Processes block for long periods when trying to read `/proc/$PID/cmdline` under heavy load on RHEL6

Solution Verified - Updated -

Issue

  • The server crashed unexpectedly
  • When disk load becomes very high processes may block trying to read the contents of a /proc/$PID/cmdline file.
    • This can cripple use of management tools such as "top", "ps", etc.

Environment

  • Red Hat Enterprise Linux 6
    • It is currently suspected that only kernels later than 2.6.32-220.el6 are affected.
    • Issue reported on kernels 2.6.32-279.el6, 2.6.32-358.6.2.el6 and 2.6.32-431.53.2 so far.
  • Issue my be triggered by monitoring software such as HP health (cmahostd), or any tool that reads /proc/<pid>/cmdline.

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