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sysctl: switch sysctllock to a sleepable rmlock

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The lock is almost never taken for writing.
This commit is contained in:
Mateusz Guzik 2015-07-04 06:54:15 +00:00
parent 8cad626fbb
commit b8633775a8
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=285125
4 changed files with 110 additions and 100 deletions
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8
sys/kern/kern_linker.c
View File

@ -292,10 +292,10 @@ linker_file_register_sysctls(linker_file_t lf)
return;
sx_xunlock(&kld_sx);
sysctl_xlock();
sysctl_wlock();
for (oidp = start; oidp < stop; oidp++)
sysctl_register_oid(*oidp);
sysctl_xunlock();
sysctl_wunlock();
sx_xlock(&kld_sx);
}
@ -313,10 +313,10 @@ linker_file_unregister_sysctls(linker_file_t lf)
return;
sx_xunlock(&kld_sx);
sysctl_xlock();
sysctl_wlock();
for (oidp = start; oidp < stop; oidp++)
sysctl_unregister_oid(*oidp);
sysctl_xunlock();
sysctl_wunlock();
sx_xlock(&kld_sx);
}

194
sys/kern/kern_sysctl.c
View File

@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$");
#include <sys/jail.h>
#include <sys/lock.h>
#include <sys/mutex.h>
#include <sys/rmlock.h>
#include <sys/sbuf.h>
#include <sys/sx.h>
#include <sys/sysproto.h>
@ -77,7 +78,7 @@ static MALLOC_DEFINE(M_SYSCTLTMP, "sysctltmp", "sysctl temp output buffer");
* The sysctllock protects the MIB tree. It also protects sysctl
* contexts used with dynamic sysctls. The sysctl_register_oid() and
* sysctl_unregister_oid() routines require the sysctllock to already
* be held, so the sysctl_xlock() and sysctl_xunlock() routines are
* be held, so the sysctl_wlock() and sysctl_wunlock() routines are
* provided for the few places in the kernel which need to use that
* API rather than using the dynamic API. Use of the dynamic API is
* strongly encouraged for most code.
@ -86,20 +87,21 @@ static MALLOC_DEFINE(M_SYSCTLTMP, "sysctltmp", "sysctl temp output buffer");
* sysctl requests. This is implemented by serializing any userland
* sysctl requests larger than a single page via an exclusive lock.
*/
static struct sx sysctllock;
static struct rmlock sysctllock;
static struct sx sysctlmemlock;
#define SYSCTL_XLOCK() sx_xlock(&sysctllock)
#define SYSCTL_XUNLOCK() sx_xunlock(&sysctllock)
#define SYSCTL_SLOCK() sx_slock(&sysctllock)
#define SYSCTL_SUNLOCK() sx_sunlock(&sysctllock)
#define SYSCTL_XLOCKED() sx_xlocked(&sysctllock)
#define SYSCTL_ASSERT_LOCKED() sx_assert(&sysctllock, SA_LOCKED)
#define SYSCTL_ASSERT_XLOCKED() sx_assert(&sysctllock, SA_XLOCKED)
#define SYSCTL_ASSERT_SLOCKED() sx_assert(&sysctllock, SA_SLOCKED)
#define SYSCTL_INIT() sx_init(&sysctllock, "sysctl lock")
#define SYSCTL_WLOCK() do { printf("wlocked!\n"); rm_wlock(&sysctllock); } while (0)
#define SYSCTL_WUNLOCK() rm_wunlock(&sysctllock)
#define SYSCTL_RLOCK(tracker) rm_rlock(&sysctllock, (tracker))
#define SYSCTL_RUNLOCK(tracker) rm_runlock(&sysctllock, (tracker))
#define SYSCTL_WLOCKED() rm_wowned(&sysctllock)
#define SYSCTL_ASSERT_LOCKED() rm_assert(&sysctllock, RA_LOCKED)
