Import changeset

1 files changed, 132 insertions, 0 deletions

diff --git a/mit-pthreads/stdio/fwalk.c b/mit-pthreads/stdio/fwalk.c
new file mode 100644
index 00000000000..58a199e0707
--- /dev/null
+++ b/mit-pthreads/stdio/fwalk.c
@@ -0,0 +1,132 @@
+/*-
+ * Copyright (c) 1990 The Regents of the University of California.
+ * Copyright (c) 1993, 1994 Chris Provenzano. 
+ * 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 = "$Id$";
+#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 = n;
+							saveg = g;
+							savefp = fp;
+							continue;
+						}
+					} else {
+						ret |= __sflush(fp);
+						funlockfile(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)) {
+						flockfile(fp);
+						ret |= __sflush(fp);
+						funlockfile(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);
+}
+