kern_cpuset.c

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/*-
 * Copyright (c) 2008,  Jeffrey Roberson <jeff@freebsd.org>
 * All rights reserved.
 * 
 * Copyright (c) 2008 Nokia Corporation
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/sysproto.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/refcount.h>
#include <sys/sched.h>
#include <sys/smp.h>
#include <sys/syscallsubr.h>
#include <sys/cpuset.h>
#include <sys/sx.h>
#include <sys/queue.h>
#include <sys/libkern.h>
#include <sys/limits.h>
#include <sys/bus.h>
#include <sys/interrupt.h>

#include <vm/uma.h>

#ifdef DDB
#include <ddb/ddb.h>
#endif /* DDB */

/*
 * cpusets provide a mechanism for creating and manipulating sets of
 * processors for the purpose of constraining the scheduling of threads to
 * specific processors.
 *
 * Each process belongs to an identified set, by default this is set 1.  Each
 * thread may further restrict the cpus it may run on to a subset of this
 * named set.  This creates an anonymous set which other threads and processes
 * may not join by number.
 *
 * The named set is referred to herein as the 'base' set to avoid ambiguity.
 * This set is usually a child of a 'root' set while the anonymous set may
 * simply be referred to as a mask.  In the syscall api these are referred to
 * as the ROOT, CPUSET, and MASK levels where CPUSET is called 'base' here.
 *
 * Threads inherit their set from their creator whether it be anonymous or
 * not.  This means that anonymous sets are immutable because they may be
 * shared.  To modify an anonymous set a new set is created with the desired
 * mask and the same parent as the existing anonymous set.  This gives the
 * illusion of each thread having a private mask.
 *
 * Via the syscall apis a user may ask to retrieve or modify the root, base,
 * or mask that is discovered via a pid, tid, or setid.  Modifying a set
 * modifies all numbered and anonymous child sets to comply with the new mask.
 * Modifying a pid or tid's mask applies only to that tid but must still
 * exist within the assigned parent set.
 *
 * A thread may not be assigned to a group separate from other threads in
 * the process.  This is to remove ambiguity when the setid is queried with
 * a pid argument.  There is no other technical limitation.
 *
 * This somewhat complex arrangement is intended to make it easy for
 * applications to query available processors and bind their threads to
 * specific processors while also allowing administrators to dynamically
 * reprovision by changing sets which apply to groups of processes.
 *
 * A simple application should not concern itself with sets at all and
 * rather apply masks to its own threads via CPU_WHICH_TID and a -1 id
 * meaning 'curthread'.  It may query available cpus for that tid with a
 * getaffinity call using (CPU_LEVEL_CPUSET, CPU_WHICH_PID, -1, ...).
 */
static uma_zone_t cpuset_zone;
static struct mtx cpuset_lock;
static struct setlist cpuset_ids;
static struct unrhdr *cpuset_unr;
static struct cpuset *cpuset_zero;

/* Return the size of cpuset_t at the kernel level */
SYSCTL_INT(_kern_sched, OID_AUTO, cpusetsize, CTLFLAG_RD,
    SYSCTL_NULL_INT_PTR, sizeof(cpuset_t), "sizeof(cpuset_t)");

cpuset_t *cpuset_root;

/*
 * Acquire a reference to a cpuset, all pointers must be tracked with refs.
 */
struct cpuset *
cpuset_ref(struct cpuset *set)
{

        refcount_acquire(&set->cs_ref);
        return (set);
}

/*
 * Walks up the tree from 'set' to find the root.  Returns the root
 * referenced.
 */
static struct cpuset *
cpuset_refroot(struct cpuset *set)
{

        for (; set->cs_parent != NULL; set = set->cs_parent)
                if (set->cs_flags & CPU_SET_ROOT)
                        break;
        cpuset_ref(set);

        return (set);
}

/*
 * Find the first non-anonymous set starting from 'set'.  Returns this set
 * referenced.  May return the passed in set with an extra ref if it is
 * not anonymous. 
 */
static struct cpuset *
cpuset_refbase(struct cpuset *set)
{

        if (set->cs_id == CPUSET_INVALID)
                set = set->cs_parent;
        cpuset_ref(set);

        return (set);
}

/*
 * Release a reference in a context where it is safe to allocate.
 */
void
cpuset_rel(struct cpuset *set)
{
        cpusetid_t id;

        if (refcount_release(&set->cs_ref) == 0)
                return;
        mtx_lock_spin(&cpuset_lock);
        LIST_REMOVE(set, cs_siblings);
        id = set->cs_id;
        if (id != CPUSET_INVALID)
                LIST_REMOVE(set, cs_link);
        mtx_unlock_spin(&cpuset_lock);
        cpuset_rel(set->cs_parent);
        uma_zfree(cpuset_zone, set);
        if (id != CPUSET_INVALID)
                free_unr(cpuset_unr, id);
}

