* libc/stdio/fclose.c: Only use sfp lock to guard non-atomic

	changes of flags and fp lock.
	* libc/stdio/freopen.c: Ditto.
	* libc/stdio/freopen64.c: Ditto.
	* libc/stdio/fgetc.c: Revert change from 2009-04-24, remove sfp locks
	which guard entire function to avoid potential deadlocks when using
	stdio functions in multiple thraeds.
	* libc/stdio/fgets.c: Ditto.
	* libc/stdio/fgetwc.c: Ditto.
	* libc/stdio/fgetws.c: Ditto.
	* libc/stdio/fread.c: Ditto.
	* libc/stdio/fseek.c: Ditto.
	* libc/stdio/getc.c: Ditto.
	* libc/stdio/getdelim.c: Ditto.
	* libc/stdio/gets.c: Ditto.
	* libc/stdio/vfscanf.c: Ditto.
	* libc/stdio/vfwscanf.c: Ditto.

	* libc/stdio/fflush.c (_fflush_r): Split out core functionality into
	new function __sflush_r.  Just lock file and call __sflush_r from here.
	* libc/stdio/fwalk.c (_fwalk): Remove static helper function and move
	functionality back into main function. Don't walk a file with flags
	value of 1.  Add comment.
	(_fwalk_reent): Ditto.
	* libc/stdio/local.h (__sflush_r): Declare.
	* libc/stdio/refill.c (__srefill): Before calling fwalk, set flags
	value to 1 so this file pointer isn't walked.  Revert flags afterwards
	and call __sflush_r for this fp if necessary.  Add comments.

19 files changed, 106 insertions, 132 deletions

diff --git a/newlib/ChangeLog b/newlib/ChangeLog
index 5fff8ad..d1da383 100644
--- a/newlib/ChangeLog
+++ b/newlib/ChangeLog
@@ -1,3 +1,34 @@
+2011-01-28  Corinna Vinschen  <vinschen@redhat.com>
+
+	* libc/stdio/fclose.c: Only use sfp lock to guard non-atomic
+	changes of flags and fp lock.
+	* libc/stdio/freopen.c: Ditto.
+	* libc/stdio/freopen64.c: Ditto.
+	* libc/stdio/fgetc.c: Revert change from 2009-04-24, remove sfp locks
+	which guard entire function to avoid potential deadlocks when using
+	stdio functions in multiple thraeds.
+	* libc/stdio/fgets.c: Ditto.
+	* libc/stdio/fgetwc.c: Ditto.
+	* libc/stdio/fgetws.c: Ditto.
+	* libc/stdio/fread.c: Ditto.
+	* libc/stdio/fseek.c: Ditto.
+	* libc/stdio/getc.c: Ditto.
+	* libc/stdio/getdelim.c: Ditto.
+	* libc/stdio/gets.c: Ditto.
+	* libc/stdio/vfscanf.c: Ditto.
+	* libc/stdio/vfwscanf.c: Ditto.
+
+	* libc/stdio/fflush.c (_fflush_r): Split out core functionality into
+	new function __sflush_r.  Just lock file and call __sflush_r from here.
+	* libc/stdio/fwalk.c (_fwalk): Remove static helper function and move
+	functionality back into main function. Don't walk a file with flags
+	value of 1.  Add comment.
+	(_fwalk_reent): Ditto.
+	* libc/stdio/local.h (__sflush_r): Declare.
+	* libc/stdio/refill.c (__srefill): Before calling fwalk, set flags
+	value to 1 so this file pointer isn't walked.  Revert flags afterwards
+	and call __sflush_r for this fp if necessary.  Add comments.
+
 2011-01-27  Corinna Vinschen  <vinschen@redhat.com>
 
 	* libc/include/sys/features.h: Define __STDC_ISO_10646__ for Cygwin.
diff --git a/newlib/libc/stdio/fclose.c b/newlib/libc/stdio/fclose.c
index a14a63f..3c8868a 100644
--- a/newlib/libc/stdio/fclose.c
+++ b/newlib/libc/stdio/fclose.c
@@ -74,8 +74,6 @@ _DEFUN(_fclose_r, (rptr, fp),
   if (fp == NULL)
     return (0);			/* on NULL */
 
-  __sfp_lock_acquire ();
-
   CHECK_INIT (rptr, fp);
 
   _flockfile (fp);
@@ -83,7 +81,6 @@ _DEFUN(_fclose_r, (rptr, fp),
   if (fp->_flags == 0)		/* not open! */
     {
       _funlockfile (fp);
-      __sfp_lock_release ();
       return (0);
     }
   /* Unconditionally flush to allow special handling for seekable read
@@ -98,6 +95,7 @@ _DEFUN(_fclose_r, (rptr, fp),
     FREEUB (rptr, fp);
   if (HASLB (fp))
     FREELB (rptr, fp);
+  __sfp_lock_acquire ();
   fp->_flags = 0;		/* release this FILE for reuse */
   _funlockfile (fp);
 #ifndef __SINGLE_THREAD__
diff --git a/newlib/libc/stdio/fflush.c b/newlib/libc/stdio/fflush.c
index ea6d2fb..130c148 100644
--- a/newlib/libc/stdio/fflush.c
+++ b/newlib/libc/stdio/fflush.c
@@ -67,37 +67,16 @@ No supporting OS subroutines are required.
 
