From mboxrd@z Thu Jan  1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 173361] New: Under heavy load, the CPU speed suddenly and
 irreversibly drops from 3500 to 400 MHz
Date: Thu, 29 Sep 2016 14:57:55 +0000
Message-ID: <bug-173361-137361@https.bugzilla.kernel.org/>
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https://bugzilla.kernel.org/show_bug.cgi?id=173361

            Bug ID: 173361
           Summary: Under heavy load, the CPU speed suddenly and
                    irreversibly drops from 3500 to 400 MHz
           Product: Power Management
           Version: 2.5
    Kernel Version: 4.8-rc1
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: cpufreq
          Assignee: linux-pm@vger.kernel.org
          Reporter: Larry.Finger@lwfinger.net
        Regression: No

My Toshiba Tecra A50-A laptop that a CPU described as 'Model: 6.60.3 "Intel(R)
Core(TM) i7-4600M CPU @ 2.90GHz"'. Under heavy load, this dual-core unit with
hyperthreading will suddenly drop from a frequency of 3500 to 410 MHz. The only
way to recover is to reboot. See
http://lkml.iu.edu/hypermail/linux/kernel/1609.3/00720.html for some details
and other discussion.

This bug is being filed under power management because the 'sensors' command
shows the following:

finger@linux-1t8h:~> sensors
coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +88.0°C  (high = +84.0°C, crit = +100.0°C)
Core 0:         +88.0°C  (high = +84.0°C, crit = +100.0°C)
Core 1:         +77.0°C  (high = +84.0°C, crit = +100.0°C)

Routinely, at least one of the CPUs has a temperature higher than the "high"
value. As Rafael Wysocki states "It looks like in 4.8-rc we made a change that
caused the "high" trip point to be acted on." In that case, the bug would be
that the frequency is never restored.

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