Servers with Intel® Xeon® Processor E5, Intel® Xeon® Processor E5 v2, or Intel® Xeon® Processor E7 v2 and certain versions of Red Hat Enterprise Linux 6 kernels become unresponsive/hung or incur a kernel panic

Issue

The server becomes unresponsive with processes blocked in the uninterruptible state 'D', or it incurs a kernel panic 'hung_task: blocked tasks'. In very rare circumstances the system's kernel can also crash/reboot due to an attempted divide-by-zero. Please see the Diagnostic Steps section for further details about possible symptoms. The issue occurs if all of the following conditions are met.

• A Red Hat Enterprise Linux 6 kernel that contains this change from Red Hat private Bug 765720 is warm booted (for example, via the shutdown -r command):

  [sched] x86: Avoid unnecessary overflow in sched_clock
  

• The kernel is warm booted on a machine with any of the Intel® Xeon® E5, Intel® Xeon® E5 v2, or Intel® Xeon® E7 v2 series processors.

• The kernel is warm booted on a machine that has not been power cycled (hard reset) for a long time (typically more than ~200 days).

Notice that this does not mean that a kernel is affected if it has more than ~200 days uptime. It is the warm boot after ~200 days of 'hardware uptime' that actually triggers the issue. The issue occurs at a random point in time after the warm boot, typically within the range of a few minutes to a few hours.

KVM guests (on RHEL KVM hosts or RHEV-H hypervisors) that configure KVM clock as their clock source by default are not affected by the issue. For other virtualization platforms, please contact the platform vendor.

Red Hat Enterprise Linux 5 kernels that are based on upstream kernel version 2.6.18 are not affected by the issue.

Please see the Environment section for details about the versions of the Red Hat Enterprise Linux 6 kernel that are prone to the issue.