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.

[feng.tang@linux.alibaba.com: maintain consistecy established behavior, per Lance and Petr]
Link: https://lkml.kernel.org/r/aRncJo1mA5Zk77Hr@U-2FWC9VHC-2323.local
Link: https://lkml.kernel.org/r/20251113111039.22701-3-feng.tang@linux.alibaba.com
Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>
Suggested-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Lance Yang <lance.yang@linux.dev>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: "Paul E . McKenney" <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index a397eeccaea7314581f9d2090b1567060952090b..45b4408dad3165805cad16ef60cf2d00eff24a4a 100644 (file)
--- 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 5ac0e66a13615a6cf54a00fbda5dc6fc7dab8f68..d2254c91450b2edc45365d3005d2b2809c3fb571 100644 (file)
--- 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?
@@ -236,7 +242,6 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout,
 
        if (sysctl_hung_task_panic && total_hung_task >= sysctl_hung_task_panic) {
                console_verbose();
-               hung_task_show_lock = true;
                hung_task_call_panic = true;
        }
 
@@ -259,10 +264,7 @@ 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");
        }
@@ -304,6 +306,8 @@ static void check_hung_uninterruptible_tasks(unsigned long timeout)
        unsigned long last_break = jiffies;
        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 +316,7 @@ 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) {
 
@@ -328,14 +332,19 @@ static void check_hung_uninterruptible_tasks(unsigned long 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();
+       if (!(sysctl_hung_task_detect_count - prev_detect_count))
+               return;
+
+       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 +443,13 @@ 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)