/*
 * Deferred release must be used when in a context that is not safe to
 * allocate/free.  This places any unreferenced sets on the list 'head'.
 */
static void
cpuset_rel_defer(struct setlist *head, struct cpuset *set)
{

        if (refcount_release(&set->cs_ref) == 0)
                return;
        mtx_lock_spin(&cpuset_lock);
        LIST_REMOVE(set, cs_siblings);
        if (set->cs_id != CPUSET_INVALID)
                LIST_REMOVE(set, cs_link);
        LIST_INSERT_HEAD(head, set, cs_link);
        mtx_unlock_spin(&cpuset_lock);
}

/*
 * Complete a deferred release.  Removes the set from the list provided to
 * cpuset_rel_defer.
 */
static void
cpuset_rel_complete(struct cpuset *set)
{
        LIST_REMOVE(set, cs_link);
        cpuset_rel(set->cs_parent);
        uma_zfree(cpuset_zone, set);
}

/*
 * Find a set based on an id.  Returns it with a ref.
 */
static struct cpuset *
cpuset_lookup(cpusetid_t setid, struct thread *td)
{
        struct cpuset *set;

        if (setid == CPUSET_INVALID)
                return (NULL);
        mtx_lock_spin(&cpuset_lock);
        LIST_FOREACH(set, &cpuset_ids, cs_link)
                if (set->cs_id == setid)
                        break;
        if (set)
                cpuset_ref(set);
        mtx_unlock_spin(&cpuset_lock);

        KASSERT(td != NULL, ("[%s:%d] td is NULL", __func__, __LINE__));
        if (set != NULL && jailed(td->td_ucred)) {
                struct cpuset *jset, *tset;

                jset = td->td_ucred->cr_prison->pr_cpuset;
                for (tset = set; tset != NULL; tset = tset->cs_parent)
                        if (tset == jset)
                                break;
                if (tset == NULL) {
                        cpuset_rel(set);
                        set = NULL;
                }
        }

        return (set);
}

/*
 * Create a set in the space provided in 'set' with the provided parameters.
 * The set is returned with a single ref.  May return EDEADLK if the set
 * will have no valid cpu based on restrictions from the parent.
 */
static int
_cpuset_create(struct cpuset *set, struct cpuset *parent, const cpuset_t *mask,
    cpusetid_t id)
{

        if (!CPU_OVERLAP(&parent->cs_mask, mask))
                return (EDEADLK);
        CPU_COPY(mask, &set->cs_mask);
        LIST_INIT(&set->cs_children);
        refcount_init(&set->cs_ref, 1);
        set->cs_flags = 0;
        mtx_lock_spin(&cpuset_lock);
        CPU_AND(&set->cs_mask, &parent->cs_mask);
        set->cs_id = id;
        set->cs_parent = cpuset_ref(parent);
        LIST_INSERT_HEAD(&parent->cs_children, set, cs_siblings);
        if (set->cs_id != CPUSET_INVALID)
                LIST_INSERT_HEAD(&cpuset_ids, set, cs_link);
        mtx_unlock_spin(&cpuset_lock);

        return (0);
}

/*
 * Create a new non-anonymous set with the requested parent and mask.  May
 * return failures if the mask is invalid or a new number can not be
 * allocated.
 */
static int
cpuset_create(struct cpuset **setp, struct cpuset *parent, const cpuset_t *mask)
{
        struct cpuset *set;
        cpusetid_t id;
        int error;

        id = alloc_unr(cpuset_unr);
        if (id == -1)
                return (ENFILE);
        *setp = set = uma_zalloc(cpuset_zone, M_WAITOK);
        error = _cpuset_create(set, parent, mask, id);
        if (error == 0)
                return (0);
        free_unr(cpuset_unr, id);
        uma_zfree(cpuset_zone, set);

        return (error);
}

/*
 * Recursively check for errors that would occur from applying mask to
 * the tree of sets starting at 'set'.  Checks for sets that would become
 * empty as well as RDONLY flags.
 */
static int
cpuset_testupdate(struct cpuset *set, cpuset_t *mask, int check_mask)
{
        struct cpuset *nset;
        cpuset_t newmask;
        int error;

