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From upstream bug report:


Processors' Idling, as defined in "Processor Aggregator Device" chapter of ACPI
4.0a spec, isn't stable, it doesn't handle big changes of the active cores
well. Slow changes (e.g. 2 cores idled or activated every second) are OK, but
drastic changes of the number of active cores cause whole FW-OS communication
to stop (communication using ACPI defined interface). It happens especially
when bigger number of cores (8 or more) is reactivated.

Version-Release number of selected component (if applicable):
I've tested it using kernel 2.6.32 and newer, e.g. 3.1.4 with the same results.

Reproducible: Always

Steps to Reproduce:
1. Request OS to idle 8 or more cores as described in "Processor Aggregator
Device" chapter of ACPI 4.0a spec.
2. Request OS to make all cores active.
3. Repeat steps with bigger number of cores to idle if necessary.
Actual Results:  
Cores are active again but communication with the firmware using ASL code is
stopped, no _OST response from OS. power_saving processes are hanging.


Expected Results:  
Cores are active again.



Other details:
Patch in upstream bug merged into main line kernel

This is also discussed here: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1035216

and here:
http://en.community.dell.com/support-forums/servers/f/1466/t/19456558.aspx

The latter link offers some workaround possibilities.

This request was not resolved in time for the current release.
Red Hat invites you to ask your support representative to
propose this request, if still desired, for consideration in
the next release of Red Hat Enterprise Linux.

This request was not resolved in time for the current release.
Red Hat invites you to ask your support representative to
propose this request, if still desired, for consideration in
the next release of Red Hat Enterprise Linux.

This Bugzilla has been reviewed by Red Hat and is not planned on being addressed in Red Hat Enterprise Linux 6 and therefore will be closed. If this bug is critical to production systems, please contact your Red Hat support representative and provide sufficient business justification.