1 /*
2 * Copyright (c) 2005 The DragonFly Project. All rights reserved.
3 *
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 *
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in
15 * the documentation and/or other materials provided with the
16 * distribution.
17 * 3. Neither the name of The DragonFly Project nor the names of its
18 * contributors may be used to endorse or promote products derived
19 * from this software without specific, prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34 /*
35 * This API provides a fast locked-bus-cycle-based serializer. It's
36 * basically a low level NON-RECURSIVE exclusive lock that can be held across
37 * a blocking condition. It is NOT a mutex.
38 *
39 * This serializer is primarily designed for low level situations and
40 * interrupt/device interaction. There are two primary facilities. First,
41 * the serializer facility itself. Second, an integrated interrupt handler
42 * disablement facility.
43 */
44
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/kernel.h>
48 #include <sys/proc.h>
49 #include <sys/rtprio.h>
50 #include <sys/queue.h>
51 #include <sys/serialize.h>
52 #include <sys/sysctl.h>
53 #include <sys/ktr.h>
54 #include <sys/kthread.h>
55 #include <machine/cpu.h>
56 #include <machine/cpufunc.h>
57 #include <machine/specialreg.h>
58 #include <machine/clock.h>
59 #include <sys/lock.h>
60
61 #ifndef SLZ_ADAPTIVE_SPINMAX
62 #define SLZ_ADAPTIVE_SPINMAX 4096
63 #endif
64
65 #define SLZ_KTR_STRING "slz=%p"
66 #define SLZ_KTR_ARGS lwkt_serialize_t slz
67
68 #ifndef KTR_SERIALIZER
69 #define KTR_SERIALIZER KTR_ALL
70 #endif
71
72 KTR_INFO_MASTER(slz);
73 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARGS);
74 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS);
75 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS);
76 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS);
77 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS);
78 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS);
79 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS);
80 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS);
81 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS);
82 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 9, SLZ_KTR_STRING, SLZ_KTR_ARGS);
83 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS);
84 KTR_INFO(KTR_SERIALIZER, slz, adapt_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS);
85 KTR_INFO(KTR_SERIALIZER, slz, adapt_end, 12, SLZ_KTR_STRING, SLZ_KTR_ARGS);
86 KTR_INFO(KTR_SERIALIZER, slz, adapt_spinend, 13, "slz=%p try=%d",
87 lwkt_serialize_t slz, int try);
88 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepb, 14, SLZ_KTR_STRING, SLZ_KTR_ARGS);
89 KTR_INFO(KTR_SERIALIZER, slz, adapt_sleepe, 15, SLZ_KTR_STRING, SLZ_KTR_ARGS);
90
91 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz)
92 #define logslz_spinend(slz, try) KTR_LOG(slz_adapt_spinend, slz, try)
93
94 static void lwkt_serialize_sleep(void *info);
95 static void lwkt_serialize_wakeup(void *info);
96
97 void
lwkt_serialize_init(lwkt_serialize_t s)98 lwkt_serialize_init(lwkt_serialize_t s)
99 {
100 atomic_intr_init(&s->interlock);
101 s->last_td = (void *)-4;
102 }
103
104 void
lwkt_serialize_enter(lwkt_serialize_t s)105 lwkt_serialize_enter(lwkt_serialize_t s)
106 {
107 ASSERT_NOT_SERIALIZED(s);
108
109 logslz(enter_beg, s);
110 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
111 logslz(enter_end, s);
112 s->last_td = curthread;
113 }
114
115 /*
116 * Returns non-zero on success
117 */
118 int
lwkt_serialize_try(lwkt_serialize_t s)119 lwkt_serialize_try(lwkt_serialize_t s)
120 {
121 int error;
122
123 ASSERT_NOT_SERIALIZED(s);
124
125 logslz(try, s);
126 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) {
127 s->last_td = curthread;
128 logslz(tryok, s);
129 return(1);
130 }
131 logslz(tryfail, s);
132 return (0);
133 }
134
135 void
lwkt_serialize_exit(lwkt_serialize_t s)136 lwkt_serialize_exit(lwkt_serialize_t s)
137 {
138 ASSERT_SERIALIZED(s);
139 s->last_td = (void *)-2;
140 logslz(exit_beg, s);
141 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
142 logslz(exit_end, s);
143 }
144
145 /*
146 * Interrupt handler disablement support, used by drivers. Non-stackable
147 * (uses bit 30).