        mtx_assert(&cpuset_lock, MA_OWNED);
        if (set->cs_flags & CPU_SET_RDONLY)
                return (EPERM);
        if (check_mask) {
                if (!CPU_OVERLAP(&set->cs_mask, mask))
                        return (EDEADLK);
                CPU_COPY(&set->cs_mask, &newmask);
                CPU_AND(&newmask, mask);
        } else
                CPU_COPY(mask, &newmask);
        error = 0;
        LIST_FOREACH(nset, &set->cs_children, cs_siblings) 
                if ((error = cpuset_testupdate(nset, &newmask, 1)) != 0)
                        break;
        return (error);
}

/*
 * Applies the mask 'mask' without checking for empty sets or permissions.
 */
static void
cpuset_update(struct cpuset *set, cpuset_t *mask)
{
        struct cpuset *nset;

        mtx_assert(&cpuset_lock, MA_OWNED);
        CPU_AND(&set->cs_mask, mask);
        LIST_FOREACH(nset, &set->cs_children, cs_siblings) 
                cpuset_update(nset, &set->cs_mask);

        return;
}

/*
 * Modify the set 'set' to use a copy of the mask provided.  Apply this new
 * mask to restrict all children in the tree.  Checks for validity before
 * applying the changes.
 */
static int
cpuset_modify(struct cpuset *set, cpuset_t *mask)
{
        struct cpuset *root;
        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);
        /*
         * Verify that we have access to this set of
         * cpus.
         */
        root = set->cs_parent;
        if (root && !CPU_SUBSET(&root->cs_mask, mask))
                return (EINVAL);
        mtx_lock_spin(&cpuset_lock);
        error = cpuset_testupdate(set, mask, 0);
        if (error)
                goto out;
        CPU_COPY(mask, &set->cs_mask);
        cpuset_update(set, mask);
out:
        mtx_unlock_spin(&cpuset_lock);

        return (error);
}

/*
 * Resolve the 'which' parameter of several cpuset apis.
 *
 * For WHICH_PID and WHICH_TID return a locked proc and valid proc/tid.  Also
 * checks for permission via p_cansched().
 *
 * For WHICH_SET returns a valid set with a new reference.
 *
 * -1 may be supplied for any argument to mean the current proc/thread or
 * the base set of the current thread.  May fail with ESRCH/EPERM.
 */
static int
cpuset_which(cpuwhich_t which, id_t id, struct proc **pp, struct thread **tdp,
    struct cpuset **setp)
{
        struct cpuset *set;
        struct thread *td;
        struct proc *p;
        int error;

        *pp = p = NULL;
        *tdp = td = NULL;
        *setp = set = NULL;
        switch (which) {
        case CPU_WHICH_PID:
                if (id == -1) {
                        PROC_LOCK(curproc);
                        p = curproc;
                        break;
                }
                if ((p = pfind(id)) == NULL)
                        return (ESRCH);
                break;
        case CPU_WHICH_TID:
                if (id == -1) {
                        PROC_LOCK(curproc);
                        p = curproc;
                        td = curthread;
                        break;
                }
                td = tdfind(id, -1);
                if (td == NULL)
                        return (ESRCH);
                p = td->td_proc;
                break;
        case CPU_WHICH_CPUSET:
                if (id == -1) {
                        thread_lock(curthread);
                        set = cpuset_refbase(curthread->td_cpuset);
                        thread_unlock(curthread);
                } else
                        set = cpuset_lookup(id, curthread);
                if (set) {
                        *setp = set;
                        return (0);
                }
                return (ESRCH);
        case CPU_WHICH_JAIL:
        {
                /* Find `set' for prison with given id. */
                struct prison *pr;

                sx_slock(&allprison_lock);
                pr = prison_find_child(curthread->td_ucred->cr_prison, id);
                sx_sunlock(&allprison_lock);
                if (pr == NULL)
                        return (ESRCH);
                cpuset_ref(pr->pr_cpuset);
                *setp = pr->pr_cpuset;
                mtx_unlock(&pr->pr_mtx);
                return (0);
        }
        case CPU_WHICH_IRQ:
                return (0);
        default:
                return (EINVAL);
        }
        error = p_cansched(curthread, p);
        if (error) {
                PROC_UNLOCK(p);
                return (error);
        }
        if (td == NULL)
                td = FIRST_THREAD_IN_PROC(p);
        *pp = p;
        *tdp = td;
        return (0);
}

