Re: PROBLEM: Kernel OOPS and possible system freeze after concurrent writing to cpufreq/scaling_governor (Resend)

["Robert Schöne" <robert.schoene@tu-dresden.de>]

The bug is still there. Here's my bash history, so that you can be sure I checked it correctly:

git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-git
cd linux-git/
git show 56d07db 
git branch --contains 19c7630
git branch --contains 56d07db
git revert -n 56d07db
make oldconfig
make clean
make -j9 deb-pkg
cd ..
sudo dpkg -i linux-libc-dev_3.16.0-rc6+-2_amd64.deb
sudo dpkg -i linux-image-3.16.0-rc6+_3.16.0-rc6+-2_amd64.deb
sudo dpkg -i linux-headers-3.16.0-rc6+_3.16.0-rc6+-2_amd64.deb
sudo dpkg -i linux-firmware-image-3.16.0-rc6+_3.16.0-rc6+-2_amd64.deb
sudo update-grub2
sudo reboot

Again, I didn't get a backtrace for the error, but only this:

...
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
...


Robert


Am Donnerstag, den 24.07.2014, 15:12 +0530 schrieb Viresh Kumar:
> On 24 July 2014 12:41, Robert Schöne <robert.schoene@tu-dresden.de> wrote:
> > (Resend, because there hasn't been a reply within the last week)
> 
> How did I miss it? Yes its in my inbox. Sorry buddy..
> 
> > crash_governor.sh:
> > #!/bin/sh
> > # this is called concurrently via runme.sh
> > for I in `seq 1000`
> > do
> >         echo ondemand | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
> >         echo userspace | sudo tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
> > done
> >
> > runme.sh:
> > #!/bin/sh
> > # run 8 concurrent instances
> > for I in `seq 8`
> > do
> >         ./crash_governor.sh &
> > done
> >
> > Just run runme.sh and crash your system :)
> 
> Oh, yes. Quite easily I could see that happening :)
> 
> I have pushed a fix earlier for similar issues:
> 19c7630 cpufreq: serialize calls to __cpufreq_governor()
> 
> but was later reverted by Srivatsa:
> 56d07db cpufreq: Remove temporary fix for race between CPU hotplug and
> sysfs-writes
> 
> because we didn't thought about this usecase.
> 
> I propose we get that back. I have tested a revert of 56d07db on
> my setup and didn't see any crash..
> 
> Please see if that works for you as well..
> 
> --
> viresh

-- 

Dipl.-Inf. Robert Schoene
Computer Scientist - R&D Energy Efficient Computing

Technische Universitaet Dresden
Center for Information Services and High Performance Computing
Distributed and Data Intensive Computing
01062 Dresden
Tel.: +49 (351) 463-42483
Fax : +49 (351) 463-37773
E-Mail: Robert.Schoene@tu-dresden.de