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59dd72d040
dispatched without Giant, and add NETISR_FORCEQUEUE, which allows specific netisr handlers to always be dispatched via a queue (deferred). Mark the usb and if_ppp netisr handlers as NETISR_FORCEQUEUE, and explicitly acquire Giant in those handlers. Previously, any netisr handler not marked NETISR_MPSAFE would necessarily run deferred and with Giant acquired. This change removes Giant scaffolding from the netisr infrastructure, but NETISR_FORCEQUEUE allows non-MPSAFE handlers to continue to force deferred dispatch so as to avoid lock order reversals between their acqusition of Giant and any calling context. It is likely we will be able to remove NETISR_FORCEQUEUE once IFF_NEEDSGIANT is removed, as non-MPSAFE usb and if_ppp drivers will no longer be supported. Reviewed by: bz MFC after: 1 month X-MFC note: We can't remove NETISR_MPSAFE from stable/7 for KPI reasons, but the rest can go back.
254 lines
6.8 KiB
C
254 lines
6.8 KiB
C
/*-
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* Copyright (c) 2001,2002,2003 Jonathan Lemon <jlemon@FreeBSD.org>
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* Copyright (c) 1997, Stefan Esser <se@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#include "opt_device_polling.h"
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#include <sys/param.h>
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#include <sys/bus.h>
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#include <sys/rtprio.h>
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#include <sys/systm.h>
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#include <sys/interrupt.h>
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#include <sys/kernel.h>
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#include <sys/kthread.h>
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#include <sys/lock.h>
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#include <sys/malloc.h>
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#include <sys/proc.h>
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#include <sys/random.h>
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#include <sys/resourcevar.h>
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#include <sys/sysctl.h>
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#include <sys/unistd.h>
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#include <machine/atomic.h>
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#include <machine/cpu.h>
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#include <machine/stdarg.h>
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#include <sys/mbuf.h>
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#include <sys/socket.h>
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#include <net/if.h>
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#include <net/if_types.h>
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#include <net/if_var.h>
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#include <net/netisr.h>
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volatile unsigned int netisr; /* scheduling bits for network */
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struct netisr {
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netisr_t *ni_handler;
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struct ifqueue *ni_queue;
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int ni_flags;
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} netisrs[32];
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static void *net_ih;
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void
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legacy_setsoftnet(void)
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{
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swi_sched(net_ih, 0);
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}
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void
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netisr_register(int num, netisr_t *handler, struct ifqueue *inq, int flags)
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{
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KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
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("bad isr %d", num));
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KASSERT(flags == 0 || flags == NETISR_FORCEQUEUE,
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("netisr_register: bad flags 0x%x\n", flags));
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netisrs[num].ni_handler = handler;
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netisrs[num].ni_queue = inq;
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netisrs[num].ni_flags = flags;
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}
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void
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netisr_unregister(int num)
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{
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struct netisr *ni;
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KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
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("bad isr %d", num));
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ni = &netisrs[num];
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ni->ni_handler = NULL;
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if (ni->ni_queue != NULL)
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IF_DRAIN(ni->ni_queue);
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ni->ni_queue = NULL;
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}
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struct isrstat {
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int isrs_count; /* dispatch count */
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int isrs_directed; /* ...directly dispatched */
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int isrs_deferred; /* ...queued instead */
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int isrs_queued; /* intentionally queueued */
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int isrs_drop; /* dropped 'cuz no handler */
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int isrs_swi_count; /* swi_net handlers called */
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};
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static struct isrstat isrstat;
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SYSCTL_NODE(_net, OID_AUTO, isr, CTLFLAG_RW, 0, "netisr counters");
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static int netisr_direct = 1;
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SYSCTL_INT(_net_isr, OID_AUTO, direct, CTLFLAG_RW,
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&netisr_direct, 0, "enable direct dispatch");
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TUNABLE_INT("net.isr.direct", &netisr_direct);
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SYSCTL_INT(_net_isr, OID_AUTO, count, CTLFLAG_RD,
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&isrstat.isrs_count, 0, "");
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SYSCTL_INT(_net_isr, OID_AUTO, directed, CTLFLAG_RD,
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&isrstat.isrs_directed, 0, "");
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SYSCTL_INT(_net_isr, OID_AUTO, deferred, CTLFLAG_RD,
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&isrstat.isrs_deferred, 0, "");
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SYSCTL_INT(_net_isr, OID_AUTO, queued, CTLFLAG_RD,
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&isrstat.isrs_queued, 0, "");
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SYSCTL_INT(_net_isr, OID_AUTO, drop, CTLFLAG_RD,
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&isrstat.isrs_drop, 0, "");
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SYSCTL_INT(_net_isr, OID_AUTO, swi_count, CTLFLAG_RD,
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&isrstat.isrs_swi_count, 0, "");
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/*
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* Process all packets currently present in a netisr queue. Used to
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* drain an existing set of packets waiting for processing when we
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* begin direct dispatch, to avoid processing packets out of order.
