hung task: check specific tasks for long uninterruptible sleep state
khungtask by default monitors all tasks for long unterruptible sleep.
This change introduces a sysctl option, /proc/sys/kernel/
hung_task_selective_monitoring, to enable monitoring selected tasks.
If this sysctl option is enabled then only the tasks with
/proc/$PID/hang_detection_enabled set are to be monitored,
otherwise all tasks are monitored as default case.
Some tasks may intentionally moves to uninterruptable sleep state,
which shouldn't leads to khungtask panics, as those are recoverable
hungs. So to avoid false hung reports, add an option to select tasks
to be monitored and report/panic them only.
By default, enable the feature always to monitor selected tasks.
Change-Id: I48cd8cfe73dbe2b577541fe9607190eac5556bb2
Signed-off-by: Imran Khan <kimran@codeaurora.org>
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>
diff --git a/kernel/hung_task.c b/kernel/hung_task.c
index 2b59c82..b94d3d1 100644
--- a/kernel/hung_task.c
+++ b/kernel/hung_task.c
@@ -17,6 +17,7 @@
#include <linux/sysctl.h>
#include <linux/utsname.h>
#include <trace/events/sched.h>
+#include <linux/sched/sysctl.h>
/*
* The number of tasks checked:
@@ -24,6 +25,14 @@
int __read_mostly sysctl_hung_task_check_count = PID_MAX_LIMIT;
/*
+ * Selective monitoring of hung tasks.
+ *
+ * if set to 1, khungtaskd skips monitoring tasks, which has
+ * task_struct->hang_detection_enabled value not set, else monitors all tasks.
+ */
+int sysctl_hung_task_selective_monitoring = 1;
+
+/*
* Limit number of tasks checked in a batch.
*
* This value controls the preemptibility of khungtaskd since preemption
@@ -179,7 +188,10 @@
}
/* use "==" to skip the TASK_KILLABLE tasks waiting on NFS */
if (t->state == TASK_UNINTERRUPTIBLE)
- check_hung_task(t, timeout);
+ /* Check for selective monitoring */
+ if (!sysctl_hung_task_selective_monitoring ||
+ t->hang_detection_enabled)
+ check_hung_task(t, timeout);
}
unlock:
rcu_read_unlock();