Fix the handle locking in stdio to use flockfile/funlockfile

internally when and where required.  Macros in <stdio.h> are updated
to automatically call the underlying functions when the process is
threaded to obtain the necessary locking.  A private mutex is added
to protect __sglue, the internal list of FILE handles, and another
to protect the one-time initialization.  Some routines in libc that
use getc() change to use getc_unlocked() as they're either protected
by their own lock or aren't thread-safe routines anyway.

ok kurt@, earlier version tested by sthen@ and jj@

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/libc/stdio/refill.c b/lib/libc/stdio/refill.c
index 74b378e1488..a559ca9b320 100644
--- a/lib/libc/stdio/refill.c
+++ b/lib/libc/stdio/refill.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: refill.c,v 1.8 2005/08/08 08:05:36 espie Exp $ */
+/*	$OpenBSD: refill.c,v 1.9 2009/10/21 16:04:23 guenther Exp $ */
 /*-
  * Copyright (c) 1990, 1993
  *	The Regents of the University of California.  All rights reserved.
@@ -39,9 +39,8 @@
 static int
 lflush(FILE *fp)
 {
-
 	if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
-		return (__sflush(fp));
+		return (__sflush_locked(fp));	/* ignored... */
 	return (0);
 }
 
@@ -103,8 +102,16 @@ __srefill(FILE *fp)
 	 * flush all line buffered output files, per the ANSI C
 	 * standard.
 	 */
-	if (fp->_flags & (__SLBF|__SNBF))
+	if (fp->_flags & (__SLBF|__SNBF)) {
+		/* Ignore this file in _fwalk to avoid potential deadlock. */
+		fp->_flags |= __SIGN;
 		(void) _fwalk(lflush);
+		fp->_flags &= ~__SIGN;
+
+		/* Now flush this file without locking it. */
+		if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
+			__sflush(fp);
+	}
 	fp->_p = fp->_bf._base;
 	fp->_r = (*fp->_read)(fp->_cookie, (char *)fp->_p, fp->_bf._size);
 	fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */