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
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.
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.
45 #include <sys/param.h>
46 #include <sys/systm.h>
47 #include <sys/kernel.h>
49 #include <sys/rtprio.h>
50 #include <sys/queue.h>
51 #include <sys/thread2.h>
52 #include <sys/serialize.h>
53 #include <sys/sysctl.h>
55 #include <sys/kthread.h>
56 #include <machine/cpu.h>
57 #include <machine/cpufunc.h>
58 #include <machine/specialreg.h>
67 #define SLZ_KTR_STRING "slz=%p"
68 #define SLZ_KTR_ARGS lwkt_serialize_t slz
70 #ifndef KTR_SERIALIZER
71 #define KTR_SERIALIZER KTR_ALL
75 KTR_INFO(KTR_SERIALIZER, slz, enter_beg, 0, SLZ_KTR_STRING, SLZ_KTR_ARGS);
76 KTR_INFO(KTR_SERIALIZER, slz, sleep_beg, 1, SLZ_KTR_STRING, SLZ_KTR_ARGS);
77 KTR_INFO(KTR_SERIALIZER, slz, sleep_end, 2, SLZ_KTR_STRING, SLZ_KTR_ARGS);
78 KTR_INFO(KTR_SERIALIZER, slz, exit_end, 3, SLZ_KTR_STRING, SLZ_KTR_ARGS);
79 KTR_INFO(KTR_SERIALIZER, slz, wakeup_beg, 4, SLZ_KTR_STRING, SLZ_KTR_ARGS);
80 KTR_INFO(KTR_SERIALIZER, slz, wakeup_end, 5, SLZ_KTR_STRING, SLZ_KTR_ARGS);
81 KTR_INFO(KTR_SERIALIZER, slz, try, 6, SLZ_KTR_STRING, SLZ_KTR_ARGS);
82 KTR_INFO(KTR_SERIALIZER, slz, tryfail, 7, SLZ_KTR_STRING, SLZ_KTR_ARGS);
83 KTR_INFO(KTR_SERIALIZER, slz, tryok, 8, SLZ_KTR_STRING, SLZ_KTR_ARGS);
85 KTR_INFO(KTR_SERIALIZER, slz, spinbo, 9,
86 "slz=%p bo1=%d bo=%d", lwkt_serialize_t slz, int backoff1, int backoff);
88 KTR_INFO(KTR_SERIALIZER, slz, enter_end, 10, SLZ_KTR_STRING, SLZ_KTR_ARGS);
89 KTR_INFO(KTR_SERIALIZER, slz, exit_beg, 11, SLZ_KTR_STRING, SLZ_KTR_ARGS);
91 #define logslz(name, slz) KTR_LOG(slz_ ## name, slz)
93 #define logslz_spinbo(slz, bo1, bo) KTR_LOG(slz_spinbo, slz, bo1, bo)
96 static void lwkt_serialize_sleep(void *info);
97 static void lwkt_serialize_wakeup(void *info);
100 static void lwkt_serialize_adaptive_sleep(void *bo);
102 static int slz_backoff_limit = 128;
103 SYSCTL_INT(_debug, OID_AUTO, serialize_bolimit, CTLFLAG_RW,
104 &slz_backoff_limit, 0, "Backoff limit");
106 static int slz_backoff_shift = 1;
107 SYSCTL_INT(_debug, OID_AUTO, serialize_boshift, CTLFLAG_RW,
108 &slz_backoff_shift, 0, "Backoff shift");
110 static int slz_backoff_round;
111 TUNABLE_INT("debug.serialize_boround", &slz_backoff_round);
112 SYSCTL_INT(_debug, OID_AUTO, serialize_boround, CTLFLAG_RW,
113 &slz_backoff_round, 0,
118 lwkt_serialize_init(lwkt_serialize_t s)
120 atomic_intr_init(&s->interlock);
122 s->last_td = (void *)-4;
128 lwkt_serialize_adaptive_enter(lwkt_serialize_t s)
130 struct exp_backoff bo;
136 ASSERT_NOT_SERIALIZED(s);
138 logslz(enter_beg, s);
139 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_adaptive_sleep, &bo);
140 logslz(enter_end, s);
142 s->last_td = curthread;
148 lwkt_serialize_enter(lwkt_serialize_t s)
150 ASSERT_NOT_SERIALIZED(s);
152 logslz(enter_beg, s);
153 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
154 logslz(enter_end, s);
156 s->last_td = curthread;
161 * Returns non-zero on success
164 lwkt_serialize_try(lwkt_serialize_t s)
