[PATCH v2 2/3] kernel: set taint flag 'L' at any kind of lockup

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

Any lockup or stall detector notifies about unexpected lack of progress.
It's better to know about these splats at investigating further problems.

This patch set TAINT_LOCKUP at:
- softlockup (CONFIG_SOFTLOCKUP_DETECTOR)
- hardlockup (CONFIG_HARDLOCKUP_DETECTOR)
- RCU stall (Documentation/RCU/stallwarn.txt)
- hung task (CONFIG_DETECT_HUNG_TASK)
- stuck in workqueues (CONFIG_WQ_WATCHDOG)

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Acked-by: Paul E. McKenney <paulmck@kernel.org> (RCU part)
Link: https://lore.kernel.org/lkml/157503370645.8187.6335564487789994134.stgit@buzz/ (v1)
---
 Documentation/admin-guide/tainted-kernels.rst |    4 ++++
 kernel/hung_task.c                            |    2 ++
 kernel/rcu/tree_stall.h                       |    1 +
 kernel/watchdog_hld.c                         |    1 +
 kernel/workqueue.c                            |    1 +
 5 files changed, 9 insertions(+)

diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
index 55d45211cb41..13249240283c 100644
--- a/Documentation/admin-guide/tainted-kernels.rst
+++ b/Documentation/admin-guide/tainted-kernels.rst
@@ -153,6 +153,10 @@ More detailed explanation for tainting
      module signature.
 
  14) ``L`` if a lockup has previously occurred on the system.
+     - soft/hardlockup, see Documentation/admin-guide/lockup-watchdogs.rst
+     - RCU stall, see Documentation/RCU/stallwarn.txt
+     - hung task detected, see CONFIG_DETECT_HUNG_TASK
+     - kernel workqueue lockup, see CONFIG_WQ_WATCHDOG
 
  15) ``K`` if the kernel has been live patched.
 
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 14a625c16cb3..521eb2fbf5fc 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -139,6 +139,8 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout)
 		hung_task_show_lock = true;
 	}
 
+	add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK);
+
 	touch_nmi_watchdog();
 }
 
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index c0b8c458d8a6..181495efff80 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -74,6 +74,7 @@ early_initcall(check_cpu_stall_init);
 /* If so specified via sysctl, panic, yielding cleaner stall-warning output. */
 static void panic_on_rcu_stall(void)
 {
+	add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK);
 	if (sysctl_panic_on_rcu_stall)
 		panic("RCU Stall\n");
 }
diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 247bf0b1582c..f77256f47422 100644
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -152,6 +152,7 @@ static void watchdog_overflow_callback(struct perf_event *event,
 				!test_and_set_bit(0, &hardlockup_allcpu_dumped))
 			trigger_allbutself_cpu_backtrace();
 
+		add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK);
 		if (hardlockup_panic)
 			nmi_panic(regs, "Hard LOCKUP");
 
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index cfc923558e04..1b3c81d87a0d 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -5774,6 +5774,7 @@ static void wq_watchdog_timer_fn(struct timer_list *unused)
 			pr_cont_pool_info(pool);
 			pr_cont(" stuck for %us!\n",
 				jiffies_to_msecs(jiffies - pool_ts) / 1000);
+			add_taint(TAINT_LOCKUP, LOCKDEP_STILL_OK);
 		}
 	}