Current Path : /sys/kern/ |
FreeBSD hs32.drive.ne.jp 9.1-RELEASE FreeBSD 9.1-RELEASE #1: Wed Jan 14 12:18:08 JST 2015 root@hs32.drive.ne.jp:/sys/amd64/compile/hs32 amd64 |
Current File : //sys/kern/kern_sema.c |
/*- * Copyright (C) 2001 Jason Evans <jasone@freebsd.org>. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice(s), this list of conditions and the following disclaimer as * the first lines of this file unmodified other than the possible * addition of one or more copyright notices. * 2. Redistributions in binary form must reproduce the above copyright * notice(s), this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH * DAMAGE. */ /* * Counting semaphores. * * Priority propagation will not generally raise the priority of semaphore * "owners" (a misnomer in the context of semaphores), so should not be relied * upon in combination with semaphores. */ #include <sys/cdefs.h> __FBSDID("$FreeBSD: release/9.1.0/sys/kern/kern_sema.c 139804 2005-01-06 23:35:40Z imp $"); #include <sys/param.h> #include <sys/systm.h> #include <sys/ktr.h> #include <sys/condvar.h> #include <sys/lock.h> #include <sys/mutex.h> #include <sys/sema.h> void sema_init(struct sema *sema, int value, const char *description) { KASSERT((value >= 0), ("%s(): negative value\n", __func__)); bzero(sema, sizeof(*sema)); mtx_init(&sema->sema_mtx, description, "sema backing lock", MTX_DEF | MTX_NOWITNESS | MTX_QUIET); cv_init(&sema->sema_cv, description); sema->sema_value = value; CTR4(KTR_LOCK, "%s(%p, %d, \"%s\")", __func__, sema, value, description); } void sema_destroy(struct sema *sema) { CTR3(KTR_LOCK, "%s(%p) \"%s\"", __func__, sema, cv_wmesg(&sema->sema_cv)); KASSERT((sema->sema_waiters == 0), ("%s(): waiters\n", __func__)); mtx_destroy(&sema->sema_mtx); cv_destroy(&sema->sema_cv); } void _sema_post(struct sema *sema, const char *file, int line) { mtx_lock(&sema->sema_mtx); sema->sema_value++; if (sema->sema_waiters && sema->sema_value > 0) cv_signal(&sema->sema_cv); CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); mtx_unlock(&sema->sema_mtx); } void _sema_wait(struct sema *sema, const char *file, int line) { mtx_lock(&sema->sema_mtx); while (sema->sema_value == 0) { sema->sema_waiters++; cv_wait(&sema->sema_cv, &sema->sema_mtx); sema->sema_waiters--; } sema->sema_value--; CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); mtx_unlock(&sema->sema_mtx); } int _sema_timedwait(struct sema *sema, int timo, const char *file, int line) { int error; mtx_lock(&sema->sema_mtx); /* * A spurious wakeup will cause the timeout interval to start over. * This isn't a big deal as long as spurious wakeups don't occur * continuously, since the timeout period is merely a lower bound on how * long to wait. */ for (error = 0; sema->sema_value == 0 && error == 0;) { sema->sema_waiters++; error = cv_timedwait(&sema->sema_cv, &sema->sema_mtx, timo); sema->sema_waiters--; } if (sema->sema_value > 0) { /* Success. */ sema->sema_value--; error = 0; CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); } else { CTR5(KTR_LOCK, "%s(%p) \"%s\" fail at %s:%d", __func__, sema, cv_wmesg(&sema->sema_cv), file, line); } mtx_unlock(&sema->sema_mtx); return (error); } int _sema_trywait(struct sema *sema, const char *file, int line) { int ret; mtx_lock(&sema->sema_mtx); if (sema->sema_value > 0) { /* Success. */ sema->sema_value--; ret = 1; CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema, cv_wmesg(&sema->sema_cv), sema->sema_value, file, line); } else { ret = 0; CTR5(KTR_LOCK, "%s(%p) \"%s\" fail at %s:%d", __func__, sema, cv_wmesg(&sema->sema_cv), file, line); } mtx_unlock(&sema->sema_mtx); return (ret); } int sema_value(struct sema *sema) { int ret; mtx_lock(&sema->sema_mtx); ret = sema->sema_value; mtx_unlock(&sema->sema_mtx); return (ret); }