 /* Flush a single file, or (if fp is NULL) all files.  */
 
+/* Core function which does not lock file pointer.  This gets called
+   directly from __srefill. */
 int
-_DEFUN(_fflush_r, (ptr, fp),
+_DEFUN(__sflush_r, (ptr, fp),
        struct _reent *ptr _AND
        register FILE * fp)
 {
   register unsigned char *p;
   register int n, t;
 
-#ifdef _REENT_SMALL
-  /* For REENT_SMALL platforms, it is possible we are being
-     called for the first time on a std stream.  This std
-     stream can belong to a reentrant struct that is not
-     _REENT.  If CHECK_INIT gets called below based on _REENT,
-     we will end up changing said file pointers to the equivalent
-     std stream off of _REENT.  This causes unexpected behavior if
-     there is any data to flush on the _REENT std stream.  There
-     are two alternatives to fix this:  1) make a reentrant fflush
-     or 2) simply recognize that this file has nothing to flush
-     and return immediately before performing a CHECK_INIT.  Choice
-     2 is implemented here due to its simplicity.  */
-  if (fp->_bf._base == NULL)
-    return 0;
-#endif /* _REENT_SMALL  */
-
-  CHECK_INIT (ptr, fp);
-
-  if (!fp->_flags)
-    return 0;
-
-  _flockfile (fp);
-
   t = fp->_flags;
   if ((t & __SWR) == 0)
     {
@@ -150,7 +129,6 @@ _DEFUN(_fflush_r, (ptr, fp),
 		    }
 		  else
 		    fp->_flags |= __SERR;
-		  _funlockfile (fp);
 		  return result;
 		}
             }
@@ -186,17 +164,14 @@ _DEFUN(_fflush_r, (ptr, fp),
 	  else
 	    {
 	      fp->_flags |= __SERR;
-	      _funlockfile (fp);
 	      return EOF;
 	    }
 	}
-      _funlockfile (fp);
       return 0;
     }
   if ((p = fp->_bf._base) == NULL)
     {
       /* Nothing to flush.  */
-      _funlockfile (fp);
       return 0;
     }
   n = fp->_p - p;		/* write this much */
@@ -215,16 +190,48 @@ _DEFUN(_fflush_r, (ptr, fp),
       if (t <= 0)
 	{
           fp->_flags |= __SERR;
-          _funlockfile (fp);
           return EOF;
 	}
       p += t;
       n -= t;
     }
-  _funlockfile (fp);
   return 0;
 }
 
+int
+_DEFUN(_fflush_r, (ptr, fp),
+       struct _reent *ptr _AND
+       register FILE * fp)
+{
+  int ret;
+
+#ifdef _REENT_SMALL
+  /* For REENT_SMALL platforms, it is possible we are being
+     called for the first time on a std stream.  This std
+     stream can belong to a reentrant struct that is not
+     _REENT.  If CHECK_INIT gets called below based on _REENT,
+     we will end up changing said file pointers to the equivalent
+     std stream off of _REENT.  This causes unexpected behavior if
+     there is any data to flush on the _REENT std stream.  There
+     are two alternatives to fix this:  1) make a reentrant fflush
+     or 2) simply recognize that this file has nothing to flush
+     and return immediately before performing a CHECK_INIT.  Choice
+     2 is implemented here due to its simplicity.  */
+  if (fp->_bf._base == NULL)
+    return 0;
+#endif /* _REENT_SMALL  */
+
+  CHECK_INIT (ptr, fp);
+
+  if (!fp->_flags)
+    return 0;
+
+  _flockfile (fp);
+  ret = __sflush_r (ptr, fp);
+  _funlockfile (fp);
+  return ret;
+}
+
 #ifndef _REENT_ONLY
 
 int
diff --git a/newlib/libc/stdio/fgetc.c b/newlib/libc/stdio/fgetc.c
index 9837a2e..e275cfe 100644
--- a/newlib/libc/stdio/fgetc.c
+++ b/newlib/libc/stdio/fgetc.c
@@ -93,11 +93,9 @@ _DEFUN(fgetc, (fp),
 #if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
   int result;
   CHECK_INIT(_REENT, fp);
-  __sfp_lock_acquire ();
   _flockfile (fp);
   result = __sgetc_r (_REENT, fp);
   _funlockfile (fp);
-  __sfp_lock_release ();
   return result;
 #else
   return _fgetc_r (_REENT, fp);
diff --git a/newlib/libc/stdio/fgets.c b/newlib/libc/stdio/fgets.c
index 21bfdd4..7f02e3f 100644
--- a/newlib/libc/stdio/fgets.c
+++ b/newlib/libc/stdio/fgets.c
@@ -98,7 +98,6 @@ _DEFUN(_fgets_r, (ptr, buf, n, fp),
 