#define SYSCTL_ASSERT_WLOCKED() rm_assert(&sysctllock, RA_WLOCKED)
#define SYSCTL_ASSERT_RLOCKED() rm_assert(&sysctllock, RA_RLOCKED)
#define SYSCTL_INIT() rm_init_flags(&sysctllock, "sysctl lock", \
RM_SLEEPABLE)
#define SYSCTL_SLEEP(ch, wmesg, timo) \
sx_sleep(ch, &sysctllock, 0, wmesg, timo)
rm_sleep(ch, &sysctllock, 0, wmesg, timo)
static int sysctl_root(SYSCTL_HANDLER_ARGS);
@ -112,26 +114,23 @@ static int sysctl_old_kernel(struct sysctl_req *, const void *, size_t);
static int sysctl_new_kernel(struct sysctl_req *, void *, size_t);
static void
sysctl_lock(bool xlock)
sysctl_lock(struct rm_priotracker *tracker)
{
if (xlock)
SYSCTL_XLOCK();
if (tracker != NULL)
SYSCTL_RLOCK(tracker);
else
SYSCTL_SLOCK();
SYSCTL_WLOCK();
}
static bool
sysctl_unlock(void)
static void
sysctl_unlock(struct rm_priotracker *tracker)
{
bool xlocked;
xlocked = SYSCTL_XLOCKED();
if (xlocked)
SYSCTL_XUNLOCK();
if (tracker != NULL)
SYSCTL_RUNLOCK(tracker);
else
SYSCTL_SUNLOCK();
return (xlocked);
SYSCTL_WUNLOCK();
}
static struct sysctl_oid *
@ -154,29 +153,28 @@ sysctl_find_oidname(const char *name, struct sysctl_oid_list *list)
* Order by number in each list.
*/
void
sysctl_xlock(void)
sysctl_wlock(void)
{
SYSCTL_XLOCK();
SYSCTL_WLOCK();
}
void
sysctl_xunlock(void)
sysctl_wunlock(void)
{
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
}
static int
sysctl_root_handler_locked(struct sysctl_oid *oid, void *arg1, intptr_t arg2,
struct sysctl_req *req)
struct sysctl_req *req, struct rm_priotracker *tracker)
{
int error;
bool xlocked;
if (oid->oid_kind & CTLFLAG_DYN)
atomic_add_int(&oid->oid_running, 1);
xlocked = sysctl_unlock();
sysctl_unlock(tracker);
if (!(oid->oid_kind & CTLFLAG_MPSAFE))
mtx_lock(&Giant);
@ -184,7 +182,7 @@ sysctl_root_handler_locked(struct sysctl_oid *oid, void *arg1, intptr_t arg2,
if (!(oid->oid_kind & CTLFLAG_MPSAFE))
mtx_unlock(&Giant);
sysctl_lock(xlocked);
sysctl_lock(tracker);
if (oid->oid_kind & CTLFLAG_DYN) {
if (atomic_fetchadd_int(&oid->oid_running, -1) == 1 &&
(oid->oid_kind & CTLFLAG_DYING) != 0)
@ -283,7 +281,7 @@ sysctl_load_tunable_by_oid_locked(struct sysctl_oid *oidp)
return;
}
error = sysctl_root_handler_locked(oidp, oidp->oid_arg1,
oidp->oid_arg2, &req);
oidp->oid_arg2, &req, NULL);
if (error != 0)
printf("Setting sysctl %s failed: %d\n", path + rem, error);
if (penv != NULL)
@ -303,7 +301,7 @@ sysctl_register_oid(struct sysctl_oid *oidp)
* First check if another oid with the same name already
* exists in the parent's list.
*/
SYSCTL_ASSERT_XLOCKED();
SYSCTL_ASSERT_WLOCKED();
p = sysctl_find_oidname(oidp->oid_name, parent);
if (p != NULL) {
if ((p->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
@ -397,7 +395,7 @@ sysctl_unregister_oid(struct sysctl_oid *oidp)
struct sysctl_oid *p;
int error;
SYSCTL_ASSERT_XLOCKED();
SYSCTL_ASSERT_WLOCKED();
error = ENOENT;
if (oidp->oid_number == OID_AUTO) {
error = EINVAL;
@ -453,7 +451,7 @@ sysctl_ctx_free(struct sysctl_ctx_list *clist)
* XXX This algorithm is a hack. But I don't know any
* XXX better solution for now...
