On Thu, May 31, 2018 at 09:25:29AM +0800, Zefan Li wrote:

Hi Waiman,

On 2018/5/30 21:46, Waiman Long wrote:

quoted

It was found that the cpuset.cpus could contain CPUs that are not listed
in their parent's cpu list as shown by the command sequence below:

  # echo "+cpuset" >cgroup.subtree_control
  # mkdir g1
  # echo 0-5 >g1/cpuset.cpus
  # mkdir g1/g11
  # echo "+cpuset" > g1/cgroup.subtree_control
  # echo 6-11 >g1/g11/cpuset.cpus
  # grep -R . g1 | grep "\.cpus"
  g1/cpuset.cpus:0-5
  g1/cpuset.cpus.effective:0-5
  g1/g11/cpuset.cpus:6-11
  g1/g11/cpuset.cpus.effective:0-5

As the intersection of g11's cpus and that of g1 is empty, the effective
cpus of g11 is just that of g1. The check in update_cpumask() is now
corrected to make sure that cpus in a child cpus must be a subset of
its parent's cpus. The error "write error: Invalid argument" will now
be reported in the above case.

We made the distinction between user-configured CPUs and effective CPUs
in commit 7e88291beefbb758, so actually it's not a bug.

Why though; that makes no sense what so ever.
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