[Bug 176411] New: cpufreq/cpuinfo_cur_freq <unknown> for i7 5820k

https://bugzilla.kernel.org/show_bug.cgi?id=176411

            Bug ID: 176411
           Summary: cpufreq/cpuinfo_cur_freq <unknown> for i7 5820k
           Product: Power Management
           Version: 2.5
    Kernel Version: 4.7.6
          Hardware: x86-64
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: cpufreq
          Assignee: linux-pm@vger.kernel.org
          Reporter: mike.d.lui@gmail.com
        Regression: No

# cat /proc/cpuinfo | grep model

model           : 63
model name      : Intel(R) Core(TM) i7-5820K CPU @ 3.30GHz
...

# cat /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_cur_freq

<unknown><unknown><unknown><unknown><unknown><unknown><unknown><unknown><unknown><unknown><unknown><unknown>

# cat /proc/[pid]/stat

will also show '0' for utime, stime, cutime, and cstime

Certain utilities like 'top' and 'ps' will show '0%' for %CPU for a given
process, but not for a given CPU.

I've upgraded my kernel a few times in the past several weeks, and I noticed
this issue before, although I'm not sure the exact kernel version I started
noticing this. This same behavior has been reported for an i7 5930k (also
6-core Haswell-E). Performance degradation that I began noticing around the
same time may be related.

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