*/
SYSCTL_XLOCK();
SYSCTL_WLOCK();
TAILQ_FOREACH(e, clist, link) {
error = sysctl_remove_oid_locked(e->entry, 0, 0);
if (error)
@ -473,7 +471,7 @@ sysctl_ctx_free(struct sysctl_ctx_list *clist)
e1 = TAILQ_PREV(e1, sysctl_ctx_list, link);
}
if (error) {
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return(EBUSY);
}
/* Now really delete the entries */
@ -487,7 +485,7 @@ sysctl_ctx_free(struct sysctl_ctx_list *clist)
free(e, M_SYSCTLOID);
e = e1;
}
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (error);
}
@ -497,7 +495,7 @@ sysctl_ctx_entry_add(struct sysctl_ctx_list *clist, struct sysctl_oid *oidp)
{
struct sysctl_ctx_entry *e;
SYSCTL_ASSERT_XLOCKED();
SYSCTL_ASSERT_WLOCKED();
if (clist == NULL || oidp == NULL)
return(NULL);
e = malloc(sizeof(struct sysctl_ctx_entry), M_SYSCTLOID, M_WAITOK);
@ -512,7 +510,7 @@ sysctl_ctx_entry_find(struct sysctl_ctx_list *clist, struct sysctl_oid *oidp)
{
struct sysctl_ctx_entry *e;
SYSCTL_ASSERT_XLOCKED();
SYSCTL_ASSERT_WLOCKED();
if (clist == NULL || oidp == NULL)
return(NULL);
TAILQ_FOREACH(e, clist, link) {
@ -534,15 +532,15 @@ sysctl_ctx_entry_del(struct sysctl_ctx_list *clist, struct sysctl_oid *oidp)
if (clist == NULL || oidp == NULL)
return (EINVAL);
SYSCTL_XLOCK();
SYSCTL_WLOCK();
e = sysctl_ctx_entry_find(clist, oidp);
if (e != NULL) {
TAILQ_REMOVE(clist, e, link);
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
free(e, M_SYSCTLOID);
return (0);
} else {
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (ENOENT);
}
}
@ -558,9 +556,9 @@ sysctl_remove_oid(struct sysctl_oid *oidp, int del, int recurse)
{
int error;
SYSCTL_XLOCK();
SYSCTL_WLOCK();
error = sysctl_remove_oid_locked(oidp, del, recurse);
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (error);
}
@ -572,14 +570,14 @@ sysctl_remove_name(struct sysctl_oid *parent, const char *name,
int error;
error = ENOENT;
SYSCTL_XLOCK();
SYSCTL_WLOCK();
SLIST_FOREACH_SAFE(p, SYSCTL_CHILDREN(parent), oid_link, tmp) {
if (strcmp(p->oid_name, name) == 0) {
error = sysctl_remove_oid_locked(p, del, recurse);
break;
}
}
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (error);
}
@ -591,7 +589,7 @@ sysctl_remove_oid_locked(struct sysctl_oid *oidp, int del, int recurse)
struct sysctl_oid *p, *tmp;
int error;
SYSCTL_ASSERT_XLOCKED();
SYSCTL_ASSERT_WLOCKED();
if (oidp == NULL)
return(EINVAL);
if ((oidp->oid_kind & CTLFLAG_DYN) == 0) {
@ -666,7 +664,7 @@ sysctl_add_oid(struct sysctl_ctx_list *clist, struct sysctl_oid_list *parent,
if (parent == NULL)
return(NULL);
/* Check if the node already exists, otherwise create it */
SYSCTL_XLOCK();
SYSCTL_WLOCK();
oidp = sysctl_find_oidname(name, parent);
if (oidp != NULL) {