   CHECK_INIT(ptr, fp);
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
 #ifdef __SCLE
   if (fp->_flags & __SCLE)
@@ -114,12 +113,10 @@ _DEFUN(_fgets_r, (ptr, buf, n, fp),
       if (c == EOF && s == buf)
         {
           _funlockfile (fp);
-	  __sfp_lock_release ();
           return NULL;
         }
       *s = 0;
       _funlockfile (fp);
-      __sfp_lock_release ();
       return buf;
     }
 #endif
@@ -138,7 +135,6 @@ _DEFUN(_fgets_r, (ptr, buf, n, fp),
 	      if (s == buf)
                 {
                   _funlockfile (fp);
-		  __sfp_lock_release ();
                   return 0;
                 }
 	      break;
@@ -164,7 +160,6 @@ _DEFUN(_fgets_r, (ptr, buf, n, fp),
 	  _CAST_VOID memcpy ((_PTR) s, (_PTR) p, len);
 	  s[len] = 0;
           _funlockfile (fp);
-	  __sfp_lock_release ();
 	  return (buf);
 	}
       fp->_r -= len;
@@ -175,7 +170,6 @@ _DEFUN(_fgets_r, (ptr, buf, n, fp),
   while ((n -= len) != 0);
   *s = 0;
   _funlockfile (fp);
-  __sfp_lock_release ();
   return buf;
 }
 
diff --git a/newlib/libc/stdio/fgetwc.c b/newlib/libc/stdio/fgetwc.c
index f4c81dd..38a79bc 100644
--- a/newlib/libc/stdio/fgetwc.c
+++ b/newlib/libc/stdio/fgetwc.c
@@ -164,12 +164,10 @@ _DEFUN(_fgetwc_r, (ptr, fp),
 {
   wint_t r;
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
   ORIENT(fp, 1);
   r = __fgetwc (ptr, fp);
   _funlockfile (fp);
-  __sfp_lock_release ();
   return r;
 }
 
diff --git a/newlib/libc/stdio/fgetws.c b/newlib/libc/stdio/fgetws.c
index 3dbae06..2784f15 100644
--- a/newlib/libc/stdio/fgetws.c
+++ b/newlib/libc/stdio/fgetws.c
@@ -93,7 +93,6 @@ _DEFUN(_fgetws_r, (ptr, ws, n, fp),
   const char *src;
   unsigned char *nl;
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
   ORIENT (fp, 1);
 
@@ -144,12 +143,10 @@ _DEFUN(_fgetws_r, (ptr, ws, n, fp),
     goto error;
   *wsp++ = L'\0';
   _funlockfile (fp);
-  __sfp_lock_release ();
   return ws;
 
 error:
   _funlockfile (fp);
-  __sfp_lock_release ();
   return NULL;
 }
 
diff --git a/newlib/libc/stdio/fread.c b/newlib/libc/stdio/fread.c
index dda2044..a39e9d8 100644
--- a/newlib/libc/stdio/fread.c
+++ b/newlib/libc/stdio/fread.c
@@ -146,7 +146,6 @@ _DEFUN(_fread_r, (ptr, buf, size, count, fp),
 
   CHECK_INIT(ptr, fp);
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
   ORIENT (fp, -1);
   if (fp->_r < 0)
@@ -197,12 +196,10 @@ _DEFUN(_fread_r, (ptr, buf, size, count, fp),
               if (fp->_flags & __SCLE)
 	        {
 	          _funlockfile (fp);
-		  __sfp_lock_release ();
 	          return crlf_r (ptr, fp, buf, total-resid, 1) / size;
 	        }
 #endif
 	      _funlockfile (fp);
-	      __sfp_lock_release ();
 	      return (total - resid) / size;
 	    }
 	}
@@ -224,12 +221,10 @@ _DEFUN(_fread_r, (ptr, buf, size, count, fp),
 	      if (fp->_flags & __SCLE)
 		{
 		  _funlockfile (fp);
-		  __sfp_lock_release ();
 		  return crlf_r (ptr, fp, buf, total-resid, 1) / size;
 		}
 #endif
 	      _funlockfile (fp);
-	      __sfp_lock_release ();
 	      return (total - resid) / size;
 	    }
 	}
@@ -243,12 +238,10 @@ _DEFUN(_fread_r, (ptr, buf, size, count, fp),
   if (fp->_flags & __SCLE)
     {
       _funlockfile (fp);
-      __sfp_lock_release ();
       return crlf_r(ptr, fp, buf, total, 0) / size;
     }
 #endif
   _funlockfile (fp);
-  __sfp_lock_release ();
   return count;
 }
 
