132 lines
4.7 KiB
C
132 lines
4.7 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Chris Torek.
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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, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, 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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER 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
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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/*static char *sccsid = "from: @(#)fwalk.c 5.2 (Berkeley) 2/24/91";*/
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static char *rcsid = "$Id: fwalk.c,v 1.1 1994/02/07 22:06:05 proven Exp $";
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#endif /* LIBC_SCCS and not lint */
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#include <pthread.h>
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#include <errno.h>
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#include <stdio.h>
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#include "local.h"
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#include "glue.h"
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extern pthread_mutex_t __sfp_mutex;
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extern pthread_cond_t __sfp_cond;
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extern int __sfp_state;
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/*
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* fwalk now can only be used for flushing the buffers.
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* This is all it was originally used for.
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* The function has also become much more complicated.
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* The first time through we flush everything we can.
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* If this fails to flush everything because we couldn't get a lock
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* we wait on the locksfor the second pass. Why this works ...
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*
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* This function must allow for multiple threads to flush everything.
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* This function cannot flush buffers locked by another thread.
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* So we flush everything we can the first pass. This includes all
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* buffers locked by this thread, and wait on buffers that are locked.
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* Eventually other threads willl unlock there buffers or flush them themselves
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* at which point this thread will notice that it's empty or be able to
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* flush the buffer. This is fine so long as no other thread tries to flush
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* all buffers. Here is the possible deadlock condition, but since this thread
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* has flushed all buffers it can, there are NO buffers locked by this thread
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* that need flushing so any other thread flushing won't block waiting on this
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* thread thereby eliminating the deadlock condition.
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*/
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int __swalk_sflush()
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{
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register FILE *fp, *savefp;
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register int n, ret, saven;
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register struct glue *g, *saveg;
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/* Only allow other threads to read __sglue */
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pthread_mutex_lock(&__sfp_mutex);
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__sfp_state++;
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pthread_mutex_unlock(&__sfp_mutex);
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ret = 0;
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saven = 0;
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saveg = NULL;
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savefp = NULL;
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for (g = &__sglue; g != NULL; g = g->next) {
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for (fp = g->iobs, n = g->niobs; --n >= 0; fp++) {
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if (fp->_flags != 0) {
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/* Is there anything to flush? */
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if (fp->_bf._base && (fp->_bf._base - fp->_p)) {
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if (ftrylockfile(fp)) { /* Can we flush it */
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if (!saven) { /* No, save first fp we can't flush */
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saven;
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saveg = g;
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savefp = fp;
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continue;
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}
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ret |= __sflush(fp);
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}
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}
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}
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}
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}
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if (savefp) {
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for (g = saveg; g != NULL; g = g->next) {
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for (fp = savefp, n = saven + 1; --n >= 0; fp++) {
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if (fp->_flags != 0) {
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/* Anything to flush */
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while (fp->_bf._base && (fp->_bf._base - fp->_p)) {
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if (ftrylockfile(fp)) { /* Can we flush it */
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pthread_yield();
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continue;
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}
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ret |= __sflush(fp);
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}
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}
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}
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}
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}
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/* If no other readers wakeup a thread waiting to do __sfp */
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pthread_mutex_lock(&__sfp_mutex);
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if (! (--__sfp_state)) {
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pthread_cond_signal(&__sfp_cond);
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}
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pthread_mutex_unlock(&__sfp_mutex);
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return (ret);
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}
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