if ((oidp->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
@ -674,10 +672,10 @@ sysctl_add_oid(struct sysctl_ctx_list *clist, struct sysctl_oid_list *parent,
/* Update the context */
if (clist != NULL)
sysctl_ctx_entry_add(clist, oidp);
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (oidp);
} else {
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
printf("can't re-use a leaf (%s)!\n", name);
return (NULL);
}
@ -700,7 +698,7 @@ sysctl_add_oid(struct sysctl_ctx_list *clist, struct sysctl_oid_list *parent,
sysctl_ctx_entry_add(clist, oidp);
/* Register this oid */
sysctl_register_oid(oidp);
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (oidp);
}
@ -714,10 +712,10 @@ sysctl_rename_oid(struct sysctl_oid *oidp, const char *name)
char *oldname;
newname = strdup(name, M_SYSCTLOID);
SYSCTL_XLOCK();
SYSCTL_WLOCK();
oldname = __DECONST(char *, oidp->oid_name);
oidp->oid_name = newname;
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
free(oldname, M_SYSCTLOID);
}
@ -729,21 +727,21 @@ sysctl_move_oid(struct sysctl_oid *oid, struct sysctl_oid_list *parent)
{
struct sysctl_oid *oidp;
SYSCTL_XLOCK();
SYSCTL_WLOCK();
if (oid->oid_parent == parent) {
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (0);
}
oidp = sysctl_find_oidname(oid->oid_name, parent);
if (oidp != NULL) {
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (EEXIST);
}
sysctl_unregister_oid(oid);
oid->oid_parent = parent;
oid->oid_number = OID_AUTO;
sysctl_register_oid(oid);
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
return (0);
}
@ -759,10 +757,10 @@ sysctl_register_all(void *arg)
sx_init(&sysctlmemlock, "sysctl mem");
SYSCTL_INIT();
SYSCTL_XLOCK();
SYSCTL_WLOCK();
SET_FOREACH(oidp, sysctl_set)
sysctl_register_oid(*oidp);
SYSCTL_XUNLOCK();
SYSCTL_WUNLOCK();
}
SYSINIT(sysctl, SI_SUB_KMEM, SI_ORDER_FIRST, sysctl_register_all, 0);
@ -832,14 +830,15 @@ sysctl_sysctl_debug_dump_node(struct sysctl_oid_list *l, int i)
static int
sysctl_sysctl_debug(SYSCTL_HANDLER_ARGS)
{
struct rm_priotracker tracker;
int error;
error = priv_check(req->td, PRIV_SYSCTL_DEBUG);
if (error)
return (error);
SYSCTL_SLOCK();
SYSCTL_RLOCK(&tracker);
sysctl_sysctl_debug_dump_node(&sysctl__children, 0);
SYSCTL_SUNLOCK();
SYSCTL_RUNLOCK(&tracker);
return (ENOENT);
}
@ -855,9 +854,10 @@ sysctl_sysctl_name(SYSCTL_HANDLER_ARGS)
int error = 0;
struct sysctl_oid *oid;
struct sysctl_oid_list *lsp = &sysctl__children, *lsp2;
struct rm_priotracker tracker;
char buf[10];
SYSCTL_SLOCK();
SYSCTL_RLOCK(&tracker);
while (namelen) {
if (!lsp) {
snprintf(buf,sizeof(buf),"%d",*name);
@ -900,7 +900,7 @@ sysctl_sysctl_name(SYSCTL_HANDLER_ARGS)
}
error = SYSCTL_OUT(req, "", 1);
