netisr.c revision 112011 
1/*-
2 * Copyright (c) 2001,2002,2003 Jonathan Lemon <jlemon@FreeBSD.org>
3 * Copyright (c) 1997, Stefan Esser <se@freebsd.org>
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 * 1. Redistributions of source code must retain the above copyright
10 *    notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
18 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
25 * SUCH DAMAGE.
26 *
27 * $FreeBSD: head/sys/net/netisr.c 112011 2003-03-08 22:12:32Z jlemon $
28 */
29
30#include <sys/param.h>
31#include <sys/bus.h>
32#include <sys/rtprio.h>
33#include <sys/systm.h>
34#include <sys/interrupt.h>
35#include <sys/kernel.h>
36#include <sys/kthread.h>
37#include <sys/lock.h>
38#include <sys/malloc.h>
39#include <sys/proc.h>
40#include <sys/random.h>
41#include <sys/resourcevar.h>
42#include <sys/sysctl.h>
43#include <sys/unistd.h>
44#include <machine/atomic.h>
45#include <machine/cpu.h>
46#include <machine/stdarg.h>
47
48#include <sys/mbuf.h>
49#include <sys/socket.h>
50
51#include <net/if.h>
52#include <net/if_types.h>
53#include <net/if_var.h>
54#include <net/netisr.h>
55
56volatile unsigned int	netisr;	/* scheduling bits for network */
57
58struct netisr {
59	netisr_t	*ni_handler;
60	struct ifqueue	*ni_queue;
61} netisrs[32];
62
63static struct mtx netisr_mtx;
64static void *net_ih;
65
66void
67legacy_setsoftnet(void)
68{
69	swi_sched(net_ih, 0);
70}
71
72void
73netisr_register(int num, netisr_t *handler, struct ifqueue *inq)
74{
75
76	KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
77	    ("bad isr %d", num));
78	netisrs[num].ni_handler = handler;
79	netisrs[num].ni_queue = inq;
80}
81
82void
83netisr_unregister(int num)
84{
85	struct netisr *ni;
86	int s;
87
88	KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
89	    ("bad isr %d", num));
90	ni = &netisrs[num];
91	ni->ni_handler = NULL;
92	if (ni->ni_queue != NULL) {
93		s = splimp();
94		IF_DRAIN(ni->ni_queue);
95		splx(s);
96	}
97}
98
99struct isrstat {
100	int	isrs_count;			/* dispatch count */
101	int	isrs_directed;			/* ...successfully dispatched */
102	int	isrs_deferred;			/* ...queued instead */
103	int	isrs_bypassed;			/* bypassed queued packets */
104	int	isrs_queued;			/* intentionally queueued */
105	int	isrs_swi_count;			/* swi_net handlers called */
106};
107static struct isrstat isrstat;
108
109SYSCTL_NODE(_net, OID_AUTO, isr, CTLFLAG_RW, 0, "netisr counters");
110
111static int	netisr_enable = 0;
112SYSCTL_INT(_net_isr, OID_AUTO, enable, CTLFLAG_RW,
113    &netisr_enable, 0, "enable direct dispatch");
114
115SYSCTL_INT(_net_isr, OID_AUTO, count, CTLFLAG_RD,
116    &isrstat.isrs_count, 0, "");
117SYSCTL_INT(_net_isr, OID_AUTO, directed, CTLFLAG_RD,
118    &isrstat.isrs_directed, 0, "");
119SYSCTL_INT(_net_isr, OID_AUTO, deferred, CTLFLAG_RD,
120    &isrstat.isrs_deferred, 0, "");
121SYSCTL_INT(_net_isr, OID_AUTO, bypassed, CTLFLAG_RD,
122    &isrstat.isrs_bypassed, 0, "");
123SYSCTL_INT(_net_isr, OID_AUTO, queued, CTLFLAG_RD,
124    &isrstat.isrs_queued, 0, "");
125SYSCTL_INT(_net_isr, OID_AUTO, swi_count, CTLFLAG_RD,
126    &isrstat.isrs_swi_count, 0, "");
127
128/*
129 * Call the netisr directly instead of queueing the packet, if possible.
