softlockup: decouple hung tasks check from softlockup detection

Decoupling allows:

* hung tasks check to happen at very low priority

* hung tasks check and softlockup to be enabled/disabled independently
  at compile and/or run-time

* individual panic settings to be enabled disabled independently
  at compile and/or run-time

* softlockup threshold to be reduced without increasing hung tasks
  poll frequency (hung task check is expensive relative to softlock watchdog)

* hung task check to be zero over-head when disabled at run-time

Signed-off-by: Mandeep Singh Baines <msb@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 38 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 4c9ae6085c75..883ecea22f37 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -186,6 +186,44 @@ config BOOTPARAM_SOFTLOCKUP_PANIC_VALUE
         default 0 if !BOOTPARAM_SOFTLOCKUP_PANIC
         default 1 if BOOTPARAM_SOFTLOCKUP_PANIC
 
+config DETECT_HUNG_TASK
+        bool "Detect Hung Tasks"
+        depends on DEBUG_KERNEL
+        default y
+        help
+          Say Y here to enable the kernel to detect "hung tasks",
+          which are bugs that cause the task to be stuck in
+          uninterruptible "D" state indefinitiley.
+
+          When a hung task is detected, the kernel will print the
+          current stack trace (which you should report), but the
+          task will stay in uninterruptible state. If lockdep is
+          enabled then all held locks will also be reported. This
+          feature has negligible overhead.
+
+config BOOTPARAM_HUNG_TASK_PANIC
+        bool "Panic (Reboot) On Hung Tasks"
+        depends on DETECT_HUNG_TASK
+        help
+          Say Y here to enable the kernel to panic on "hung tasks",
+          which are bugs that cause the kernel to leave a task stuck
+          in uninterruptible "D" state.
+
+          The panic can be used in combination with panic_timeout,
+          to cause the system to reboot automatically after a
+          hung task has been detected. This feature is useful for
+          high-availability systems that have uptime guarantees and
+          where a hung tasks must be resolved ASAP.
+
+          Say N if unsure.
+
+config BOOTPARAM_HUNG_TASK_PANIC_VALUE
+        int
+        depends on DETECT_HUNG_TASK
+        range 0 1
+        default 0 if !BOOTPARAM_HUNG_TASK_PANIC
+        default 1 if BOOTPARAM_HUNG_TASK_PANIC
+
 config SCHED_DEBUG
         bool "Collect scheduler debugging info"
         depends on DEBUG_KERNEL && PROC_FS