FreeBSD/Linux Kernel Cross Reference
sys/net/netisr.c
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: releng/6.2/sys/net/netisr.c 151061 2005-10-07 14:00:06Z glebius $
28 */
29
30 #include "opt_device_polling.h"
31 #include "opt_net.h"
32
33 #include <sys/param.h>
34 #include <sys/bus.h>
35 #include <sys/rtprio.h>
36 #include <sys/systm.h>
37 #include <sys/interrupt.h>
38 #include <sys/kernel.h>
39 #include <sys/kthread.h>
40 #include <sys/lock.h>
41 #include <sys/malloc.h>
42 #include <sys/proc.h>
43 #include <sys/random.h>
44 #include <sys/resourcevar.h>
45 #include <sys/sysctl.h>
46 #include <sys/unistd.h>
47 #include <machine/atomic.h>
48 #include <machine/cpu.h>
49 #include <machine/stdarg.h>
50
51 #include <sys/mbuf.h>
52 #include <sys/socket.h>
53
54 #include <net/if.h>
55 #include <net/if_types.h>
56 #include <net/if_var.h>
57 #include <net/netisr.h>
58
59 /*
60 * debug_mpsafenet controls network subsystem-wide use of the Giant lock,
61 * from system calls down to interrupt handlers. It can be changed only via
62 * a tunable at boot, not at run-time, due to the complexity of unwinding.
63 * The compiled default is set via a kernel option; right now, the default
64 * unless otherwise specified is to run the network stack without Giant.
65 */
66 #ifdef NET_WITH_GIANT
67 int debug_mpsafenet = 0;
68 #else
69 int debug_mpsafenet = 1;
70 #endif
71 int debug_mpsafenet_toolatetotwiddle = 0;
72
73 TUNABLE_INT("debug.mpsafenet", &debug_mpsafenet);
74 SYSCTL_INT(_debug, OID_AUTO, mpsafenet, CTLFLAG_RD, &debug_mpsafenet, 0,
75 "Enable/disable MPSAFE network support");
76
77 volatile unsigned int netisr; /* scheduling bits for network */
78
79 struct netisr {
80 netisr_t *ni_handler;
81 struct ifqueue *ni_queue;
82 int ni_flags;
83 } netisrs[32];
84
85 static void *net_ih;
86
87 /*
88 * Not all network code is currently capable of running MPSAFE; however,
89 * most of it is. Since those sections that are not are generally optional
90 * components not shipped with default kernels, we provide a basic way to
91 * determine whether MPSAFE operation is permitted: based on a default of
92 * yes, we permit non-MPSAFE components to use a registration call to
93 * identify that they require Giant. If the system is early in the boot
94 * process still, then we change the debug_mpsafenet setting to choose a
95 * non-MPSAFE execution mode (degraded). If it's too late for that (since
96 * the setting cannot be changed at run time), we generate a console warning
97 * that the configuration may be unsafe.
98 */
99 static int mpsafe_warn_count;
100
101 /*
102 * Function call implementing registration of a non-MPSAFE network component.
103 */
104 void
105 net_warn_not_mpsafe(const char *component)
106 {
107
108 /*
109 * If we're running with Giant over the network stack, there is no
110 * problem.
111 */
112 if (!debug_mpsafenet)
113 return;
114
115 /*
116 * If it's not too late to change the MPSAFE setting for the network
117 * stack, do so now. This effectively suppresses warnings by
118 * components registering later.
119 */
120 if (!debug_mpsafenet_toolatetotwiddle) {
121 debug_mpsafenet = 0;
122 printf("WARNING: debug.mpsafenet forced to 0 as %s requires "
123 "Giant\n", component);
124 return;
125 }
126
127 /*
128 * We must run without Giant, so generate a console warning with some
129 * information with what to do about it. The system may be operating
130 * unsafely, however.
