1285SN/A/*- 2462SN/A * SPDX-License-Identifier: BSD-2-Clause 3285SN/A * 4285SN/A * Copyright (C) 2001 Jason Evans <jasone@freebsd.org>. All rights reserved. 5285SN/A * 6285SN/A * Redistribution and use in source and binary forms, with or without 7285SN/A * modification, are permitted provided that the following conditions 8285SN/A * are met: 9285SN/A * 1. Redistributions of source code must retain the above copyright 10285SN/A * notice(s), this list of conditions and the following disclaimer as 11285SN/A * the first lines of this file unmodified other than the possible 12285SN/A * addition of one or more copyright notices. 13285SN/A * 2. Redistributions in binary form must reproduce the above copyright 14285SN/A * notice(s), this list of conditions and the following disclaimer in the 15285SN/A * documentation and/or other materials provided with the distribution. 16285SN/A * 17285SN/A * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY 18285SN/A * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19285SN/A * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20285SN/A * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY 21285SN/A * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22285SN/A * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 23285SN/A * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 24285SN/A * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25285SN/A * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26285SN/A * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH 27285SN/A * DAMAGE. 28285SN/A */ 29285SN/A 30285SN/A/* 31285SN/A * Counting semaphores. 32285SN/A * 33285SN/A * Priority propagation will not generally raise the priority of semaphore 34285SN/A * "owners" (a misnomer in the context of semaphores), so should not be relied 35285SN/A * upon in combination with semaphores. 36285SN/A */ 37285SN/A 38285SN/A#include <sys/param.h> 39285SN/A#include <sys/systm.h> 40285SN/A#include <sys/ktr.h> 41285SN/A#include <sys/condvar.h> 42285SN/A#include <sys/lock.h> 43285SN/A#include <sys/mutex.h> 44285SN/A#include <sys/sema.h> 45285SN/A 46285SN/Avoid 47285SN/Asema_init(struct sema *sema, int value, const char *description) 48285SN/A{ 49285SN/A 50285SN/A KASSERT((value >= 0), ("%s(): negative value\n", __func__)); 51285SN/A 52285SN/A bzero(sema, sizeof(*sema)); 53285SN/A mtx_init(&sema->sema_mtx, description, "sema backing lock", 54285SN/A MTX_DEF | MTX_NOWITNESS | MTX_QUIET); 55285SN/A cv_init(&sema->sema_cv, description); 56285SN/A sema->sema_value = value; 57285SN/A 58285SN/A CTR4(KTR_LOCK, "%s(%p, %d, \"%s\")", __func__, sema, value, description); 59285SN/A} 60285SN/A 61285SN/Avoid 62285SN/Asema_destroy(struct sema *sema) 63285SN/A{ 64285SN/A 65285SN/A CTR3(KTR_LOCK, "%s(%p) \"%s\"", __func__, sema, 66285SN/A cv_wmesg(&sema->sema_cv)); 67285SN/A 68285SN/A KASSERT((sema->sema_waiters == 0), ("%s(): waiters\n", __func__)); 69285SN/A 70285SN/A mtx_destroy(&sema->sema_mtx); 71285SN/A cv_destroy(&sema->sema_cv); 72285SN/A} 73285SN/A 74285SN/Avoid 75285SN/A_sema_post(struct sema *sema, const char *file, int line) 76285SN/A{ 77285SN/A 78285SN/A mtx_lock(&sema->sema_mtx); 79285SN/A sema->sema_value++; 80285SN/A if (sema->sema_waiters && sema->sema_value > 0) 81285SN/A cv_signal(&sema->sema_cv); 82285SN/A 83285SN/A CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, 84285SN/A cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); 85285SN/A 86285SN/A mtx_unlock(&sema->sema_mtx); 87285SN/A} 88285SN/A 89285SN/Avoid 90285SN/A_sema_wait(struct sema *sema, const char *file, int line) 91285SN/A{ 92285SN/A 93285SN/A mtx_lock(&sema->sema_mtx); 94285SN/A while (sema->sema_value == 0) { 95285SN/A sema->sema_waiters++; 96285SN/A cv_wait(&sema->sema_cv, &sema->sema_mtx); 97285SN/A sema->sema_waiters--; 98285SN/A } 99285SN/A sema->sema_value--; 100285SN/A 101285SN/A CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, 102285SN/A cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); 103285SN/A 104285SN/A mtx_unlock(&sema->sema_mtx); 105285SN/A} 106285SN/A 107285SN/Aint 108285SN/A_sema_timedwait(struct sema *sema, int timo, const char *file, int line) 109285SN/A{ 110285SN/A int error; 111285SN/A 112285SN/A mtx_lock(&sema->sema_mtx); 113285SN/A 114285SN/A /* 115285SN/A * A spurious wakeup will cause the timeout interval to start over. 116285SN/A * This isn't a big deal as long as spurious wakeups don't occur 117285SN/A * continuously, since the timeout period is merely a lower bound on how 118285SN/A * long to wait. 119285SN/A */ 120285SN/A for (error = 0; sema->sema_value == 0 && error == 0;) { 121285SN/A sema->sema_waiters++; 122285SN/A error = cv_timedwait(&sema->sema_cv, &sema->sema_mtx, timo); 123285SN/A sema->sema_waiters--; 124285SN/A } 125285SN/A if (sema->sema_value > 0) { 126285SN/A /* Success. */ 127285SN/A sema->sema_value--; 128285SN/A error = 0; 129285SN/A 130285SN/A CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, 131285SN/A cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); 132285SN/A } else { 133285SN/A CTR5(KTR_LOCK, "%s(%p) \"%s\" fail at %s:%d", __func__, sema, 134285SN/A cv_wmesg(&sema->sema_cv), file, line); 135285SN/A } 136285SN/A 137285SN/A mtx_unlock(&sema->sema_mtx); 138285SN/A return (error); 139285SN/A} 140285SN/A 141285SN/Aint 142285SN/A_sema_trywait(struct sema *sema, const char *file, int line) 143367SN/A{ 144367SN/A int ret; 145367SN/A 146367SN/A mtx_lock(&sema->sema_mtx); 147367SN/A 148367SN/A if (sema->sema_value > 0) { 149367SN/A /* Success. */ 150367SN/A sema->sema_value--; 151367SN/A ret = 1; 152367SN/A 153367SN/A CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, 154285SN/A cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); 155285SN/A } else { 156367SN/A ret = 0; 157285SN/A 158285SN/A CTR5(KTR_LOCK, "%s(%p) \"%s\" fail at %s:%d", __func__, sema, 159285SN/A cv_wmesg(&sema->sema_cv), file, line); 160285SN/A } 161285SN/A 162285SN/A mtx_unlock(&sema->sema_mtx); 163285SN/A return (ret); 164285SN/A} 165367SN/A 166367SN/Aint 167367SN/Asema_value(struct sema *sema) 168367SN/A{ 169367SN/A int ret; 170367SN/A 171367SN/A mtx_lock(&sema->sema_mtx); 172367SN/A ret = sema->sema_value; 173367SN/A mtx_unlock(&sema->sema_mtx); 174367SN/A return (ret); 175367SN/A} 176367SN/A