How do I use hung task check in RHEL

Solution Verified - Updated -

Issue

  • Can I detect a hung process?
  • What are the following variables? What do these hung task configuration parameters and their values mean and control?

    # sysctl -a --pattern hung
    kernel.hung_task_warnings = 10
    kernel.hung_task_timeout_secs = 120
    kernel.hung_task_check_count = 32768
    kernel.hung_task_panic = 0
    
  • How can I use hung task check?

  • How to automatically collect vmcore when "hung_task_timeout_secs" messages are logged?

    INFO: task <process>:<pid> blocked for more than 120 seconds.  
    "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.  
    
  • How to set 'hung_task_panic' parameter ?

  • When or under what circumstances should I avoid setting 'hung_task_panic'?

  • How can I reduce or disable the number of "task ... blocked for more than N seconds" events being logged?

Environment

  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 5.5 (kernel-2.6.18-194) or above
  • D state (uninterruptible sleep) processes present in system

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