out:
SYSCTL_SUNLOCK();
SYSCTL_RUNLOCK(&tracker);
return (error);
}
@ -979,11 +979,12 @@ sysctl_sysctl_next(SYSCTL_HANDLER_ARGS)
int i, j, error;
struct sysctl_oid *oid;
struct sysctl_oid_list *lsp = &sysctl__children;
struct rm_priotracker tracker;
int newoid[CTL_MAXNAME];
SYSCTL_SLOCK();
SYSCTL_RLOCK(&tracker);
i = sysctl_sysctl_next_ls(lsp, name, namelen, newoid, &j, 1, &oid);
SYSCTL_SUNLOCK();
SYSCTL_RUNLOCK(&tracker);
if (i)
return (ENOENT);
error = SYSCTL_OUT(req, newoid, j * sizeof (int));
@ -1042,6 +1043,7 @@ sysctl_sysctl_name2oid(SYSCTL_HANDLER_ARGS)
char *p;
int error, oid[CTL_MAXNAME], len = 0;
struct sysctl_oid *op = 0;
struct rm_priotracker tracker;
if (!req->newlen)
return (ENOENT);
@ -1058,9 +1060,9 @@ sysctl_sysctl_name2oid(SYSCTL_HANDLER_ARGS)
p [req->newlen] = '\0';
SYSCTL_SLOCK();
SYSCTL_RLOCK(&tracker);
error = name2oid(p, oid, &len, &op);
SYSCTL_SUNLOCK();
SYSCTL_RUNLOCK(&tracker);
free(p, M_SYSCTL);
@ -1083,9 +1085,10 @@ static int
sysctl_sysctl_oidfmt(SYSCTL_HANDLER_ARGS)
{
struct sysctl_oid *oid;
struct rm_priotracker tracker;
int error;
SYSCTL_SLOCK();
SYSCTL_RLOCK(&tracker);
error = sysctl_find_oid(arg1, arg2, &oid, NULL, req);
if (error)
goto out;
@ -1099,7 +1102,7 @@ sysctl_sysctl_oidfmt(SYSCTL_HANDLER_ARGS)
goto out;
error = SYSCTL_OUT(req, oid->oid_fmt, strlen(oid->oid_fmt) + 1);
out:
SYSCTL_SUNLOCK();
SYSCTL_RUNLOCK(&tracker);
return (error);
}
@ -1111,9 +1114,10 @@ static int
sysctl_sysctl_oiddescr(SYSCTL_HANDLER_ARGS)
{
struct sysctl_oid *oid;
struct rm_priotracker tracker;
int error;
SYSCTL_SLOCK();
SYSCTL_RLOCK(&tracker);
error = sysctl_find_oid(arg1, arg2, &oid, NULL, req);
if (error)
goto out;
@ -1124,7 +1128,7 @@ sysctl_sysctl_oiddescr(SYSCTL_HANDLER_ARGS)
}
error = SYSCTL_OUT(req, oid->oid_descr, strlen(oid->oid_descr) + 1);
out:
SYSCTL_SUNLOCK();
SYSCTL_RUNLOCK(&tracker);
return (error);
}
@ -1429,9 +1433,7 @@ kernel_sysctl(struct thread *td, int *name, u_int namelen, void *old,
req.newfunc = sysctl_new_kernel;
req.lock = REQ_UNWIRED;
SYSCTL_SLOCK();
error = sysctl_root(0, name, namelen, &req);
SYSCTL_SUNLOCK();
if (req.lock == REQ_WIRED && req.validlen > 0)
vsunlock(req.oldptr, req.validlen);
@ -1608,13 +1610,14 @@ static int
sysctl_root(SYSCTL_HANDLER_ARGS)
{
struct sysctl_oid *oid;
struct rm_priotracker tracker;
int error, indx, lvl;
SYSCTL_ASSERT_SLOCKED();
SYSCTL_RLOCK(&tracker);
error = sysctl_find_oid(arg1, arg2, &oid, &indx, req);
if (error)
return (error);
goto out;
if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
/*
@ -1622,13 +1625,17 @@ sysctl_root(SYSCTL_HANDLER_ARGS)
* no handler. Inform the user that it's a node.
* The indx may or may not be the same as namelen.