148 */
149 void
lwkt_serialize_handler_disable(lwkt_serialize_t s)150 lwkt_serialize_handler_disable(lwkt_serialize_t s)
151 {
152 atomic_intr_handler_disable(&s->interlock);
153 }
154
155 void
lwkt_serialize_handler_enable(lwkt_serialize_t s)156 lwkt_serialize_handler_enable(lwkt_serialize_t s)
157 {
158 atomic_intr_handler_enable(&s->interlock);
159 }
160
161 void
lwkt_serialize_handler_call(lwkt_serialize_t s,void (* func)(void *,void *),void * arg,void * frame)162 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *),
163 void *arg, void *frame)
164 {
165 /*
166 * note: a return value of 0 indicates that the interrupt handler is
167 * enabled.
168 */
169 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
170 logslz(enter_beg, s);
171 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
172 logslz(enter_end, s);
173 s->last_td = curthread;
174 if (atomic_intr_handler_is_enabled(&s->interlock) == 0)
175 func(arg, frame);
176
177 ASSERT_SERIALIZED(s);
178 s->last_td = (void *)-2;
179 logslz(exit_beg, s);
180 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
181 logslz(exit_end, s);
182 }
183 }
184
185 /*
186 * Similar to handler_call but does not block. Returns 0 on success,
187 * and 1 on failure.
188 */
189 int
lwkt_serialize_handler_try(lwkt_serialize_t s,void (* func)(void *,void *),void * arg,void * frame)190 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *),
191 void *arg, void *frame)
192 {
193 /*
194 * note: a return value of 0 indicates that the interrupt handler is
195 * enabled.
196 */
197 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
198 logslz(try, s);
199 if (atomic_intr_cond_try(&s->interlock) == 0) {
200 s->last_td = curthread;
201 logslz(tryok, s);
202
203 func(arg, frame);
204
205 ASSERT_SERIALIZED(s);
206 s->last_td = (void *)-2;
207 logslz(exit_beg, s);
208 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
209 logslz(exit_end, s);
210 return(0);
211 }
212 }
213 logslz(tryfail, s);
214 return(1);
215 }
216
217
218 /*
219 * Helper functions
220 *
221 * It is possible to race an interrupt which acquires and releases the
222 * bit, then calls wakeup before we actually go to sleep, so we
223 * need to check that the interlock is still acquired from within
224 * a critical section prior to sleeping.
225 */
226 static void
lwkt_serialize_sleep(void * info)227 lwkt_serialize_sleep(void *info)
228 {
229 lwkt_serialize_t s = info;
230
231 tsleep_interlock(s, 0);
232 if (atomic_intr_cond_test(&s->interlock) != 0) {
233 logslz(sleep_beg, s);
234 tsleep(s, PINTERLOCKED, "slize", 0);
235 logslz(sleep_end, s);
236 }
237 }
238
239 void
lwkt_serialize_adaptive_enter(lwkt_serialize_t s)240 lwkt_serialize_adaptive_enter(lwkt_serialize_t s)
241 {
242 int try;
243
244 ASSERT_NOT_SERIALIZED(s);
245 logslz(adapt_beg, s);
246
247 if (atomic_intr_cond_try(&s->interlock) == 0) {
248 s->last_td = curthread;
249 logslz(adapt_end, s);
250 return;
251 }
252
253 restart:
254 /*
255 * Spinning a little bit, before going to sleep
256 *
257 * See the comment before kern/kern_spinlock.c
258 * _spin_lock_contested() about why atomic_intr_cond_test()
259 * is called first. atomic_intr_cond_test() contains
260 * _no_ MPLOCKED intruction.
261 */
262 for (try = SLZ_ADAPTIVE_SPINMAX; try; --try) {
263 if (atomic_intr_cond_test(&s->interlock) == 0 &&
264 atomic_intr_cond_try(&s->interlock) == 0) {
265 s->last_td = curthread;
266 logslz_spinend(s, try);
267 return;
268 }
269 }
270
271 atomic_intr_cond_inc(&s->interlock);
272
273 tsleep_interlock(s, 0);
274 if (atomic_intr_cond_try(&s->interlock) == 0) {
275 atomic_intr_cond_dec(&s->interlock);
276 s->last_td = curthread;
277 logslz_spinend(s, 0);
278 return;
279 } else {
280 logslz(adapt_sleepb, s);
281 tsleep(s, PINTERLOCKED, "aslize", 0);
282 logslz(adapt_sleepe, s);
283
284 atomic_intr_cond_dec(&s->interlock);
285 goto restart;
286 }
287 }
288
289 static void
lwkt_serialize_wakeup(void * info)290 lwkt_serialize_wakeup(void *info)
291 {
292 logslz(wakeup_beg, info);
293 wakeup(info);
294 logslz(wakeup_end, info);
295 }
296