RE: System will not suspend with highest numbered CPU offline [REGRESSION][BISECTED]

["Doug Smythies" <dsmythies@telus.net>]

On 2015.09.04 08:00 Rafael J. Wysocki wrote:
> On Thursday, September 03, 2015 02:40:43 PM Doug Smythies wrote:
>> As of, or about, Kernel 4.2RC1 if I take my highest numbered
>> CPU offline (7 in my case), the system will not suspend.

> Does "will not suspend" mean that the suspend will fail with an error
> or will it crash or hang or something else?

Something else: Nothing at all happens, no error, no crash, no hang,
no log entries (at least that I have been able to find).
I use the "sudo pm-suspend" command, and it is as if it is a no-op.

doug@s15:/sys/devices/system/cpu$ cat /sys/devices/system/cpu/cpu*/online
1
1
1
1
1
1
0

Someone suggested to me that I have to take the core offline, not just
the 1 of 2 CPUs on the same core. However it makes no difference, and
CPU 3 offline by itself works fine.

>> The issue persists through Kernel 4.2.
>> This is on my test computer with an i7-2600K.
>> I do not normally use suspend on this computer,
>> but was doing so while working on a bug report.
>> 
>> The kernel was bisected, and the result was:
>> 
>> $ git bisect bad
>> 87549141d516aee71d511138e27117c41e8aef68 is the first bad commit
>> commit 87549141d516aee71d511138e27117c41e8aef68
>> Author: Viresh Kumar <viresh.kumar@linaro.org>
>> Date:   Wed Jun 10 02:13:21 2015 +0200
>> 
>> cpufreq: Stop migrating sysfs files on hotplug
>> 
>> See also several e-mails with the above subject line
>> between June 8th and 10th.
>> 
>> With any other combination of taking CPUs offline,
>> not including CPU 7, suspend seems to work properly.

> Well, we'll need to debug it some.
> Can you please check what's in the
> /sys/devices/system/cpu/cpuX/cpufreq/related_cpus
> files for all CPUs on your system?

doug@s15:/sys/devices/system/cpu$ cat cpu?/cpufreq/related_cpus
0
1
2
3
4
5
6
7