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/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Chris Torek.
*
* 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, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
*/
#if defined(LIBC_SCCS) && !defined(lint)
/*static char *sccsid = "from: @(#)fwalk.c 5.2 (Berkeley) 2/24/91";*/
static char *rcsid = "$Id: fwalk.c,v 1.1 1995/10/18 08:43:07 deraadt Exp $";
#endif /* LIBC_SCCS and not lint */
#include <pthread.h>
#include <errno.h>
#include <stdio.h>
#include "local.h"
#include "glue.h"
extern pthread_mutex_t __sfp_mutex;
extern pthread_cond_t __sfp_cond;
extern int __sfp_state;
/*
* fwalk now can only be used for flushing the buffers.
* This is all it was originally used for.
* The function has also become much more complicated.
* The first time through we flush everything we can.
* If this fails to flush everything because we couldn't get a lock
* we wait on the locksfor the second pass. Why this works ...
*
* This function must allow for multiple threads to flush everything.
* This function cannot flush buffers locked by another thread.
* So we flush everything we can the first pass. This includes all
* buffers locked by this thread, and wait on buffers that are locked.
* Eventually other threads willl unlock there buffers or flush them themselves
* at which point this thread will notice that it's empty or be able to
* flush the buffer. This is fine so long as no other thread tries to flush
* all buffers. Here is the possible deadlock condition, but since this thread
* has flushed all buffers it can, there are NO buffers locked by this thread
* that need flushing so any other thread flushing won't block waiting on this
* thread thereby eliminating the deadlock condition.
*/
int __swalk_sflush()
{
register FILE *fp, *savefp;
register int n, ret, saven;
register struct glue *g, *saveg;
/* Only allow other threads to read __sglue */
pthread_mutex_lock(&__sfp_mutex);
__sfp_state++;
pthread_mutex_unlock(&__sfp_mutex);
ret = 0;
saven = 0;
saveg = NULL;
savefp = NULL;
for (g = &__sglue; g != NULL; g = g->next) {
for (fp = g->iobs, n = g->niobs; --n >= 0; fp++) {
if (fp->_flags != 0) {
/* Is there anything to flush? */
if (fp->_bf._base && (fp->_bf._base - fp->_p)) {
if (ftrylockfile(fp)) { /* Can we flush it */
if (!saven) { /* No, save first fp we can't flush */
saven;
saveg = g;
savefp = fp;
continue;
}
ret |= __sflush(fp);
}
}
}
}
}
if (savefp) {
for (g = saveg; g != NULL; g = g->next) {
for (fp = savefp, n = saven + 1; --n >= 0; fp++) {
if (fp->_flags != 0) {
/* Anything to flush */
while (fp->_bf._base && (fp->_bf._base - fp->_p)) {
if (ftrylockfile(fp)) { /* Can we flush it */
pthread_yield();
continue;
}
ret |= __sflush(fp);
}
}
}
}
}
/* If no other readers wakeup a thread waiting to do __sfp */
pthread_mutex_lock(&__sfp_mutex);
if (! (--__sfp_state)) {
pthread_cond_signal(&__sfp_cond);
}
pthread_mutex_unlock(&__sfp_mutex);
return (ret);
}
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