131 */
132 printf("WARNING: Network stack Giant-free, but %s requires Giant.\n",
133 component);
134 if (mpsafe_warn_count == 0)
135 printf(" Consider adding 'options NET_WITH_GIANT' or "
136 "setting debug.mpsafenet=0\n");
137 mpsafe_warn_count++;
138 }
139
140 /*
141 * This sysinit is run after any pre-loaded or compiled-in components have
142 * announced that they require Giant, but before any modules loaded at
143 * run-time.
144 */
145 static void
146 net_mpsafe_toolate(void *arg)
147 {
148
149 debug_mpsafenet_toolatetotwiddle = 1;
150
151 if (!debug_mpsafenet)
152 printf("WARNING: MPSAFE network stack disabled, expect "
153 "reduced performance.\n");
154 }
155
156 SYSINIT(net_mpsafe_toolate, SI_SUB_SETTINGS, SI_ORDER_ANY, net_mpsafe_toolate,
157 NULL);
158
159 void
160 legacy_setsoftnet(void)
161 {
162 swi_sched(net_ih, 0);
163 }
164
165 void
166 netisr_register(int num, netisr_t *handler, struct ifqueue *inq, int flags)
167 {
168
169 KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
170 ("bad isr %d", num));
171 netisrs[num].ni_handler = handler;
172 netisrs[num].ni_queue = inq;
173 if ((flags & NETISR_MPSAFE) && !debug_mpsafenet)
174 flags &= ~NETISR_MPSAFE;
175 netisrs[num].ni_flags = flags;
176 }
177
178 void
179 netisr_unregister(int num)
180 {
181 struct netisr *ni;
182
183 KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
184 ("bad isr %d", num));
185 ni = &netisrs[num];
186 ni->ni_handler = NULL;
187 if (ni->ni_queue != NULL)
188 IF_DRAIN(ni->ni_queue);
189 ni->ni_queue = NULL;
190 }
191
192 struct isrstat {
193 int isrs_count; /* dispatch count */
194 int isrs_directed; /* ...directly dispatched */
195 int isrs_deferred; /* ...queued instead */
196 int isrs_queued; /* intentionally queueued */
197 int isrs_drop; /* dropped 'cuz no handler */
198 int isrs_swi_count; /* swi_net handlers called */
199 };
200 static struct isrstat isrstat;
201
202 SYSCTL_NODE(_net, OID_AUTO, isr, CTLFLAG_RW, 0, "netisr counters");
203
204 static int netisr_direct = 0;
205 SYSCTL_INT(_net_isr, OID_AUTO, direct, CTLFLAG_RW,
206 &netisr_direct, 0, "enable direct dispatch");
207 TUNABLE_INT("net.isr.direct", &netisr_direct);
208
209 SYSCTL_INT(_net_isr, OID_AUTO, count, CTLFLAG_RD,
210 &isrstat.isrs_count, 0, "");
211 SYSCTL_INT(_net_isr, OID_AUTO, directed, CTLFLAG_RD,
212 &isrstat.isrs_directed, 0, "");
213 SYSCTL_INT(_net_isr, OID_AUTO, deferred, CTLFLAG_RD,
214 &isrstat.isrs_deferred, 0, "");
215 SYSCTL_INT(_net_isr, OID_AUTO, queued, CTLFLAG_RD,
216 &isrstat.isrs_queued, 0, "");
217 SYSCTL_INT(_net_isr, OID_AUTO, drop, CTLFLAG_RD,
218 &isrstat.isrs_drop, 0, "");
219 SYSCTL_INT(_net_isr, OID_AUTO, swi_count, CTLFLAG_RD,
220 &isrstat.isrs_swi_count, 0, "");
221
222 /*
223 * Process all packets currently present in a netisr queue. Used to
224 * drain an existing set of packets waiting for processing when we
225 * begin direct dispatch, to avoid processing packets out of order.
226 */
227 static void
228 netisr_processqueue(struct netisr *ni)
229 {
230 struct mbuf *m;
231
232 for (;;) {
233 IF_DEQUEUE(ni->ni_queue, m);
234 if (m == NULL)
235 break;
236 ni->ni_handler(m);
237 }
238 }
239
240 /*
241 * Call the netisr directly instead of queueing the packet, if possible.
