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, 14 insertions, 1 deletions

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 596dc31a7116..2481ed30d2b5 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -805,6 +805,19 @@ static struct ctl_table kern_table[] = {
                 .extra1         = &neg_one,
                 .extra2         = &sixty,
         },
+#endif
+#ifdef CONFIG_DETECT_HUNG_TASK
+        {
+                .ctl_name       = CTL_UNNUMBERED,
+                .procname       = "hung_task_panic",
+                .data           = &sysctl_hung_task_panic,
+                .maxlen         = sizeof(int),
+                .mode           = 0644,
+                .proc_handler   = &proc_dointvec_minmax,
+                .strategy       = &sysctl_intvec,
+                .extra1         = &zero,
+                .extra2         = &one,
+        },
         {
                 .ctl_name       = CTL_UNNUMBERED,
                 .procname       = "hung_task_check_count",
@@ -820,7 +833,7 @@ static struct ctl_table kern_table[] = {
                 .data           = &sysctl_hung_task_timeout_secs,
                 .maxlen         = sizeof(unsigned long),
                 .mode           = 0644,
-                .proc_handler   = &proc_doulongvec_minmax,
+                .proc_handler   = &proc_dohung_task_timeout_secs,
                 .strategy       = &sysctl_intvec,
         },
         {