168 ASSERT_NOT_SERIALIZED(s);
171 if ((error = atomic_intr_cond_try(&s->interlock)) == 0) {
173 s->last_td = curthread;
183 lwkt_serialize_exit(lwkt_serialize_t s)
185 ASSERT_SERIALIZED(s);
187 s->last_td = (void *)-2;
190 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
195 * Interrupt handler disablement support, used by drivers. Non-stackable
199 lwkt_serialize_handler_disable(lwkt_serialize_t s)
201 atomic_intr_handler_disable(&s->interlock);
205 lwkt_serialize_handler_enable(lwkt_serialize_t s)
207 atomic_intr_handler_enable(&s->interlock);
211 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *),
212 void *arg, void *frame)
215 * note: a return value of 0 indicates that the interrupt handler is
218 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
219 logslz(enter_beg, s);
220 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
221 logslz(enter_end, s);
223 s->last_td = curthread;
225 if (atomic_intr_handler_is_enabled(&s->interlock) == 0)
228 ASSERT_SERIALIZED(s);
230 s->last_td = (void *)-2;
233 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
239 * Similar to handler_call but does not block. Returns 0 on success,
243 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *),
244 void *arg, void *frame)
247 * note: a return value of 0 indicates that the interrupt handler is
250 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
252 if (atomic_intr_cond_try(&s->interlock) == 0) {
254 s->last_td = curthread;
260 ASSERT_SERIALIZED(s);
262 s->last_td = (void *)-2;
265 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
278 * It is possible to race an interrupt which acquires and releases the
279 * bit, then calls wakeup before we actually go to sleep, so we
280 * need to check that the interlock is still acquired from within
281 * a critical section prior to sleeping.
284 lwkt_serialize_sleep(void *info)
286 lwkt_serialize_t s = info;
288 tsleep_interlock(s, 0);
289 if (atomic_intr_cond_test(&s->interlock) != 0) {
290 logslz(sleep_beg, s);
291 tsleep(s, PINTERLOCKED, "slize", 0);
292 logslz(sleep_end, s);
299 lwkt_serialize_adaptive_sleep(void *arg)
301 struct exp_backoff *bo = arg;
302 lwkt_serialize_t s = bo->s;
306 * Randomize backoff value
308 #ifdef _RDTSC_SUPPORTED_
309 if (cpu_feature & CPUID_TSC) {
311 (((u_long)rdtsc() ^ (((u_long)curthread) >> 5)) &
312 (bo->backoff - 1)) + 1;
315 backoff = bo->backoff;
317 logslz_spinbo(s, bo->backoff, backoff);
322 for (; backoff; --backoff)
324 if (bo->backoff < slz_backoff_limit) {
325 bo->backoff <<= slz_backoff_shift;
330 if (bo->round >= slz_backoff_round)
336 tsleep_interlock(s, 0);
337 if (atomic_intr_cond_test(&s->interlock) != 0) {
338 logslz(sleep_beg, s);
339 tsleep(s, PINTERLOCKED, "slize", 0);
340 logslz(sleep_end, s);
347 lwkt_serialize_wakeup(void *info)
349 logslz(wakeup_beg, info);
351 logslz(wakeup_end, info);
356 lwkt_serialize_sysinit(void *dummy __unused)
358 if (slz_backoff_round <= 0)
359 slz_backoff_round = ncpus * 2;
361 SYSINIT(lwkt_serialize, SI_SUB_PRE_DRIVERS, SI_ORDER_SECOND,
362 lwkt_serialize_sysinit, NULL);