Merge tag 'cgroup-for-6.11-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:
"Three patches addressing cpuset corner cases"

* tag 'cgroup-for-6.11-rc4-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: Eliminate unncessary sched domains rebuilds in hotplug
cgroup/cpuset: Clear effective_xcpus on cpus_allowed clearing only if cpus.exclusive not set
cgroup/cpuset: fix panic caused by partcmd_update

kernel/cgroup/cpuset.c

···
 static struct list_head remote_children;
 
 /*
+ * A flag to force sched domain rebuild at the end of an operation while
+ * inhibiting it in the intermediate stages when set. Currently it is only
+ * set in hotplug code.
+ */
+static bool force_sd_rebuild;
+
+/*
  * Partition root states:
  *
  *   0 - member (not a partition root)
···
 			clear_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
 	}
 
-	if (rebuild_domains)
+	if (rebuild_domains && !force_sd_rebuild)
 		rebuild_sched_domains_locked();
 }
 
···
 			remote_partition_disable(child, tmp);
 			disable_cnt++;
 		}
-	if (disable_cnt)
+	if (disable_cnt && !force_sd_rebuild)
 		rebuild_sched_domains_locked();
 }
 
···
 			part_error = PERR_CPUSEMPTY;
 			goto write_error;
 		}
+		/* Check newmask again, whether cpus are available for parent/cs */
+		nocpu |= tasks_nocpu_error(parent, cs, newmask);
 
 		/*
 		 * partcmd_update with newmask:
···
 	}
 	rcu_read_unlock();
 
-	if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD))
+	if (need_rebuild_sched_domains && !(flags & HIER_NO_SD_REBUILD) &&
+	    !force_sd_rebuild)
 		rebuild_sched_domains_locked();
 }
 
···
 	 */
 	if (!*buf) {
 		cpumask_clear(trialcs->cpus_allowed);
-		cpumask_clear(trialcs->effective_xcpus);
+		if (cpumask_empty(trialcs->exclusive_cpus))
+			cpumask_clear(trialcs->effective_xcpus);
 	} else {
 		retval = cpulist_parse(buf, trialcs->cpus_allowed);
 		if (retval < 0)
···
 	cs->flags = trialcs->flags;
 	spin_unlock_irq(&callback_lock);
 
-	if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed)
+	if (!cpumask_empty(trialcs->cpus_allowed) && balance_flag_changed &&
+	    !force_sd_rebuild)
 		rebuild_sched_domains_locked();
 
 	if (spread_flag_changed)
···
 		update_tasks_nodemask(cs);
 }
 
-static bool force_rebuild;
-
 void cpuset_force_rebuild(void)
 {
-	force_rebuild = true;
+	force_sd_rebuild = true;
 }
 
 /**
···
 		       !cpumask_empty(subpartitions_cpus);
 	mems_updated = !nodes_equal(top_cpuset.effective_mems, new_mems);
 
-	/*
-	 * In the rare case that hotplug removes all the cpus in
-	 * subpartitions_cpus, we assumed that cpus are updated.
-	 */
-	if (!cpus_updated && !cpumask_empty(subpartitions_cpus))
-		cpus_updated = true;
-
 	/* For v1, synchronize cpus_allowed to cpu_active_mask */
 	if (cpus_updated) {
+		cpuset_force_rebuild();
 		spin_lock_irq(&callback_lock);
 		if (!on_dfl)
 			cpumask_copy(top_cpuset.cpus_allowed, &new_cpus);
···
 	}
 
 	/* rebuild sched domains if cpus_allowed has changed */
-	if (cpus_updated || force_rebuild) {
-		force_rebuild = false;
+	if (force_sd_rebuild) {
+		force_sd_rebuild = false;
 		rebuild_sched_domains_cpuslocked();
 	}