/*
 * Create an anonymous set with the provided mask in the space provided by
 * 'fset'.  If the passed in set is anonymous we use its parent otherwise
 * the new set is a child of 'set'.
 */
static int
cpuset_shadow(struct cpuset *set, struct cpuset *fset, const cpuset_t *mask)
{
        struct cpuset *parent;

        if (set->cs_id == CPUSET_INVALID)
                parent = set->cs_parent;
        else
                parent = set;
        if (!CPU_SUBSET(&parent->cs_mask, mask))
                return (EDEADLK);
        return (_cpuset_create(fset, parent, mask, CPUSET_INVALID));
}

/*
 * Handle two cases for replacing the base set or mask of an entire process.
 *
 * 1) Set is non-null and mask is null.  This reparents all anonymous sets
 *    to the provided set and replaces all non-anonymous td_cpusets with the
 *    provided set.
 * 2) Mask is non-null and set is null.  This replaces or creates anonymous
 *    sets for every thread with the existing base as a parent.
 *
 * This is overly complicated because we can't allocate while holding a 
 * spinlock and spinlocks must be held while changing and examining thread
 * state.
 */
static int
cpuset_setproc(pid_t pid, struct cpuset *set, cpuset_t *mask)
{
        struct setlist freelist;
        struct setlist droplist;
        struct cpuset *tdset;
        struct cpuset *nset;
        struct thread *td;
        struct proc *p;
        int threads;
        int nfree;
        int error;
        /*
         * The algorithm requires two passes due to locking considerations.
         * 
         * 1) Lookup the process and acquire the locks in the required order.
         * 2) If enough cpusets have not been allocated release the locks and
         *    allocate them.  Loop.
         */
        LIST_INIT(&freelist);
        LIST_INIT(&droplist);
        nfree = 0;
        for (;;) {
                error = cpuset_which(CPU_WHICH_PID, pid, &p, &td, &nset);
                if (error)
                        goto out;
                if (nfree >= p->p_numthreads)
                        break;
                threads = p->p_numthreads;
                PROC_UNLOCK(p);
                for (; nfree < threads; nfree++) {
                        nset = uma_zalloc(cpuset_zone, M_WAITOK);
                        LIST_INSERT_HEAD(&freelist, nset, cs_link);
                }
        }
        PROC_LOCK_ASSERT(p, MA_OWNED);
        /*
         * Now that the appropriate locks are held and we have enough cpusets,
         * make sure the operation will succeed before applying changes.  The
         * proc lock prevents td_cpuset from changing between calls.
         */
        error = 0;
        FOREACH_THREAD_IN_PROC(p, td) {
                thread_lock(td);
                tdset = td->td_cpuset;
                /*
                 * Verify that a new mask doesn't specify cpus outside of
                 * the set the thread is a member of.
                 */
                if (mask) {
                        if (tdset->cs_id == CPUSET_INVALID)
                                tdset = tdset->cs_parent;
                        if (!CPU_SUBSET(&tdset->cs_mask, mask))
                                error = EDEADLK;
                /*
                 * Verify that a new set won't leave an existing thread
                 * mask without a cpu to run on.  It can, however, restrict
                 * the set.
                 */
                } else if (tdset->cs_id == CPUSET_INVALID) {
                        if (!CPU_OVERLAP(&set->cs_mask, &tdset->cs_mask))
                                error = EDEADLK;
                }
                thread_unlock(td);
                if (error)
                        goto unlock_out;
        }
        /*
         * Replace each thread's cpuset while using deferred release.  We
         * must do this because the thread lock must be held while operating
         * on the thread and this limits the type of operations allowed.
         */
        FOREACH_THREAD_IN_PROC(p, td) {
                thread_lock(td);
                /*
                 * If we presently have an anonymous set or are applying a
                 * mask we must create an anonymous shadow set.  That is
                 * either parented to our existing base or the supplied set.
                 *
                 * If we have a base set with no anonymous shadow we simply
                 * replace it outright.
                 */
                tdset = td->td_cpuset;
                if (tdset->cs_id == CPUSET_INVALID || mask) {
                        nset = LIST_FIRST(&freelist);
                        LIST_REMOVE(nset, cs_link);
                        if (mask)
                                error = cpuset_shadow(tdset, nset, mask);
                        else
                                error = _cpuset_create(nset, set,
                                    &tdset->cs_mask, CPUSET_INVALID);
                        if (error) {
                                LIST_INSERT_HEAD(&freelist, nset, cs_link);
                                thread_unlock(td);
                                break;
                        }
                } else
                        nset = cpuset_ref(set);
                cpuset_rel_defer(&droplist, tdset);
                td->td_cpuset = nset;
                sched_affinity(td);
                thread_unlock(td);
        }
unlock_out:
        PROC_UNLOCK(p);
out:
        while ((nset = LIST_FIRST(&droplist)) != NULL)
                cpuset_rel_complete(nset);
        while ((nset = LIST_FIRST(&freelist)) != NULL) {
                LIST_REMOVE(nset, cs_link);
                uma_zfree(cpuset_zone, nset);
        }
        return (error);
}