242 */
243 void
244 netisr_dispatch(int num, struct mbuf *m)
245 {
246 struct netisr *ni;
247
248 isrstat.isrs_count++; /* XXX redundant */
249 KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
250 ("bad isr %d", num));
251 ni = &netisrs[num];
252 if (ni->ni_queue == NULL) {
253 isrstat.isrs_drop++;
254 m_freem(m);
255 return;
256 }
257 /*
258 * Do direct dispatch only for MPSAFE netisrs (and
259 * only when enabled). Note that when a netisr is
260 * marked MPSAFE we permit multiple concurrent instances
261 * to run. We guarantee only the order in which
262 * packets are processed for each "dispatch point" in
263 * the system (i.e. call to netisr_dispatch or
264 * netisr_queue). This insures ordering of packets
265 * from an interface but does not guarantee ordering
266 * between multiple places in the system (e.g. IP
267 * dispatched from interfaces vs. IP queued from IPSec).
268 */
269 if (netisr_direct && (ni->ni_flags & NETISR_MPSAFE)) {
270 isrstat.isrs_directed++;
271 /*
272 * NB: We used to drain the queue before handling
273 * the packet but now do not. Doing so here will
274 * not preserve ordering so instead we fallback to
275 * guaranteeing order only from dispatch points
276 * in the system (see above).
277 */
278 ni->ni_handler(m);
279 } else {
280 isrstat.isrs_deferred++;
281 if (IF_HANDOFF(ni->ni_queue, m, NULL))
282 schednetisr(num);
283 }
284 }
285
286 /*
287 * Same as above, but always queue.
288 * This is either used in places where we are not confident that
289 * direct dispatch is possible, or where queueing is required.
290 * It returns (0) on success and ERRNO on failure. On failure the
291 * mbuf has been free'd.
292 */
293 int
294 netisr_queue(int num, struct mbuf *m)
295 {
296 struct netisr *ni;
297
298 KASSERT(!(num < 0 || num >= (sizeof(netisrs)/sizeof(*netisrs))),
299 ("bad isr %d", num));
300 ni = &netisrs[num];
301 if (ni->ni_queue == NULL) {
302 isrstat.isrs_drop++;
303 m_freem(m);
304 return (ENXIO);
305 }
306 isrstat.isrs_queued++;
307 if (!IF_HANDOFF(ni->ni_queue, m, NULL))
308 return (ENOBUFS); /* IF_HANDOFF has free'd the mbuf */
309 schednetisr(num);
310 return (0);
311 }
312
313 static void
314 swi_net(void *dummy)
315 {
316 struct netisr *ni;
317 u_int bits;
318 int i;
319 #ifdef DEVICE_POLLING
320 const int polling = 1;
321 #else
322 const int polling = 0;
323 #endif
324
325 do {
326 bits = atomic_readandclear_int(&netisr);
327 if (bits == 0)
328 break;
329 while ((i = ffs(bits)) != 0) {
330 isrstat.isrs_swi_count++;
331 i--;
332 bits &= ~(1 << i);
333 ni = &netisrs[i];
334 if (ni->ni_handler == NULL) {
335 printf("swi_net: unregistered isr %d.\n", i);
336 continue;
337 }
338 if ((ni->ni_flags & NETISR_MPSAFE) == 0) {
339 mtx_lock(&Giant);
340 if (ni->ni_queue == NULL)
341 ni->ni_handler(NULL);
342 else
343 netisr_processqueue(ni);
344 mtx_unlock(&Giant);
345 } else {
346 if (ni->ni_queue == NULL)
347 ni->ni_handler(NULL);
348 else
349 netisr_processqueue(ni);
350 }
351 }
352 } while (polling);
353 }
354
355 static void
356 start_netisr(void *dummy)
357 {
358
359 if (swi_add(NULL, "net", swi_net, NULL, SWI_NET, INTR_MPSAFE, &net_ih))
360 panic("start_netisr");
361 }
362 SYSINIT(start_netisr, SI_SUB_SOFTINTR, SI_ORDER_FIRST, start_netisr, NULL)
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