freebsd-dev/sys/kern/kern_mbuf.c
Navdeep Parhar a9fa76f27e Test for absence of M_NOFREE before attempting to purge the mbuf's tags.
This will leave more state intact should the assertion go off.

MFC after:	1 month
2014-09-30 23:16:26 +00:00

681 lines
19 KiB
C

/*-
* Copyright (c) 2004, 2005,
* Bosko Milekic <bmilekic@FreeBSD.org>. 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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("$FreeBSD$");
#include "opt_param.h"
#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/eventhandler.h>
#include <sys/kernel.h>
#include <sys/protosw.h>
#include <sys/smp.h>
#include <sys/sysctl.h>
#include <security/mac/mac_framework.h>
#include <vm/vm.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/uma.h>
#include <vm/uma_int.h>
#include <vm/uma_dbg.h>
/*
* In FreeBSD, Mbufs and Mbuf Clusters are allocated from UMA
* Zones.
*
* Mbuf Clusters (2K, contiguous) are allocated from the Cluster
* Zone. The Zone can be capped at kern.ipc.nmbclusters, if the
* administrator so desires.
*
* Mbufs are allocated from a UMA Master Zone called the Mbuf
* Zone.
*
* Additionally, FreeBSD provides a Packet Zone, which it
* configures as a Secondary Zone to the Mbuf Master Zone,
* thus sharing backend Slab kegs with the Mbuf Master Zone.
*
* Thus common-case allocations and locking are simplified:
*
* m_clget() m_getcl()
* | |
* | .------------>[(Packet Cache)] m_get(), m_gethdr()
* | | [ Packet ] |
* [(Cluster Cache)] [ Secondary ] [ (Mbuf Cache) ]
* [ Cluster Zone ] [ Zone ] [ Mbuf Master Zone ]
* | \________ |
* [ Cluster Keg ] \ /
* | [ Mbuf Keg ]
* [ Cluster Slabs ] |
* | [ Mbuf Slabs ]
* \____________(VM)_________________/
*
*
* Whenever an object is allocated with uma_zalloc() out of
* one of the Zones its _ctor_ function is executed. The same
* for any deallocation through uma_zfree() the _dtor_ function
* is executed.
*
* Caches are per-CPU and are filled from the Master Zone.
*
* Whenever an object is allocated from the underlying global
* memory pool it gets pre-initialized with the _zinit_ functions.
* When the Keg's are overfull objects get decomissioned with
* _zfini_ functions and free'd back to the global memory pool.
*
*/
int nmbufs; /* limits number of mbufs */
int nmbclusters; /* limits number of mbuf clusters */
int nmbjumbop; /* limits number of page size jumbo clusters */
int nmbjumbo9; /* limits number of 9k jumbo clusters */
int nmbjumbo16; /* limits number of 16k jumbo clusters */
static quad_t maxmbufmem; /* overall real memory limit for all mbufs */
SYSCTL_QUAD(_kern_ipc, OID_AUTO, maxmbufmem, CTLFLAG_RDTUN | CTLFLAG_NOFETCH, &maxmbufmem, 0,
"Maximum real memory allocatable to various mbuf types");
/*
* tunable_mbinit() has to be run before any mbuf allocations are done.
*/
static void
tunable_mbinit(void *dummy)
{
quad_t realmem;
/*
* The default limit for all mbuf related memory is 1/2 of all
* available kernel memory (physical or kmem).
* At most it can be 3/4 of available kernel memory.
*/
realmem = qmin((quad_t)physmem * PAGE_SIZE, vm_kmem_size);
maxmbufmem = realmem / 2;
TUNABLE_QUAD_FETCH("kern.ipc.maxmbufmem", &maxmbufmem);
if (maxmbufmem > realmem / 4 * 3)
maxmbufmem = realmem / 4 * 3;
TUNABLE_INT_FETCH("kern.ipc.nmbclusters", &nmbclusters);
if (nmbclusters == 0)
nmbclusters = maxmbufmem / MCLBYTES / 4;
TUNABLE_INT_FETCH("kern.ipc.nmbjumbop", &nmbjumbop);
if (nmbjumbop == 0)
nmbjumbop = maxmbufmem / MJUMPAGESIZE / 4;
TUNABLE_INT_FETCH("kern.ipc.nmbjumbo9", &nmbjumbo9);
if (nmbjumbo9 == 0)
nmbjumbo9 = maxmbufmem / MJUM9BYTES / 6;
TUNABLE_INT_FETCH("kern.ipc.nmbjumbo16", &nmbjumbo16);
if (nmbjumbo16 == 0)
nmbjumbo16 = maxmbufmem / MJUM16BYTES / 6;
/*
* We need at least as many mbufs as we have clusters of
* the various types added together.
*/
TUNABLE_INT_FETCH("kern.ipc.nmbufs", &nmbufs);
if (nmbufs < nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16)
nmbufs = lmax(maxmbufmem / MSIZE / 5,
nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16);
}
SYSINIT(tunable_mbinit, SI_SUB_KMEM, SI_ORDER_MIDDLE, tunable_mbinit, NULL);
static int
sysctl_nmbclusters(SYSCTL_HANDLER_ARGS)
{
int error, newnmbclusters;
newnmbclusters = nmbclusters;
error = sysctl_handle_int(oidp, &newnmbclusters, 0, req);
if (error == 0 && req->newptr && newnmbclusters != nmbclusters) {
if (newnmbclusters > nmbclusters &&
nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
nmbclusters = newnmbclusters;
nmbclusters = uma_zone_set_max(zone_clust, nmbclusters);
EVENTHANDLER_INVOKE(nmbclusters_change);
} else
error = EINVAL;
}
return (error);
}
SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbclusters, CTLTYPE_INT|CTLFLAG_RW,
&nmbclusters, 0, sysctl_nmbclusters, "IU",
"Maximum number of mbuf clusters allowed");
static int
sysctl_nmbjumbop(SYSCTL_HANDLER_ARGS)
{
int error, newnmbjumbop;
newnmbjumbop = nmbjumbop;
error = sysctl_handle_int(oidp, &newnmbjumbop, 0, req);
if (error == 0 && req->newptr && newnmbjumbop != nmbjumbop) {
if (newnmbjumbop > nmbjumbop &&
nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
nmbjumbop = newnmbjumbop;
nmbjumbop = uma_zone_set_max(zone_jumbop, nmbjumbop);
} else
error = EINVAL;
}
return (error);
}
SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbjumbop, CTLTYPE_INT|CTLFLAG_RW,
&nmbjumbop, 0, sysctl_nmbjumbop, "IU",
"Maximum number of mbuf page size jumbo clusters allowed");
static int
sysctl_nmbjumbo9(SYSCTL_HANDLER_ARGS)
{
int error, newnmbjumbo9;
newnmbjumbo9 = nmbjumbo9;
error = sysctl_handle_int(oidp, &newnmbjumbo9, 0, req);