/*
 * Calculate the ffs() of the cpuset.
 */
int
cpusetobj_ffs(const cpuset_t *set)
{
        size_t i;
        int cbit;

        cbit = 0;
        for (i = 0; i < _NCPUWORDS; i++) {
                if (set->__bits[i] != 0) {
                        cbit = ffsl(set->__bits[i]);
                        cbit += i * _NCPUBITS;
                        break;
                }
        }
        return (cbit);
}

/*
 * Return a string representing a valid layout for a cpuset_t object.
 * It expects an incoming buffer at least sized as CPUSETBUFSIZ.
 */
char *
cpusetobj_strprint(char *buf, const cpuset_t *set)
{
        char *tbuf;
        size_t i, bytesp, bufsiz;

        tbuf = buf;
        bytesp = 0;
        bufsiz = CPUSETBUFSIZ;

        for (i = _NCPUWORDS - 1; i > 0; i--) {
                bytesp = snprintf(tbuf, bufsiz, "%lx, ", set->__bits[i]);
                bufsiz -= bytesp;
                tbuf += bytesp;
        }
        snprintf(tbuf, bufsiz, "%lx", set->__bits[0]);
        return (buf);
}

/*
 * Build a valid cpuset_t object from a string representation.
 * It expects an incoming buffer at least sized as CPUSETBUFSIZ.
 */
int
cpusetobj_strscan(cpuset_t *set, const char *buf)
{
        u_int nwords;
        int i, ret;

        if (strlen(buf) > CPUSETBUFSIZ - 1)
                return (-1);

        /* Allow to pass a shorter version of the mask when necessary. */
        nwords = 1;
        for (i = 0; buf[i] != '\0'; i++)
                if (buf[i] == ',')
                        nwords++;
        if (nwords > _NCPUWORDS)
                return (-1);

        CPU_ZERO(set);
        for (i = nwords - 1; i > 0; i--) {
                ret = sscanf(buf, "%lx, ", &set->__bits[i]);
                if (ret == 0 || ret == -1)
                        return (-1);
                buf = strstr(buf, " ");
                if (buf == NULL)
                        return (-1);
                buf++;
        }
        ret = sscanf(buf, "%lx", &set->__bits[0]);
        if (ret == 0 || ret == -1)
                return (-1);
        return (0);
}

/*
 * Apply an anonymous mask to a single thread.
 */
int
cpuset_setthread(lwpid_t id, cpuset_t *mask)
{
        struct cpuset *nset;
        struct cpuset *set;
        struct thread *td;
        struct proc *p;
        int error;

        nset = uma_zalloc(cpuset_zone, M_WAITOK);
        error = cpuset_which(CPU_WHICH_TID, id, &p, &td, &set);
        if (error)
                goto out;
        set = NULL;
        thread_lock(td);
        error = cpuset_shadow(td->td_cpuset, nset, mask);
        if (error == 0) {
                set = td->td_cpuset;
                td->td_cpuset = nset;
                sched_affinity(td);
                nset = NULL;
        }
        thread_unlock(td);
        PROC_UNLOCK(p);
        if (set)
                cpuset_rel(set);
out:
        if (nset)
                uma_zfree(cpuset_zone, nset);
        return (error);
}

