Red Hat Bugzilla – Bug 165384
cpufreq driver hangs when using SMP Powernow
Last modified: 2007-11-30 17:07:19 EST
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Description of problem:
The cpufreq driver works for a while but eventually hangs on systems using SMP Powernow. cpufreq.c has many SMP enablement fixes upstream such as per-cpu reference count, etc that are likely required for SMP powernow.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. modprobe powernow-k8 on an SMP Powernow capable system
2. start cpuspeed
3. kill cpuspeed when hung (it wont die... now a zombie)
Actual Results: cpuspeed runs for a while but eventually hangs (strace reveals it hangs when trying to read from a cpufreq related file in /sys). cpuspeed never gets a chance to update CPU frequencies (this hang happens in the first 60 seconds). cpuspeed hangs and cant be killed. any process that read/writes to these files in /sys hang as well.
Expected Results: cpuspeed should shift between frequencies and keep running. reading and writing to the cpuspeed specific /sys files should not cause a process to hang. cpuspeed should die if killed.
this should be a MUSTFIX for U2 being that we wont have SMP Powernow enablement
without these enhancements
Created attachment 117656 [details]
patch to resolve cpuspeed (cpufreq+powernow-k8) hang
this patch was posted on 8/11/05 to rhkernel
Incremental patch to powernow-k8 v1.39 driver update BZ 160011
Some vendor testing exposed a few loose ends in the Powernow driver update,
specifically the cpuspeed daemon hanging and the ondemand and powersave
governor drivers failing to load. The problem was that the powernow-k8 module
was getting stuck in a few spots, causing the cpufreq module to hang, and thus
causing the cpuspeed daemon to hang (cpuspeed couldnt be killed once hung
This patch resolves these issues as well as removing 1 unused variable (code
I did confirm that powernow-k8 now works correctly on SMP machines, cpuspeed no
longer hangs, and the ondemand and powersave modules now load as well.
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 the 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.