*/
if (oid->oid_handler == NULL)
return (EISDIR);
if (oid->oid_handler == NULL) {
error = EISDIR;
goto out;
}
}
/* Is this sysctl writable? */
if (req->newptr && !(oid->oid_kind & CTLFLAG_WR))
return (EPERM);
if (req->newptr && !(oid->oid_kind & CTLFLAG_WR)) {
error = EPERM;
goto out;
}
KASSERT(req->td != NULL, ("sysctl_root(): req->td == NULL"));
@ -1638,10 +1645,11 @@ sysctl_root(SYSCTL_HANDLER_ARGS)
* writing unless specifically granted for the node.
*/
if (IN_CAPABILITY_MODE(req->td)) {
if (req->oldptr && !(oid->oid_kind & CTLFLAG_CAPRD))
return (EPERM);
if (req->newptr && !(oid->oid_kind & CTLFLAG_CAPWR))
return (EPERM);
if ((req->oldptr && !(oid->oid_kind & CTLFLAG_CAPRD)) ||
(req->newptr && !(oid->oid_kind & CTLFLAG_CAPWR))) {
error = EPERM;
goto out;
}
}
#endif
@ -1650,7 +1658,7 @@ sysctl_root(SYSCTL_HANDLER_ARGS)
lvl = (oid->oid_kind & CTLMASK_SECURE) >> CTLSHIFT_SECURE;
error = securelevel_gt(req->td->td_ucred, lvl);
if (error)
return (error);
goto out;
}
/* Is this sysctl writable by only privileged users? */
@ -1668,11 +1676,13 @@ sysctl_root(SYSCTL_HANDLER_ARGS)
priv = PRIV_SYSCTL_WRITE;
error = priv_check(req->td, priv);
if (error)
return (error);
goto out;
}
if (!oid->oid_handler)
return (EINVAL);
if (!oid->oid_handler) {
error = EINVAL;
goto out;
}
if ((oid->oid_kind & CTLTYPE) == CTLTYPE_NODE) {
arg1 = (int *)arg1 + indx;
@ -1685,16 +1695,18 @@ sysctl_root(SYSCTL_HANDLER_ARGS)
error = mac_system_check_sysctl(req->td->td_ucred, oid, arg1, arg2,
req);
if (error != 0)
return (error);
goto out;
#endif
#ifdef VIMAGE
if ((oid->oid_kind & CTLFLAG_VNET) && arg1 != NULL)
arg1 = (void *)(curvnet->vnet_data_base + (uintptr_t)arg1);
#endif
error = sysctl_root_handler_locked(oid, arg1, arg2, req);
error = sysctl_root_handler_locked(oid, arg1, arg2, req, &tracker);
KFAIL_POINT_ERROR(_debug_fail_point, sysctl_running, error);
out:
SYSCTL_RUNLOCK(&tracker);
return (error);
}
@ -1794,9 +1806,7 @@ userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
for (;;) {
req.oldidx = 0;
req.newidx = 0;
SYSCTL_SLOCK();
error = sysctl_root(0, name, namelen, &req);
SYSCTL_SUNLOCK();
if (error != EAGAIN)
break;
kern_yield(PRI_USER);

4
sys/kern/vfs_init.c
View File

@ -291,7 +291,7 @@ vfs_register(struct vfsconf *vfc)
* preserved by re-registering the oid after modifying its
* number.
*/
sysctl_xlock();
sysctl_wlock();
SLIST_FOREACH(oidp, SYSCTL_CHILDREN(&sysctl___vfs), oid_link) {
if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
sysctl_unregister_oid(oidp);
@ -300,7 +300,7 @@ vfs_register(struct vfsconf *vfc)
break;
}
}
sysctl_xunlock();
sysctl_wunlock();
return (0);
}

4
sys/sys/sysctl.h
View File

@ -807,8 +807,8 @@ int userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
size_t *retval, int flags);
int sysctl_find_oid(int *name, u_int namelen, struct sysctl_oid **noid,
int *nindx, struct sysctl_req *req);
void sysctl_xlock(void);
void sysctl_xunlock(void);
void sysctl_wlock(void);
void sysctl_wunlock(void);
int sysctl_wire_old_buffer(struct sysctl_req *req, size_t len);
struct sbuf;