/*
 * Creates the cpuset for thread0.  We make two sets:
 * 
 * 0 - The root set which should represent all valid processors in the
 *     system.  It is initially created with a mask of all processors
 *     because we don't know what processors are valid until cpuset_init()
 *     runs.  This set is immutable.
 * 1 - The default set which all processes are a member of until changed.
 *     This allows an administrator to move all threads off of given cpus to
 *     dedicate them to high priority tasks or save power etc.
 */
struct cpuset *
cpuset_thread0(void)
{
        struct cpuset *set;
        int error;

        cpuset_zone = uma_zcreate("cpuset", sizeof(struct cpuset), NULL, NULL,
            NULL, NULL, UMA_ALIGN_PTR, 0);
        mtx_init(&cpuset_lock, "cpuset", NULL, MTX_SPIN | MTX_RECURSE);
        /*
         * Create the root system set for the whole machine.  Doesn't use
         * cpuset_create() due to NULL parent.
         */
        set = uma_zalloc(cpuset_zone, M_WAITOK | M_ZERO);
        CPU_FILL(&set->cs_mask);
        LIST_INIT(&set->cs_children);
        LIST_INSERT_HEAD(&cpuset_ids, set, cs_link);
        set->cs_ref = 1;
        set->cs_flags = CPU_SET_ROOT;
        cpuset_zero = set;
        cpuset_root = &set->cs_mask;
        /*
         * Now derive a default, modifiable set from that to give out.
         */
        set = uma_zalloc(cpuset_zone, M_WAITOK);
        error = _cpuset_create(set, cpuset_zero, &cpuset_zero->cs_mask, 1);
        KASSERT(error == 0, ("Error creating default set: %d\n", error));
        /*
         * Initialize the unit allocator. 0 and 1 are allocated above.
         */
        cpuset_unr = new_unrhdr(2, INT_MAX, NULL);

        return (set);
}

/*
 * Create a cpuset, which would be cpuset_create() but
 * mark the new 'set' as root.
 *
 * We are not going to reparent the td to it.  Use cpuset_setproc_update_set()
 * for that.
 *
 * In case of no error, returns the set in *setp locked with a reference.
 */
int
cpuset_create_root(struct prison *pr, struct cpuset **setp)
{
        struct cpuset *set;
        int error;

        KASSERT(pr != NULL, ("[%s:%d] invalid pr", __func__, __LINE__));
        KASSERT(setp != NULL, ("[%s:%d] invalid setp", __func__, __LINE__));

        error = cpuset_create(setp, pr->pr_cpuset, &pr->pr_cpuset->cs_mask);
        if (error)
                return (error);

        KASSERT(*setp != NULL, ("[%s:%d] cpuset_create returned invalid data",
            __func__, __LINE__));

        /* Mark the set as root. */
        set = *setp;
        set->cs_flags |= CPU_SET_ROOT;

        return (0);
}

int
cpuset_setproc_update_set(struct proc *p, struct cpuset *set)
{
        int error;

        KASSERT(p != NULL, ("[%s:%d] invalid proc", __func__, __LINE__));
        KASSERT(set != NULL, ("[%s:%d] invalid set", __func__, __LINE__));

        cpuset_ref(set);
        error = cpuset_setproc(p->p_pid, set, NULL);
        if (error)
                return (error);
        cpuset_rel(set);
        return (0);
}

/*
 * This is called once the final set of system cpus is known.  Modifies
 * the root set and all children and mark the root read-only.  
 */
static void
cpuset_init(void *arg)
{
        cpuset_t mask;

        mask = all_cpus;
        if (cpuset_modify(cpuset_zero, &mask))
                panic("Can't set initial cpuset mask.\n");
        cpuset_zero->cs_flags |= CPU_SET_RDONLY;
}
SYSINIT(cpuset, SI_SUB_SMP, SI_ORDER_ANY, cpuset_init, NULL);

#ifndef _SYS_SYSPROTO_H_
struct cpuset_args {
        cpusetid_t      *setid;
};
#endif
int
sys_cpuset(struct thread *td, struct cpuset_args *uap)
{
        struct cpuset *root;
        struct cpuset *set;
        int error;

        thread_lock(td);
        root = cpuset_refroot(td->td_cpuset);
        thread_unlock(td);
        error = cpuset_create(&set, root, &root->cs_mask);
        cpuset_rel(root);
        if (error)
                return (error);
        error = copyout(&set->cs_id, uap->setid, sizeof(set->cs_id));
        if (error == 0)
                error = cpuset_setproc(-1, set, NULL);
        cpuset_rel(set);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct cpuset_setid_args {
        cpuwhich_t      which;
        id_t            id;
        cpusetid_t      setid;
};
#endif
int
sys_cpuset_setid(struct thread *td, struct cpuset_setid_args *uap)
{
        struct cpuset *set;
        int error;