130 *
131 * Ideally, the permissibility of calling the routine would be determined
132 * by checking if splnet() was asserted at the time the device interrupt
133 * occurred; if so, this indicates that someone is in the network stack.
134 *
135 * However, bus_setup_intr uses INTR_TYPE_NET, which sets splnet before
136 * calling the interrupt handler, so the previous mask is unavailable.
137 * Approximate this by checking intr_nesting_level instead; if any SWI
138 * handlers are running, the packet is queued instead.
139 */
140void
141netisr_dispatch(int num, struct mbuf *m)
142{
143	struct netisr *ni;
144
145	isrstat.isrs_count++;
146	KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
147	    ("bad isr %d", num));
148	ni = &netisrs[num];
149	if (ni->ni_queue == NULL) {
150		m_freem(m);
151		return;
152	}
153	if (netisr_enable && mtx_trylock(&netisr_mtx)) {
154		isrstat.isrs_directed++;
155		/*
156		 * One slight problem here is that packets might bypass
157		 * each other in the stack, if an earlier one happened
158		 * to get stuck in the queue.
159		 *
160		 * we can either:
161		 *	a. drain the queue before handling this packet,
162		 *	b. fallback to queueing the packet,
163		 *	c. sweep the issue under the rug and ignore it.
164		 *
165		 * Currently, we do c), and keep a rough event counter.
166		 */
167		if (_IF_QLEN(ni->ni_queue) > 0)
168			isrstat.isrs_bypassed++;
169		ni->ni_handler(m);
170		mtx_unlock(&netisr_mtx);
171	} else {
172		isrstat.isrs_deferred++;
173		if (IF_HANDOFF(ni->ni_queue, m, NULL))
174			schednetisr(num);
175	}
176}
177
178/*
179 * Same as above, but always queue.
180 * This is either used in places where we are not confident that
181 * direct dispatch is possible, or where queueing is required.
182 */
183int
184netisr_queue(int num, struct mbuf *m)
185{
186	struct netisr *ni;
187
188	KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
189	    ("bad isr %d", num));
190	ni = &netisrs[num];
191	if (ni->ni_queue == NULL) {
192		m_freem(m);
193		return (1);
194	}
195	isrstat.isrs_queued++;
196	if (!IF_HANDOFF(ni->ni_queue, m, NULL))
197		return (0);
198	schednetisr(num);
199	return (1);
200}
201
202static void
203swi_net(void *dummy)
204{
205	struct netisr *ni;
206	struct mbuf *m;
207	u_int bits;
208	int i;
209#ifdef DEVICE_POLLING
210	const int polling = 1;
211#else
212	const int polling = 0;
213#endif
214
215	mtx_lock(&netisr_mtx);
216	do {
217		bits = atomic_readandclear_int(&netisr);
218		if (bits == 0)
219			break;
220		while ((i = ffs(bits)) != 0) {
221			isrstat.isrs_swi_count++;
222			i--;
223			bits &= ~(1 << i);
224			ni = &netisrs[i];
225			if (ni->ni_handler == NULL) {
226				printf("swi_net: unregistered isr %d.\n", i);
227				continue;
228			}
229			if (ni->ni_queue == NULL)
230				ni->ni_handler(NULL);
231			else
232				for (;;) {
233					IF_DEQUEUE(ni->ni_queue, m);
234					if (m == NULL)
235						break;
236					ni->ni_handler(m);
237				}
238		}
239	} while (polling);
240	mtx_unlock(&netisr_mtx);
241}
242
243static void
244start_netisr(void *dummy)
245{
246
247	mtx_init(&netisr_mtx, "netisr lock", NULL, MTX_DEF);
248	if (swi_add(NULL, "net", swi_net, NULL, SWI_NET, 0, &net_ih))
249		panic("start_netisr");
250}
251SYSINIT(start_netisr, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_netisr, NULL)
252