if (error == 0 && req->newptr && newnmbjumbo9 != nmbjumbo9) {
if (newnmbjumbo9 > nmbjumbo9 &&
nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
nmbjumbo9 = newnmbjumbo9;
nmbjumbo9 = uma_zone_set_max(zone_jumbo9, nmbjumbo9);
} else
error = EINVAL;
}
return (error);
}
SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbjumbo9, CTLTYPE_INT|CTLFLAG_RW,
&nmbjumbo9, 0, sysctl_nmbjumbo9, "IU",
"Maximum number of mbuf 9k jumbo clusters allowed");
static int
sysctl_nmbjumbo16(SYSCTL_HANDLER_ARGS)
{
int error, newnmbjumbo16;
newnmbjumbo16 = nmbjumbo16;
error = sysctl_handle_int(oidp, &newnmbjumbo16, 0, req);
if (error == 0 && req->newptr && newnmbjumbo16 != nmbjumbo16) {
if (newnmbjumbo16 > nmbjumbo16 &&
nmbufs >= nmbclusters + nmbjumbop + nmbjumbo9 + nmbjumbo16) {
nmbjumbo16 = newnmbjumbo16;
nmbjumbo16 = uma_zone_set_max(zone_jumbo16, nmbjumbo16);
} else
error = EINVAL;
}
return (error);
}
SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbjumbo16, CTLTYPE_INT|CTLFLAG_RW,
&nmbjumbo16, 0, sysctl_nmbjumbo16, "IU",
"Maximum number of mbuf 16k jumbo clusters allowed");
static int
sysctl_nmbufs(SYSCTL_HANDLER_ARGS)
{
int error, newnmbufs;
newnmbufs = nmbufs;
error = sysctl_handle_int(oidp, &newnmbufs, 0, req);
if (error == 0 && req->newptr && newnmbufs != nmbufs) {
if (newnmbufs > nmbufs) {
nmbufs = newnmbufs;
nmbufs = uma_zone_set_max(zone_mbuf, nmbufs);
EVENTHANDLER_INVOKE(nmbufs_change);
} else
error = EINVAL;
}
return (error);
}
SYSCTL_PROC(_kern_ipc, OID_AUTO, nmbufs, CTLTYPE_INT|CTLFLAG_RW,
&nmbufs, 0, sysctl_nmbufs, "IU",
"Maximum number of mbufs allowed");
/*
* Zones from which we allocate.
*/
uma_zone_t zone_mbuf;
uma_zone_t zone_clust;
uma_zone_t zone_pack;
uma_zone_t zone_jumbop;
uma_zone_t zone_jumbo9;
uma_zone_t zone_jumbo16;
uma_zone_t zone_ext_refcnt;
/*
* Local prototypes.
*/
static int mb_ctor_mbuf(void *, int, void *, int);
static int mb_ctor_clust(void *, int, void *, int);
static int mb_ctor_pack(void *, int, void *, int);
static void mb_dtor_mbuf(void *, int, void *);
static void mb_dtor_clust(void *, int, void *);
static void mb_dtor_pack(void *, int, void *);
static int mb_zinit_pack(void *, int, int);
static void mb_zfini_pack(void *, int);
static void mb_reclaim(void *);
static void *mbuf_jumbo_alloc(uma_zone_t, int, uint8_t *, int);
/* Ensure that MSIZE is a power of 2. */
CTASSERT((((MSIZE - 1) ^ MSIZE) + 1) >> 1 == MSIZE);
/*
* Initialize FreeBSD Network buffer allocation.
*/
static void
mbuf_init(void *dummy)
{
/*
* Configure UMA zones for Mbufs, Clusters, and Packets.
