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The CS_CPU_EXCLUSIVE flag is currently set whenever cpuset.cpus.exclusive is set to make sure that the exclusivity test will be run to ensure its exclusiveness. At the same time, this flag can be changed whenever the partition root state is changed. For example, the CS_CPU_EXCLUSIVE flag will be reset whenever a partition root becomes invalid. This makes using CS_CPU_EXCLUSIVE to ensure exclusiveness a bit fragile. The current scheme also makes setting up a cpuset.cpus.exclusive hierarchy to enable remote partition harder as cpuset.cpus.exclusive cannot overlap with any cpuset.cpus of sibling cpusets if their cpuset.cpus.exclusive aren't set. Solve these issues by deferring the setting of CS_CPU_EXCLUSIVE flag until the cpuset become a valid partition root while adding new checks in validate_change() to ensure that cpuset.cpus.exclusive of sibling cpusets cannot overlap. An additional check is also added to validate_change() to make sure that cpuset.cpus of one cpuset cannot be a subset of cpuset.cpus.exclusive of a sibling cpuset to avoid the problem that none of those CPUs will be available when these exclusive CPUs are extracted out to a newly enabled partition root. The Documentation/admin-guide/cgroup-v2.rst file is updated to document the new constraints. Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.