        /*
         * Presently we only support per-process sets.
         */
        if (uap->which != CPU_WHICH_PID)
                return (EINVAL);
        set = cpuset_lookup(uap->setid, td);
        if (set == NULL)
                return (ESRCH);
        error = cpuset_setproc(uap->id, set, NULL);
        cpuset_rel(set);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct cpuset_getid_args {
        cpulevel_t      level;
        cpuwhich_t      which;
        id_t            id;
        cpusetid_t      *setid;
#endif
int
sys_cpuset_getid(struct thread *td, struct cpuset_getid_args *uap)
{
        struct cpuset *nset;
        struct cpuset *set;
        struct thread *ttd;
        struct proc *p;
        cpusetid_t id;
        int error;

        if (uap->level == CPU_LEVEL_WHICH && uap->which != CPU_WHICH_CPUSET)
                return (EINVAL);
        error = cpuset_which(uap->which, uap->id, &p, &ttd, &set);
        if (error)
                return (error);
        switch (uap->which) {
        case CPU_WHICH_TID:
        case CPU_WHICH_PID:
                thread_lock(ttd);
                set = cpuset_refbase(ttd->td_cpuset);
                thread_unlock(ttd);
                PROC_UNLOCK(p);
                break;
        case CPU_WHICH_CPUSET:
        case CPU_WHICH_JAIL:
                break;
        case CPU_WHICH_IRQ:
                return (EINVAL);
        }
        switch (uap->level) {
        case CPU_LEVEL_ROOT:
                nset = cpuset_refroot(set);
                cpuset_rel(set);
                set = nset;
                break;
        case CPU_LEVEL_CPUSET:
                break;
        case CPU_LEVEL_WHICH:
                break;
        }
        id = set->cs_id;
        cpuset_rel(set);
        if (error == 0)
                error = copyout(&id, uap->setid, sizeof(id));

        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct cpuset_getaffinity_args {
        cpulevel_t      level;
        cpuwhich_t      which;
        id_t            id;
        size_t          cpusetsize;
        cpuset_t        *mask;
};
#endif
int
sys_cpuset_getaffinity(struct thread *td, struct cpuset_getaffinity_args *uap)
{
        struct thread *ttd;
        struct cpuset *nset;
        struct cpuset *set;
        struct proc *p;
        cpuset_t *mask;
        int error;
        size_t size;

        if (uap->cpusetsize < sizeof(cpuset_t) ||
            uap->cpusetsize > CPU_MAXSIZE / NBBY)
                return (ERANGE);
        size = uap->cpusetsize;
        mask = malloc(size, M_TEMP, M_WAITOK | M_ZERO);
        error = cpuset_which(uap->which, uap->id, &p, &ttd, &set);
        if (error)
                goto out;
        switch (uap->level) {
        case CPU_LEVEL_ROOT:
        case CPU_LEVEL_CPUSET:
                switch (uap->which) {
                case CPU_WHICH_TID:
                case CPU_WHICH_PID:
                        thread_lock(ttd);
                        set = cpuset_ref(ttd->td_cpuset);
                        thread_unlock(ttd);
                        break;
                case CPU_WHICH_CPUSET:
                case CPU_WHICH_JAIL:
                        break;
                case CPU_WHICH_IRQ:
                        error = EINVAL;
                        goto out;
                }
                if (uap->level == CPU_LEVEL_ROOT)
                        nset = cpuset_refroot(set);
                else
                        nset = cpuset_refbase(set);
                CPU_COPY(&nset->cs_mask, mask);
                cpuset_rel(nset);
                break;
        case CPU_LEVEL_WHICH:
                switch (uap->which) {
                case CPU_WHICH_TID:
                        thread_lock(ttd);
                        CPU_COPY(&ttd->td_cpuset->cs_mask, mask);
                        thread_unlock(ttd);
                        break;
                case CPU_WHICH_PID:
                        FOREACH_THREAD_IN_PROC(p, ttd) {
                                thread_lock(ttd);
                                CPU_OR(mask, &ttd->td_cpuset->cs_mask);
                                thread_unlock(ttd);
                        }
                        break;
                case CPU_WHICH_CPUSET:
                case CPU_WHICH_JAIL:
                        CPU_COPY(&set->cs_mask, mask);
                        break;
                case CPU_WHICH_IRQ:
                        error = intr_getaffinity(uap->id, mask);
                        break;
                }
                break;
        default:
                error = EINVAL;
                break;
        }
        if (set)
                cpuset_rel(set);
        if (p)
                PROC_UNLOCK(p);
        if (error == 0)
                error = copyout(mask, uap->mask, size);
out:
        free(mask, M_TEMP);
        return (error);
}

