 +223,8 @@ static inline void debug_show_blocker(struct task_struct *task, unsigned long ti
}
#endif
-static void check_hung_task(struct task_struct *t, unsigned long timeout,
- unsigned long prev_detect_count)
+static void check_hung_task(struct task_struct *t, unsigned long timeout)
{
- unsigned long total_hung_task;
-
if (!task_is_hung(t, timeout))
return;
@@ -231,20 +234,13 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout,
*/
sysctl_hung_task_detect_count++;
- total_hung_task = sysctl_hung_task_detect_count - prev_detect_count;
trace_sched_process_hang(t);
- if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) {
- console_verbose();
- hung_task_show_lock = true;
- hung_task_call_panic = true;
- }
-
/*
* Ok, the task did not get scheduled for more than 2 minutes,
* complain:
*/
- if (sysctl_hung_task_warnings || hung_task_call_panic) {
+ if (sysctl_hung_task_warnings) {
if (sysctl_hung_task_warnings > 0)
sysctl_hung_task_warnings--;
pr_err("INFO: task %s:%d blocked for more than %ld seconds.\n",
@@ -259,10 +255,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout,
" disables this message.\n");
sched_show_task(t);
debug_show_blocker(t, timeout);
- hung_task_show_lock = true;
- if (sysctl_hung_task_all_cpu_backtrace)
- hung_task_show_all_bt = true;
if (!sysctl_hung_task_warnings)
pr_info("Future hung task reports are suppressed, see sysctl kernel.hung_task_warnings\n");
}
@@ -302,8 +295,11 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
{
int max_count = sysctl_hung_task_check_count;
unsigned long last_break = jiffies;
+ unsigned long total_hung_task;
struct task_struct *g, *t;
unsigned long prev_detect_count = sysctl_hung_task_detect_count;
+ int need_warning = sysctl_hung_task_warnings;
+ unsigned long si_mask = hung_task_si_mask;
/*
* If the system crashed already then all bets are off,
@@ -312,7 +308,7 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
if (test_taint(TAINT_DIE) || did_panic)
return;
- hung_task_show_lock = false;
+
rcu_read_lock();
for_each_process_thread(g, t) {
@@ -324,18 +320,29 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
last_break = jiffies;
}
- check_hung_task(t, timeout, prev_detect_count);
+ check_hung_task(t, timeout);
}
unlock:
rcu_read_unlock();
- if (hung_task_show_lock)
- debug_show_all_locks();
- if (hung_task_show_all_bt) {
- hung_task_show_all_bt = false;
- trigger_all_cpu_backtrace();
+ total_hung_task = sysctl_hung_task_detect_count - prev_detect_count;
+ if (!total_hung_task)
+ return;
+
+ if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) {
+ console_verbose();
+ hung_task_call_panic = true;
+ }
+
+ if (need_warning || hung_task_call_panic) {
+ si_mask |= SYS_INFO_LOCKS;
+
+ if (sysctl_hung_task_all_cpu_backtrace)
+ si_mask |= SYS_INFO_ALL_BT;
}
+ sys_info(si_mask);
+
if (hung_task_call_panic)
panic("hung_task: blocked tasks");
}
@@ -434,6 +441,13 @@ static const struct ctl_table hung_task_sysctls[] = {
.mode = 0444,
.proc_handler = proc_doulongvec_minmax,
},
+ {
+ .procname = "hung_task_sys_info",
+ .data = &hung_task_si_mask,
+ .maxlen = sizeof(hung_task_si_mask),
+ .mode = 0644,
+ .proc_handler = sysctl_sys_info_handler,
+ },
};
static void __init hung_task_sysctl_init(void)
--
2.43.5
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