Function cpuset_modify_domain

freebsd/kern/kern_cpuset.c:802–873

* Modify the set 'set' to use a copy the domainset provided. Apply this new * mask to restrict all children in the tree. Checks for validity before * applying the changes. */

 * applying the changes.
 */
static int
cpuset_modify_domain(struct cpuset *set, struct domainset *domain)
{
	struct domainlist domains;
	struct domainset temp;
	struct domainset *dset;
	struct cpuset *root;
	int ndomains, needed;
	int error;

	error = priv_check(curthread, PRIV_SCHED_CPUSET);
	if (error)
		return (error);
	/*
	 * In case we are called from within the jail
	 * we do not allow modifying the dedicated root
	 * cpuset of the jail but may still allow to
	 * change child sets.
	 */
	if (jailed(curthread->td_ucred) &&
	    set->cs_flags & CPU_SET_ROOT)
		return (EPERM);
	domainset_freelist_init(&domains, 0);
	domain = domainset_create(domain);
	ndomains = 0;

	mtx_lock_spin(&cpuset_lock);
	for (;;) {
		root = cpuset_getroot(set);
		dset = root->cs_domain;
		/*
		 * Verify that we have access to this set of domains.
		 */
		if (!domainset_valid(dset, domain)) {
			error = EINVAL;
			goto out;
		}
		/*
		 * If applying prefer we keep the current set as the fallback.
		 */
		if (domain->ds_policy == DOMAINSET_POLICY_PREFER)
			DOMAINSET_COPY(&set->cs_domain->ds_mask,
			    &domain->ds_mask);
		/*
		 * Determine whether we can apply this set of domains and
		 * how many new domain structures it will require.
		 */
		domainset_copy(domain, &temp);
		needed = 0;
		error = cpuset_testupdate_domain(set, &temp, set->cs_domain,
		    &needed, 0);
		if (error)
			goto out;
		if (ndomains >= needed)
			break;

		/* Dropping the lock; we'll need to re-evaluate again. */
		mtx_unlock_spin(&cpuset_lock);