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 1.5 2005/09/12 21:40:24 dillon 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 <sys/param.h>
48 #include <sys/systm.h>
49 #include <sys/kernel.h>
51 #include <sys/rtprio.h>
52 #include <sys/queue.h>
53 #include <sys/thread2.h>
54 #include <sys/serialize.h>
55 #include <sys/sysctl.h>
56 #include <sys/kthread.h>
57 #include <machine/cpu.h>
61 static void lwkt_serialize_sleep(void *info);
62 static void lwkt_serialize_wakeup(void *info);
65 lwkt_serialize_init(lwkt_serialize_t s)
67 atomic_intr_init(&s->interlock);
69 s->last_td = (void *)-4;
74 lwkt_serialize_enter(lwkt_serialize_t s)
77 KKASSERT(s->last_td != curthread);
79 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
81 s->last_td = curthread;
86 lwkt_serialize_exit(lwkt_serialize_t s)
89 KKASSERT(s->last_td == curthread);
90 s->last_td = (void *)-2;
92 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
96 * Interrupt handler disablement support, used by drivers. Non-stackable
100 lwkt_serialize_handler_disable(lwkt_serialize_t s)
102 atomic_intr_handler_disable(&s->interlock);
106 lwkt_serialize_handler_enable(lwkt_serialize_t s)
108 atomic_intr_handler_enable(&s->interlock);
112 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *), void *arg)
115 * note: a return value of 0 indicates that the interrupt handler is
118 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) {
119 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s);
120 if (atomic_intr_handler_is_enabled(&s->interlock) == 0)
122 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s);
129 * It is possible to race an interrupt which acquires and releases the
130 * bit, then calls wakeup before we actually go to sleep, so we
131 * need to check that the interlock is still acquired from within
132 * a critical section prior to sleeping.
135 lwkt_serialize_sleep(void *info)
137 lwkt_serialize_t s = info;
139 if (atomic_intr_cond_test(&s->interlock) != 0)
140 tsleep(s, 0, "slize", 0);
145 lwkt_serialize_wakeup(void *info)