[LTP] cgroup_regression_test failed in CentOS 7.2

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Dong ZHu" <bluezhudong@gmail.com>
> To: ltp@lists.linux.it
> Sent: Friday, 27 May, 2016 4:25:41 AM
> Subject: [LTP] cgroup_regression_test failed in CentOS 7.2
> 
> Hi All,
> 
> I ran LTP test suite in CentOS 7.2 with kernel 3.10.0-327, test named
> "cgroup_regression_test" Test 3 and Test 5 always failed as below:
> http://pastebin.ubuntu.com/16703246/
> 
> Test 3 failed when execute "mount -t cgroup -o cpu xxx cgroup/"
> Test 5 failed when execute "mount -t cgroup -o $subsys1,$subsys2 xxx cgroup/"
> 
> cpu, hugetlb and perf_event has already been mounted in sys as below:
> http://pastebin.ubuntu.com/16703384/
> 
> So the mount operation will definitely fail in the test.
> 
> I just want to know whether it is the test program issue, and whether it can
> be waived ?

This is known to happen on systemd distros, where systemd mounts specific
subsystems together and LTP test wants to mount just one.

In those cases you should get -EBUSY as described in Documentation/cgroup-v1/cgroups.txt:
"If an active hierarchy with exactly the same set of subsystems already
exists, it will be reused for the new mount. If no existing hierarchy
matches, and any of the requested subsystems are in use in an existing
hierarchy, the mount will fail with -EBUSY. Otherwise, a new hierarchy
is activated, associated with the requested subsystems."

Regards,
Jan