*/
zone_mbuf = uma_zcreate(MBUF_MEM_NAME, MSIZE,
mb_ctor_mbuf, mb_dtor_mbuf,
#ifdef INVARIANTS
trash_init, trash_fini,
#else
NULL, NULL,
#endif
MSIZE - 1, UMA_ZONE_MAXBUCKET);
if (nmbufs > 0)
nmbufs = uma_zone_set_max(zone_mbuf, nmbufs);
uma_zone_set_warning(zone_mbuf, "kern.ipc.nmbufs limit reached");
zone_clust = uma_zcreate(MBUF_CLUSTER_MEM_NAME, MCLBYTES,
mb_ctor_clust, mb_dtor_clust,
#ifdef INVARIANTS
trash_init, trash_fini,
#else
NULL, NULL,
#endif
UMA_ALIGN_PTR, UMA_ZONE_REFCNT);
if (nmbclusters > 0)
nmbclusters = uma_zone_set_max(zone_clust, nmbclusters);
uma_zone_set_warning(zone_clust, "kern.ipc.nmbclusters limit reached");
zone_pack = uma_zsecond_create(MBUF_PACKET_MEM_NAME, mb_ctor_pack,
mb_dtor_pack, mb_zinit_pack, mb_zfini_pack, zone_mbuf);
/* Make jumbo frame zone too. Page size, 9k and 16k. */
zone_jumbop = uma_zcreate(MBUF_JUMBOP_MEM_NAME, MJUMPAGESIZE,
mb_ctor_clust, mb_dtor_clust,
#ifdef INVARIANTS
trash_init, trash_fini,
#else
NULL, NULL,
#endif
UMA_ALIGN_PTR, UMA_ZONE_REFCNT);
if (nmbjumbop > 0)
nmbjumbop = uma_zone_set_max(zone_jumbop, nmbjumbop);
uma_zone_set_warning(zone_jumbop, "kern.ipc.nmbjumbop limit reached");
zone_jumbo9 = uma_zcreate(MBUF_JUMBO9_MEM_NAME, MJUM9BYTES,
mb_ctor_clust, mb_dtor_clust,
#ifdef INVARIANTS
trash_init, trash_fini,
#else
NULL, NULL,
#endif
UMA_ALIGN_PTR, UMA_ZONE_REFCNT);
uma_zone_set_allocf(zone_jumbo9, mbuf_jumbo_alloc);
if (nmbjumbo9 > 0)
nmbjumbo9 = uma_zone_set_max(zone_jumbo9, nmbjumbo9);
uma_zone_set_warning(zone_jumbo9, "kern.ipc.nmbjumbo9 limit reached");
zone_jumbo16 = uma_zcreate(MBUF_JUMBO16_MEM_NAME, MJUM16BYTES,
mb_ctor_clust, mb_dtor_clust,
#ifdef INVARIANTS
trash_init, trash_fini,
#else
NULL, NULL,
#endif
UMA_ALIGN_PTR, UMA_ZONE_REFCNT);
uma_zone_set_allocf(zone_jumbo16, mbuf_jumbo_alloc);
if (nmbjumbo16 > 0)
nmbjumbo16 = uma_zone_set_max(zone_jumbo16, nmbjumbo16);
uma_zone_set_warning(zone_jumbo16, "kern.ipc.nmbjumbo16 limit reached");
zone_ext_refcnt = uma_zcreate(MBUF_EXTREFCNT_MEM_NAME, sizeof(u_int),
NULL, NULL,
NULL, NULL,
UMA_ALIGN_PTR, UMA_ZONE_ZINIT);
/* uma_prealloc() goes here... */
/*
* Hook event handler for low-memory situation, used to
* drain protocols and push data back to the caches (UMA
* later pushes it back to VM).
*/
EVENTHANDLER_REGISTER(vm_lowmem, mb_reclaim, NULL,
EVENTHANDLER_PRI_FIRST);
}
SYSINIT(mbuf, SI_SUB_MBUF, SI_ORDER_FIRST, mbuf_init, NULL);
/*
* UMA backend page allocator for the jumbo frame zones.
*
* Allocates kernel virtual memory that is backed by contiguous physical
* pages.
*/
static void *
mbuf_jumbo_alloc(uma_zone_t zone, int bytes, uint8_t *flags, int wait)
{
/* Inform UMA that this allocator uses kernel_map/object. */
*flags = UMA_SLAB_KERNEL;
return ((void *)kmem_alloc_contig(kernel_arena, bytes, wait,
(vm_paddr_t)0, ~(vm_paddr_t)0, 1, 0, VM_MEMATTR_DEFAULT));
}
/*
* Constructor for Mbuf master zone.
*
* The 'arg' pointer points to a mb_args structure which
* contains call-specific information required to support the
* mbuf allocation API. See mbuf.h.
