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

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Date:   Mon, 27 Jan 2020 17:03:44 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Cc:     Sasha Levin <sashal@...nel.org>, Kees Cook <keescook@...omium.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rcu@...r.kernel.org, Tejun Heo <tj@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2 2/3] kernel: set taint flag 'L' at any kind of lockup

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@...dex-team.ru>
Acked-by: Paul E. McKenney <paulmck@...nel.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);
 		}
 	}