This bug has been copied from bug #550724 and has been proposed
to be backported to 6.0 z-stream (EUS).
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.
Technical note added. If any revisions are required, please edit the "Technical Notes" field
accordingly. All revisions will be proofread by the Engineering Content Services team.
In some cases, under a small system load involve some I/O operation, processes started to lock up in the D state (that is, became unresponsive). The system load could in some cases climb steadily. This was due to the way the event channel IRQ (Interrupt Request) was set up. Xen events behave like edge-triggered IRQs, however, the kernel was setting them up as level-triggered IRQs. As a result, any action using Xen event channels could lock up a process in the D state. With this update, the handling has been changed from edge-triggered IRQs to level-triggered IRQs and process no longer lock up in the D state.