*/
static int
mb_ctor_mbuf(void *mem, int size, void *arg, int how)
{
struct mbuf *m;
struct mb_args *args;
int error;
int flags;
short type;
#ifdef INVARIANTS
trash_ctor(mem, size, arg, how);
#endif
args = (struct mb_args *)arg;
type = args->type;
/*
* The mbuf is initialized later. The caller has the
* responsibility to set up any MAC labels too.
*/
if (type == MT_NOINIT)
return (0);
m = (struct mbuf *)mem;
flags = args->flags;
error = m_init(m, NULL, size, how, type, flags);
return (error);
}
/*
* The Mbuf master zone destructor.
*/
static void
mb_dtor_mbuf(void *mem, int size, void *arg)
{
struct mbuf *m;
unsigned long flags;
m = (struct mbuf *)mem;
flags = (unsigned long)arg;
KASSERT((m->m_flags & M_NOFREE) == 0, ("%s: M_NOFREE set", __func__));
if ((m->m_flags & M_PKTHDR) && !SLIST_EMPTY(&m->m_pkthdr.tags))
m_tag_delete_chain(m, NULL);
#ifdef INVARIANTS
trash_dtor(mem, size, arg);
#endif
}
/*
* The Mbuf Packet zone destructor.
*/
static void
mb_dtor_pack(void *mem, int size, void *arg)
{
struct mbuf *m;
m = (struct mbuf *)mem;
if ((m->m_flags & M_PKTHDR) != 0)
m_tag_delete_chain(m, NULL);
/* Make sure we've got a clean cluster back. */
KASSERT((m->m_flags & M_EXT) == M_EXT, ("%s: M_EXT not set", __func__));
KASSERT(m->m_ext.ext_buf != NULL, ("%s: ext_buf == NULL", __func__));
KASSERT(m->m_ext.ext_free == NULL, ("%s: ext_free != NULL", __func__));
KASSERT(m->m_ext.ext_arg1 == NULL, ("%s: ext_arg1 != NULL", __func__));
KASSERT(m->m_ext.ext_arg2 == NULL, ("%s: ext_arg2 != NULL", __func__));
KASSERT(m->m_ext.ext_size == MCLBYTES, ("%s: ext_size != MCLBYTES", __func__));
KASSERT(m->m_ext.ext_type == EXT_PACKET, ("%s: ext_type != EXT_PACKET", __func__));
KASSERT(*m->m_ext.ext_cnt == 1, ("%s: ext_cnt != 1", __func__));
#ifdef INVARIANTS
trash_dtor(m->m_ext.ext_buf, MCLBYTES, arg);
#endif
/*
* If there are processes blocked on zone_clust, waiting for pages
* to be freed up, * cause them to be woken up by draining the
* packet zone. We are exposed to a race here * (in the check for
* the UMA_ZFLAG_FULL) where we might miss the flag set, but that
* is deliberate. We don't want to acquire the zone lock for every
* mbuf free.
*/
if (uma_zone_exhausted_nolock(zone_clust))
zone_drain(zone_pack);
}
/*
* The Cluster and Jumbo[PAGESIZE|9|16] zone constructor.
*
* Here the 'arg' pointer points to the Mbuf which we
* are configuring cluster storage for. If 'arg' is
* empty we allocate just the cluster without setting
* the mbuf to it. See mbuf.h.
*/
static int
mb_ctor_clust(void *mem, int size, void *arg, int how)
{
struct mbuf *m;
u_int *refcnt;
int type;
uma_zone_t zone;
#ifdef INVARIANTS
trash_ctor(mem, size, arg, how);
#endif
switch (size) {
case MCLBYTES:
type = EXT_CLUSTER;
zone = zone_clust;
break;
#if MJUMPAGESIZE != MCLBYTES
case MJUMPAGESIZE:
type = EXT_JUMBOP;
zone = zone_jumbop;
break;
#endif
case MJUM9BYTES:
type = EXT_JUMBO9;
zone = zone_jumbo9;
break;
case MJUM16BYTES:
type = EXT_JUMBO16;
zone = zone_jumbo16;
break;
default:
panic("unknown cluster size");
break;
}
m = (struct mbuf *)arg;
refcnt = uma_find_refcnt(zone, mem);
*refcnt = 1;
if (m != NULL) {
m->m_ext.ext_buf = (caddr_t)mem;
m->m_data = m->m_ext.ext_buf;
m->m_flags |= M_EXT;
m->m_ext.ext_free = NULL;
m->m_ext.ext_arg1 = NULL;
m->m_ext.ext_arg2 = NULL;
m->m_ext.ext_size = size;
m->m_ext.ext_type = type;
m->m_ext.ext_flags = 0;
m->m_ext.ext_cnt = refcnt;
}
return (0);
}
/*
* The Mbuf Cluster zone destructor.
