2 * Copyright (c) 2005 The DragonFly Project. All rights reserved.
4 * This code is derived from software contributed to The DragonFly Project
5 * by Matthew Dillon <dillon@backplane.com>
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
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
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.
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
34 * $DragonFly: src/sys/kern/lwkt_serialize.c,v 1.15 2008/05/05 12:35:03 sephe Exp $
37 * This API provides a fast locked-bus-cycle-based serializer. It's
38 * basically a low level NON-RECURSIVE exclusive lock that can be held across
39 * a blocking condition. It is NOT a mutex.
41 * This serializer is primarily designed for low level situations and
42 * interrupt/device interaction. There are two primary facilities. First,
43 * the serializer facility itself. Second, an integrated interrupt handler
44 * disablement facility.
47 #include "opt_serializer.h"
49 #include <sys/param.h>
50 #include <sys/systm.h>
51 #include <sys/kernel.h>
53 #include <sys/rtprio.h>
54 #include <sys/queue.h>
55 #include <sys/thread2.h>
56 #include <sys/serialize.h>
57 #include <sys/sysctl.h>
59 #include <sys/kthread.h>
60 #include <machine/cpu.h>
61 #include <machine/cpufunc.h>
62 #include <machine/specialreg.h>
72 #define SLZ_KTR_STRING "slz=%p"
73 #define SLZ_KTR_ARG_SIZE (sizeof(void *))
75 #ifndef KTR_SERIALIZER
76 #define KTR_SERIALIZER KTR_ALL
80 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
81 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
82 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
83 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
84 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
85 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
86 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
87 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
88 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
89 KTR_INFO(KTR_SERIALIZER, slz, spinbo, 9,
90 "slz=%p bo1=%d bo=%d", (sizeof(void *) + (2 * sizeof(int))));
91 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 10, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
92 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARG_SIZE);
94 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz)
95 #define logslz_spinbo(slz, bo1, bo) KTR_LOG(slz_spinbo, slz, bo1, bo)
97 static void lwkt_serialize_sleep(void *info);
99 static void lwkt_serialize_adaptive_sleep(void *bo);
101 static void lwkt_serialize_wakeup(void *info);
104 static int slz_backoff_limit = 128;
105 SYSCTL_INT(_debug, OID_AUTO, serialize_bolimit, CTLFLAG_RW,
106 &slz_backoff_limit, 0, "");
108 static int slz_backoff_shift = 1;
109 SYSCTL_INT(_debug, OID_AUTO, serialize_boshift, CTLFLAG_RW,
110 &slz_backoff_shift, 0, "");
112 static int slz_backoff_round;
113 TUNABLE_INT("debug.serialize_boround", &slz_backoff_round);
114 SYSCTL_INT(_debug, OID_AUTO, serialize_boround, CTLFLAG_RW,
115 &slz_backoff_round, 0, "");
119 lwkt_serialize_init(lwkt_serialize_t s)
121 atomic_intr_init(&s->interlock);
123 s->last_td = (void *)-4;
134 lwkt_serialize_adaptive_enter(lwkt_serialize_t s)
136 struct exp_backoff bo;
143 KKASSERT(s->last_td != curthread);
145 logslz(enter_beg, s);
146 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_adaptive_sleep, &bo);
147 logslz(enter_end, s);
149 s->last_td = curthread;
151 #ifdef PROFILE_SERIALIZER
159 lwkt_serialize_enter(lwkt_serialize_t s)
162 KKASSERT(s->last_td != curthread);
164 logslz(enter_beg, s);
165 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
166 logslz(enter_end, s);
168 s->last_td = curthread;
170 #ifdef PROFILE_SERIALIZER
176 * Returns non-zero on success
179 lwkt_serialize_try(lwkt_serialize_t s)
184 KKASSERT(s->last_td != curthread);
186 #ifdef PROFILE_SERIALIZER
190 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) {
192 s->last_td = curthread;
197 #ifdef PROFILE_SERIALIZER
205 lwkt_serialize_exit(lwkt_serialize_t s)
208 KKASSERT(s->last_td == curthread);
209 s->last_td = (void *)-2;
212 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
217 * Interrupt handler disablement support, used by drivers. Non-stackable
221 lwkt_serialize_handler_disable(lwkt_serialize_t s)
223 atomic_intr_handler_disable(&s->interlock);
227 lwkt_serialize_handler_enable(lwkt_serialize_t s)
229 atomic_intr_handler_enable(&s->interlock);
233 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *),
234 void *arg, void *frame)
237 * note: a return value of 0 indicates that the interrupt handler is
240 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
241 logslz(enter_beg, s);
242 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
243 logslz(enter_end, s);
245 s->last_td = curthread;
247 #ifdef PROFILE_SERIALIZER
250 if (atomic_intr_handler_is_enabled(&s->interlock) == 0)
253 KKASSERT(s->last_td == curthread);
254 s->last_td = (void *)-2;
257 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
263 * Similar to handler_call but does not block. Returns 0 on success,
267 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *),
268 void *arg, void *frame)
271 * note: a return value of 0 indicates that the interrupt handler is
274 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
275 #ifdef PROFILE_SERIALIZER
279 if (atomic_intr_cond_try(&s->interlock) == 0) {
281 s->last_td = curthread;
286 KKASSERT(s->last_td == curthread);
287 s->last_td = (void *)-2;
290 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
295 #ifdef PROFILE_SERIALIZER
306 * It is possible to race an interrupt which acquires and releases the
307 * bit, then calls wakeup before we actually go to sleep, so we
308 * need to check that the interlock is still acquired from within
309 * a critical section prior to sleeping.
312 lwkt_serialize_sleep(void *info)
314 lwkt_serialize_t s = info;
317 if (atomic_intr_cond_test(&s->interlock) != 0) {
318 #ifdef PROFILE_SERIALIZER
321 logslz(sleep_beg, s);
322 tsleep(s, 0, "slize", 0);
323 logslz(sleep_end, s);
331 lwkt_serialize_adaptive_sleep(void *arg)
333 struct exp_backoff *bo = arg;
334 lwkt_serialize_t s = bo->s;
338 * Randomize backoff value
340 #ifdef _RDTSC_SUPPORTED_
341 if (cpu_feature & CPUID_TSC) {
343 (((u_long)rdtsc() ^ (((u_long)curthread) >> 5)) &
344 (bo->backoff - 1)) + 1;
347 backoff = bo->backoff;
349 logslz_spinbo(s, bo->backoff, backoff);
354 for (; backoff; --backoff)
356 if (bo->backoff < slz_backoff_limit) {
357 bo->backoff <<= slz_backoff_shift;
362 if (bo->round >= slz_backoff_round)
370 if (atomic_intr_cond_test(&s->interlock) != 0) {
371 #ifdef PROFILE_SERIALIZER
374 logslz(sleep_beg, s);
375 tsleep(s, 0, "slize", 0);
376 logslz(sleep_end, s);
384 lwkt_serialize_wakeup(void *info)
386 logslz(wakeup_beg, info);
388 logslz(wakeup_end, info);
393 lwkt_serialize_sysinit(void *dummy __unused)
395 if (slz_backoff_round <= 0)
396 slz_backoff_round = ncpus * 2;
398 SYSINIT(lwkt_serialize, SI_SUB_PRE_DRIVERS, SI_ORDER_SECOND,
399 lwkt_serialize_sysinit, NULL);