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*/
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static void
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netisr_processqueue(struct netisr *ni)
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{
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struct mbuf *m;
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for (;;) {
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IF_DEQUEUE(ni->ni_queue, m);
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if (m == NULL)
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break;
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ni->ni_handler(m);
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}
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}
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/*
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* Call the netisr directly instead of queueing the packet, if possible.
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*/
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void
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netisr_dispatch(int num, struct mbuf *m)
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{
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struct netisr *ni;
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isrstat.isrs_count++; /* XXX redundant */
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KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
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("bad isr %d", num));
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ni = &netisrs[num];
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if (ni->ni_queue == NULL) {
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isrstat.isrs_drop++;
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m_freem(m);
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return;
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}
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/*
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* Unless NETISR_FORCEQUEUE is set on the netisr (generally
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* indicating that the handler still requires Giant, which cannot be
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* acquired in arbitrary order with respect to a caller), directly
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* dispatch handling of this packet. Source ordering is maintained
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* by virtue of callers consistently calling one of queued or direct
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* dispatch, and the forcequeue flag being immutable after
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* registration.
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*/
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if (netisr_direct && !(ni->ni_flags & NETISR_FORCEQUEUE)) {
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isrstat.isrs_directed++;
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ni->ni_handler(m);
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} else {
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isrstat.isrs_deferred++;
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if (IF_HANDOFF(ni->ni_queue, m, NULL))
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schednetisr(num);
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}
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}
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/*
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* Same as above, but always queue.
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* This is either used in places where we are not confident that
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* direct dispatch is possible, or where queueing is required.
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* It returns (0) on success and ERRNO on failure. On failure the
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* mbuf has been free'd.
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*/
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int
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netisr_queue(int num, struct mbuf *m)
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{
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struct netisr *ni;
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KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
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("bad isr %d", num));
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ni = &netisrs[num];
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if (ni->ni_queue == NULL) {
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isrstat.isrs_drop++;
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m_freem(m);
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return (ENXIO);
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}
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isrstat.isrs_queued++;
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if (!IF_HANDOFF(ni->ni_queue, m, NULL))
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return (ENOBUFS); /* IF_HANDOFF has free'd the mbuf */
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schednetisr(num);
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return (0);
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}
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static void
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swi_net(void *dummy)
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{
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struct netisr *ni;
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u_int bits;
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int i;
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#ifdef DEVICE_POLLING
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const int polling = 1;
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#else
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const int polling = 0;
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#endif
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do {
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bits = atomic_readandclear_int(&netisr);
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if (bits == 0)
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break;
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while ((i = ffs(bits)) != 0) {
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isrstat.isrs_swi_count++;
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i--;
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bits &= ~(1 << i);
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ni = &netisrs[i];
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if (ni->ni_handler == NULL) {
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printf("swi_net: unregistered isr %d.\n", i);
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continue;
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}
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if (ni->ni_queue == NULL)
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ni->ni_handler(NULL);
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else
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netisr_processqueue(ni);
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}
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} while (polling);
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}
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static void
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start_netisr(void *dummy)
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{
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if (swi_add(NULL, "net", swi_net, NULL, SWI_NET, INTR_MPSAFE, &net_ih))
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panic("start_netisr");
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}
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SYSINIT(start_netisr, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_netisr, NULL);
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