*/
static void
mb_dtor_clust(void *mem, int size, void *arg)
{
#ifdef INVARIANTS
uma_zone_t zone;
zone = m_getzone(size);
KASSERT(*(uma_find_refcnt(zone, mem)) <= 1,
("%s: refcnt incorrect %u", __func__,
*(uma_find_refcnt(zone, mem))) );
trash_dtor(mem, size, arg);
#endif
}
/*
* The Packet secondary zone's init routine, executed on the
* object's transition from mbuf keg slab to zone cache.
*/
static int
mb_zinit_pack(void *mem, int size, int how)
{
struct mbuf *m;
m = (struct mbuf *)mem; /* m is virgin. */
if (uma_zalloc_arg(zone_clust, m, how) == NULL ||
m->m_ext.ext_buf == NULL)
return (ENOMEM);
m->m_ext.ext_type = EXT_PACKET; /* Override. */
#ifdef INVARIANTS
trash_init(m->m_ext.ext_buf, MCLBYTES, how);
#endif
return (0);
}
/*
* The Packet secondary zone's fini routine, executed on the
* object's transition from zone cache to keg slab.
*/
static void
mb_zfini_pack(void *mem, int size)
{
struct mbuf *m;
m = (struct mbuf *)mem;
#ifdef INVARIANTS
trash_fini(m->m_ext.ext_buf, MCLBYTES);
#endif
uma_zfree_arg(zone_clust, m->m_ext.ext_buf, NULL);
#ifdef INVARIANTS
trash_dtor(mem, size, NULL);
#endif
}
/*
* The "packet" keg constructor.
*/
static int
mb_ctor_pack(void *mem, int size, void *arg, int how)
{
struct mbuf *m;
struct mb_args *args;
int error, flags;
short type;
m = (struct mbuf *)mem;
args = (struct mb_args *)arg;
flags = args->flags;
type = args->type;
#ifdef INVARIANTS
trash_ctor(m->m_ext.ext_buf, MCLBYTES, arg, how);
#endif
error = m_init(m, NULL, size, how, type, flags);
/* m_ext is already initialized. */
m->m_data = m->m_ext.ext_buf;
m->m_flags = (flags | M_EXT);
return (error);
}
int
m_pkthdr_init(struct mbuf *m, int how)
{
#ifdef MAC
int error;
#endif
m->m_data = m->m_pktdat;
bzero(&m->m_pkthdr, sizeof(m->m_pkthdr));
#ifdef MAC
/* If the label init fails, fail the alloc */
error = mac_mbuf_init(m, how);
if (error)
return (error);
#endif
return (0);
}
/*
* This is the protocol drain routine.
*
* No locks should be held when this is called. The drain routines have to
* presently acquire some locks which raises the possibility of lock order
* reversal.
*/
static void
mb_reclaim(void *junk)
{
struct domain *dp;
struct protosw *pr;
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK | WARN_PANIC, NULL,
"mb_reclaim()");
for (dp = domains; dp != NULL; dp = dp->dom_next)
for (pr = dp->dom_protosw; pr < dp->dom_protoswNPROTOSW; pr++)
if (pr->pr_drain != NULL)
(*pr->pr_drain)();
}