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6008862bc2
most cases NULL is passed, but in some cases such as network driver locks (which use the MTX_NETWORK_LOCK macro) and UMA zone locks, a name is used. Tested on: i386, alpha, sparc64
178 lines
4.8 KiB
C
178 lines
4.8 KiB
C
/*
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* Copyright (C) 2001 Jason Evans <jasone@freebsd.org>. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice(s), this list of conditions and the following disclaimer as
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* the first lines of this file unmodified other than the possible
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* addition of one or more copyright notices.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice(s), this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGE.
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*
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* $FreeBSD$
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*/
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/*
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* Counting semaphores.
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*
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* Priority propagation will not generally raise the priority of semaphore
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* "owners" (a misnomer in the context of semaphores), so should not be relied
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* upon in combination with semaphores.
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*/
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#include <sys/param.h>
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#include <sys/systm.h>
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#include <sys/ktr.h>
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#include <sys/condvar.h>
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#include <sys/lock.h>
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#include <sys/mutex.h>
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#include <sys/sema.h>
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void
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sema_init(struct sema *sema, int value, const char *description)
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{
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KASSERT((value >= 0), ("%s(): negative value\n", __func__));
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bzero(sema, sizeof(*sema));
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mtx_init(&sema->sema_mtx, description, "sema backing lock",
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MTX_DEF | MTX_NOWITNESS | MTX_QUIET);
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cv_init(&sema->sema_cv, description);
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sema->sema_value = value;
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CTR4(KTR_LOCK, "%s(%p, %d, \"%s\")", __func__, sema, value, description);
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}
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void
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sema_destroy(struct sema *sema)
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{
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CTR3(KTR_LOCK, "%s(%p) \"%s\"", __func__, sema,
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cv_wmesg(&sema->sema_cv));
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KASSERT((sema->sema_waiters == 0), ("%s(): waiters\n", __func__));
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mtx_destroy(&sema->sema_mtx);
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cv_destroy(&sema->sema_cv);
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}
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void
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_sema_post(struct sema *sema, const char *file, int line)
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{
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mtx_lock(&sema->sema_mtx);
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sema->sema_value++;
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if (sema->sema_waiters && sema->sema_value > 0)
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cv_signal(&sema->sema_cv);
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CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema,
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cv_wmesg(&sema->sema_cv), sema->sema_value, file, line);
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mtx_unlock(&sema->sema_mtx);
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}
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void
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_sema_wait(struct sema *sema, const char *file, int line)
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{
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mtx_lock(&sema->sema_mtx);
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while (sema->sema_value == 0) {
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sema->sema_waiters++;
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cv_wait(&sema->sema_cv, &sema->sema_mtx);
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sema->sema_waiters--;
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}
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sema->sema_value--;
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CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema,
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cv_wmesg(&sema->sema_cv), sema->sema_value, file, line);
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mtx_unlock(&sema->sema_mtx);
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}
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int
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_sema_timedwait(struct sema *sema, int timo, const char *file, int line)
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{
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int ret, timed_out;
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mtx_lock(&sema->sema_mtx);
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/*
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* A spurious wakeup will cause the timeout interval to start over.
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* This isn't a big deal as long as spurious wakeups don't occur
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* continuously, since the timeout period is merely a lower bound on how
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* long to wait.
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*/
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for (timed_out = 0; sema->sema_value == 0 && timed_out == 0;) {
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sema->sema_waiters++;
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timed_out = cv_timedwait(&sema->sema_cv, &sema->sema_mtx, timo);
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sema->sema_waiters--;
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}
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if (sema->sema_value > 0) {
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/* Success. */
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sema->sema_value--;
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ret = 1;
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CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema,
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cv_wmesg(&sema->sema_cv), sema->sema_value, file, line);
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} else {
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ret = 0;
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CTR5(KTR_LOCK, "%s(%p) \"%s\" fail at %s:%d", __func__, sema,
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cv_wmesg(&sema->sema_cv), file, line);
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}
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mtx_unlock(&sema->sema_mtx);
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return (ret);
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}
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int
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_sema_trywait(struct sema *sema, const char *file, int line)
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{
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int ret;
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mtx_lock(&sema->sema_mtx);
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if (sema->sema_value > 0) {
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/* Success. */
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sema->sema_value--;
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ret = 1;
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CTR6(KTR_LOCK, "%s(%p) \"%s\" v = %d at %s:%d", __func__, sema,
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cv_wmesg(&sema->sema_cv), sema->sema_value, file, line);
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} else {
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ret = 0;
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CTR5(KTR_LOCK, "%s(%p) \"%s\" fail at %s:%d", __func__, sema,
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cv_wmesg(&sema->sema_cv), file, line);
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}
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mtx_unlock(&sema->sema_mtx);
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return (ret);
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}
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int
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sema_value(struct sema *sema)
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{
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int ret;
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mtx_lock(&sema->sema_mtx);
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ret = sema->sema_value;
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mtx_unlock(&sema->sema_mtx);
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return (ret);
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}
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