Merge tag 'cgroup-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - cpuset changes:

    - Continue separating v1 and v2 implementations by moving more
      v1-specific logic into cpuset-v1.c

    - Improve partition handling. Sibling partitions are no longer
      invalidated on cpuset.cpus conflict, cpuset.cpus changes no longer
      fail in v2, and effective_xcpus computation is made consistent

    - Fix partition effective CPUs overlap that caused a warning on
      cpuset removal when sibling partitions shared CPUs

 - Increase the maximum cgroup subsystem count from 16 to 32 to
   accommodate future subsystem additions

 - Misc cleanups and selftest improvements including switching to
   css_is_online() helper, removing dead code and stale documentation
   references, using lockdep_assert_cpuset_lock_held() consistently, and
   adding polling helpers for asynchronously updated cgroup statistics

* tag 'cgroup-for-6.20' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  cpuset: fix overlap of partition effective CPUs
  cgroup: increase maximum subsystem count from 16 to 32
  cgroup: Remove stale cpu.rt.max reference from documentation
  cpuset: replace direct lockdep_assert_held() with lockdep_assert_cpuset_lock_held()
  cgroup/cpuset: Move the v1 empty cpus/mems check to cpuset1_validate_change()
  cgroup/cpuset: Don't invalidate sibling partitions on cpuset.cpus conflict
  cgroup/cpuset: Don't fail cpuset.cpus change in v2
  cgroup/cpuset: Consistently compute effective_xcpus in update_cpumasks_hier()
  cgroup/cpuset: Streamline rm_siblings_excl_cpus()
  cpuset: remove dead code in cpuset-v1.c
  cpuset: remove v1-specific code from generate_sched_domains
  cpuset: separate generate_sched_domains for v1 and v2
  cpuset: move update_domain_attr_tree to cpuset_v1.c
  cpuset: add cpuset1_init helper for v1 initialization
  cpuset: add cpuset1_online_css helper for v1-specific operations
  cpuset: add lockdep_assert_cpuset_lock_held helper
  cpuset: Remove unnecessary checks in rebuild_sched_domains_locked
  cgroup: switch to css_is_online() helper
  selftests: cgroup: Replace sleep with cg_read_key_long_poll() for waiting on nr_dying_descendants
  selftests: cgroup: make test_memcg_sock robust against delayed sock stats
  ...

1 files changed, 27 insertions, 17 deletions

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 098d6831b3c0..91beaa6798ce 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -737,9 +737,6 @@ combinations are invalid and should be rejected.  Also, if the
 resource is mandatory for execution of processes, process migrations
 may be rejected.
 
-"cpu.rt.max" hard-allocates realtime slices and is an example of this
-type.
-
 
 Interface Files
 ===============
@@ -2561,10 +2558,10 @@ Cpuset Interface Files
 	Users can manually set it to a value that is different from
 	"cpuset.cpus".	One constraint in setting it is that the list of
 	CPUs must be exclusive with respect to "cpuset.cpus.exclusive"
-	of its sibling.  If "cpuset.cpus.exclusive" of a sibling cgroup
-	isn't set, its "cpuset.cpus" value, if set, cannot be a subset
-	of it to leave at least one CPU available when the exclusive
-	CPUs are taken away.
+	and "cpuset.cpus.exclusive.effective" of its siblings.	Another
+	constraint is that it cannot be a superset of "cpuset.cpus"
+	of its sibling in order to leave at least one CPU available to
+	that sibling when the exclusive CPUs are taken away.
 
 	For a parent cgroup, any one of its exclusive CPUs can only
 	be distributed to at most one of its child cgroups.  Having an
@@ -2584,9 +2581,9 @@ Cpuset Interface Files
 	of this file will always be a subset of its parent's
 	"cpuset.cpus.exclusive.effective" if its parent is not the root
 	cgroup.  It will also be a subset of "cpuset.cpus.exclusive"
-	if it is set.  If "cpuset.cpus.exclusive" is not set, it is
-	treated to have an implicit value of "cpuset.cpus" in the
-	formation of local partition.
+	if it is set.  This file should only be non-empty if either
+	"cpuset.cpus.exclusive" is set or when the current cpuset is
+	a valid partition root.
 
   cpuset.cpus.isolated
 	A read-only and root cgroup only multiple values file.
@@ -2618,13 +2615,22 @@ Cpuset Interface Files
 	There are two types of partitions - local and remote.  A local
 	partition is one whose parent cgroup is also a valid partition
 	root.  A remote partition is one whose parent cgroup is not a
-	valid partition root itself.  Writing to "cpuset.cpus.exclusive"
-	is optional for the creation of a local partition as its
-	"cpuset.cpus.exclusive" file will assume an implicit value that
-	is the same as "cpuset.cpus" if it is not set.	Writing the
-	proper "cpuset.cpus.exclusive" values down the cgroup hierarchy
-	before the target partition root is mandatory for the creation
-	of a remote partition.
+	valid partition root itself.
+
+	Writing to "cpuset.cpus.exclusive" is optional for the creation
+	of a local partition as its "cpuset.cpus.exclusive" file will
+	assume an implicit value that is the same as "cpuset.cpus" if it
+	is not set.  Writing the proper "cpuset.cpus.exclusive" values
+	down the cgroup hierarchy before the target partition root is
+	mandatory for the creation of a remote partition.
+
+	Not all the CPUs requested in "cpuset.cpus.exclusive" can be
+	used to form a new partition.  Only those that were present
+	in its parent's "cpuset.cpus.exclusive.effective" control
+	file can be used.  For partitions created without setting
+	"cpuset.cpus.exclusive", exclusive CPUs specified in sibling's
+	"cpuset.cpus.exclusive" or "cpuset.cpus.exclusive.effective"
+	also cannot be used.
 
 	Currently, a remote partition cannot be created under a local
 	partition.  All the ancestors of a remote partition root except
@@ -2632,6 +2638,10 @@ Cpuset Interface Files
 
 	The root cgroup is always a partition root and its state cannot
 	be changed.  All other non-root cgroups start out as "member".
+	Even though the "cpuset.cpus.exclusive*" and "cpuset.cpus"
+	control files are not present in the root cgroup, they are
+	implicitly the same as the "/sys/devices/system/cpu/possible"
+	sysfs file.
 
 	When set to "root", the current cgroup is the root of a new
 	partition or scheduling domain.  The set of exclusive CPUs is