#ifndef _SYS_SYSPROTO_H_
struct cpuset_setaffinity_args {
        cpulevel_t      level;
        cpuwhich_t      which;
        id_t            id;
        size_t          cpusetsize;
        const cpuset_t  *mask;
};
#endif
int
sys_cpuset_setaffinity(struct thread *td, struct cpuset_setaffinity_args *uap)
{
        struct cpuset *nset;
        struct cpuset *set;
        struct thread *ttd;
        struct proc *p;
        cpuset_t *mask;
        int error;

        if (uap->cpusetsize < sizeof(cpuset_t) ||
            uap->cpusetsize > CPU_MAXSIZE / NBBY)
                return (ERANGE);
        mask = malloc(uap->cpusetsize, M_TEMP, M_WAITOK | M_ZERO);
        error = copyin(uap->mask, mask, uap->cpusetsize);
        if (error)
                goto out;
        /*
         * Verify that no high bits are set.
         */
        if (uap->cpusetsize > sizeof(cpuset_t)) {
                char *end;
                char *cp;

                end = cp = (char *)&mask->__bits;
                end += uap->cpusetsize;
                cp += sizeof(cpuset_t);
                while (cp != end)
                        if (*cp++ != 0) {
                                error = EINVAL;
                                goto out;
                        }

        }
        switch (uap->level) {
        case CPU_LEVEL_ROOT:
        case CPU_LEVEL_CPUSET:
                error = cpuset_which(uap->which, uap->id, &p, &ttd, &set);
                if (error)
                        break;
                switch (uap->which) {
                case CPU_WHICH_TID:
                case CPU_WHICH_PID:
                        thread_lock(ttd);
                        set = cpuset_ref(ttd->td_cpuset);
                        thread_unlock(ttd);
                        PROC_UNLOCK(p);
                        break;
                case CPU_WHICH_CPUSET:
                case CPU_WHICH_JAIL:
                        break;
                case CPU_WHICH_IRQ:
                        error = EINVAL;
                        goto out;
                }
                if (uap->level == CPU_LEVEL_ROOT)
                        nset = cpuset_refroot(set);
                else
                        nset = cpuset_refbase(set);
                error = cpuset_modify(nset, mask);
                cpuset_rel(nset);
                cpuset_rel(set);
                break;
        case CPU_LEVEL_WHICH:
                switch (uap->which) {
                case CPU_WHICH_TID:
                        error = cpuset_setthread(uap->id, mask);
                        break;
                case CPU_WHICH_PID:
                        error = cpuset_setproc(uap->id, NULL, mask);
                        break;
                case CPU_WHICH_CPUSET:
                case CPU_WHICH_JAIL:
                        error = cpuset_which(uap->which, uap->id, &p,
                            &ttd, &set);
                        if (error == 0) {
                                error = cpuset_modify(set, mask);
                                cpuset_rel(set);
                        }
                        break;
                case CPU_WHICH_IRQ:
                        error = intr_setaffinity(uap->id, mask);
                        break;
                default:
                        error = EINVAL;
                        break;
                }
                break;
        default:
                error = EINVAL;
                break;
        }
out:
        free(mask, M_TEMP);
        return (error);
}

#ifdef DDB
void
ddb_display_cpuset(const cpuset_t *set)
{
        int cpu, once;

        for (once = 0, cpu = 0; cpu < CPU_SETSIZE; cpu++) {
                if (CPU_ISSET(cpu, set)) {
                        if (once == 0) {
                                db_printf("%d", cpu);
                                once = 1;
                        } else  
                                db_printf(",%d", cpu);
                }
        }
        if (once == 0)
                db_printf("<none>");
}

DB_SHOW_COMMAND(cpusets, db_show_cpusets)
{
        struct cpuset *set;

        LIST_FOREACH(set, &cpuset_ids, cs_link) {
                db_printf("set=%p id=%-6u ref=%-6d flags=0x%04x parent id=%d\n",
                    set, set->cs_id, set->cs_ref, set->cs_flags,
                    (set->cs_parent != NULL) ? set->cs_parent->cs_id : 0);
                db_printf("  mask=");
                ddb_display_cpuset(&set->cs_mask);
                db_printf("\n");
                if (db_pager_quit)
                        break;
        }
}
#endif /* DDB */