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 * $DragonFly: src/sys/kern/lwkt_serialize.c,v 1.6 2005/10/13 00:02:22 dillon Exp $ 35 */ 36 /* 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. 40 * 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. 45 */ 46 47 #include <sys/param.h> 48 #include <sys/systm.h> 49 #include <sys/kernel.h> 50 #include <sys/proc.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> 58 #include <sys/lock.h> 59 #include <sys/caps.h> 60 61 static void lwkt_serialize_sleep(void *info); 62 static void lwkt_serialize_wakeup(void *info); 63 64 void 65 lwkt_serialize_init(lwkt_serialize_t s) 66 { 67 atomic_intr_init(&s->interlock); 68 #ifdef INVARIANTS 69 s->last_td = (void *)-4; 70 #endif 71 } 72 73 void 74 lwkt_serialize_enter(lwkt_serialize_t s) 75 { 76 #ifdef INVARIANTS 77 KKASSERT(s->last_td != curthread); 78 #endif 79 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 80 #ifdef INVARIANTS 81 s->last_td = curthread; 82 #endif 83 } 84 85 void 86 lwkt_serialize_exit(lwkt_serialize_t s) 87 { 88 #ifdef INVARIANTS 89 KKASSERT(s->last_td == curthread); 90 s->last_td = (void *)-2; 91 #endif 92 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 93 } 94 95 /* 96 * Interrupt handler disablement support, used by drivers. Non-stackable 97 * (uses bit 30). 98 */ 99 void 100 lwkt_serialize_handler_disable(lwkt_serialize_t s) 101 { 102 atomic_intr_handler_disable(&s->interlock); 103 } 104 105 void 106 lwkt_serialize_handler_enable(lwkt_serialize_t s) 107 { 108 atomic_intr_handler_enable(&s->interlock); 109 } 110 111 void 112 lwkt_serialize_handler_call(lwkt_serialize_t s, void (*func)(void *, void *), 113 void *arg, void *frame) 114 { 115 /* 116 * note: a return value of 0 indicates that the interrupt handler is 117 * enabled. 118 */ 119 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 120 atomic_intr_cond_enter(&s->interlock, lwkt_serialize_sleep, s); 121 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) 122 func(arg, frame); 123 atomic_intr_cond_exit(&s->interlock, lwkt_serialize_wakeup, s); 124 } 125 } 126 127 /* 128 * Similar to handler_call but does not block. Returns 0 on success, 129 * and 1 on failure. 130 */ 131 int 132 lwkt_serialize_handler_try(lwkt_serialize_t s, void (*func)(void *, void *), 133 void *arg, void *frame) 134 { 135 /* 136 * note: a return value of 0 indicates that the interrupt handler is 137 * enabled. 138 */ 139 if (atomic_intr_handler_is_enabled(&s->interlock) == 0) { 140 if (atomic_intr_cond_try(&s->interlock) == 0) { 141 func(arg, frame); 142 return(0); 143 } 144 } 145 return(1); 146 } 147 148 149 /* 150 * Helper functions 151 * 152 * It is possible to race an interrupt which acquires and releases the 153 * bit, then calls wakeup before we actually go to sleep, so we 154 * need to check that the interlock is still acquired from within 155 * a critical section prior to sleeping. 156 */ 157 static void 158 lwkt_serialize_sleep(void *info) 159 { 160 lwkt_serialize_t s = info; 161 crit_enter(); 162 if (atomic_intr_cond_test(&s->interlock) != 0) 163 tsleep(s, 0, "slize", 0); 164 crit_exit(); 165 } 166 167 static void 168 lwkt_serialize_wakeup(void *info) 169 { 170 wakeup(info); 171 } 172 173