diff --git a/newlib/libc/stdio/freopen.c b/newlib/libc/stdio/freopen.c
index ae774c6..1720062 100644
--- a/newlib/libc/stdio/freopen.c
+++ b/newlib/libc/stdio/freopen.c
@@ -98,8 +98,6 @@ _DEFUN(_freopen_r, (ptr, file, mode, fp),
   int flags, oflags;
   int e = 0;
 
-  __sfp_lock_acquire ();
-
   CHECK_INIT (ptr, fp);
 
   _flockfile (fp);
@@ -108,7 +106,6 @@ _DEFUN(_freopen_r, (ptr, file, mode, fp),
     {
       _funlockfile (fp);
       _fclose_r (ptr, fp);
-      __sfp_lock_release ();
       return NULL;
     }
 
@@ -208,6 +205,7 @@ _DEFUN(_freopen_r, (ptr, file, mode, fp),
 
   if (f < 0)
     {				/* did not get it after all */
+      __sfp_lock_acquire ();
       fp->_flags = 0;		/* set it free */
       ptr->_errno = e;		/* restore in case _close clobbered */
       _funlockfile (fp);
@@ -232,7 +230,6 @@ _DEFUN(_freopen_r, (ptr, file, mode, fp),
 #endif
 
   _funlockfile (fp);
-  __sfp_lock_release ();
   return fp;
 }
 
diff --git a/newlib/libc/stdio/fseek.c b/newlib/libc/stdio/fseek.c
index 0ba7b6c..c78d2b2 100644
--- a/newlib/libc/stdio/fseek.c
+++ b/newlib/libc/stdio/fseek.c
@@ -138,7 +138,6 @@ _DEFUN(_fseek_r, (ptr, fp, offset, whence),
 
   CHECK_INIT (ptr, fp);
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
 
   /* If we've been doing some writing, and we're in append mode
@@ -156,7 +155,6 @@ _DEFUN(_fseek_r, (ptr, fp, offset, whence),
     {
       ptr->_errno = ESPIPE;	/* ??? */
       _funlockfile (fp);
-      __sfp_lock_release ();
       return EOF;
     }
 
@@ -182,7 +180,6 @@ _DEFUN(_fseek_r, (ptr, fp, offset, whence),
 	  if (curoff == -1L)
 	    {
 	      _funlockfile (fp);
-	      __sfp_lock_release ();
 	      return EOF;
 	    }
 	}
@@ -208,7 +205,6 @@ _DEFUN(_fseek_r, (ptr, fp, offset, whence),
     default:
       ptr->_errno = EINVAL;
       _funlockfile (fp);
-      __sfp_lock_release ();
       return (EOF);
     }
 
@@ -268,7 +264,6 @@ _DEFUN(_fseek_r, (ptr, fp, offset, whence),
     {
       ptr->_errno = EOVERFLOW;
       _funlockfile (fp);
-      __sfp_lock_release ();
       return EOF;
     }
 
@@ -325,7 +320,6 @@ _DEFUN(_fseek_r, (ptr, fp, offset, whence),
       fp->_flags &= ~__SEOF;
       memset (&fp->_mbstate, 0, sizeof (_mbstate_t));
       _funlockfile (fp);
-      __sfp_lock_release ();
       return 0;
     }
 
@@ -356,7 +350,6 @@ _DEFUN(_fseek_r, (ptr, fp, offset, whence),
     }
   memset (&fp->_mbstate, 0, sizeof (_mbstate_t));
   _funlockfile (fp);
-  __sfp_lock_release ();
   return 0;
 
   /*
@@ -369,7 +362,6 @@ dumb:
       || seekfn (ptr, fp->_cookie, offset, whence) == POS_ERR)
     {
       _funlockfile (fp);
-      __sfp_lock_release ();
       return EOF;
     }
   /* success: clear EOF indicator and discard ungetc() data */
@@ -388,7 +380,6 @@ dumb:
   fp->_flags &= ~__SNPT;
   memset (&fp->_mbstate, 0, sizeof (_mbstate_t));
   _funlockfile (fp);
-  __sfp_lock_release ();
   return 0;
 }
 
diff --git a/newlib/libc/stdio/fwalk.c b/newlib/libc/stdio/fwalk.c
index 24cbe9a..df92d1d 100644
--- a/newlib/libc/stdio/fwalk.c
+++ b/newlib/libc/stdio/fwalk.c
@@ -27,8 +27,8 @@ static char sccsid[] = "%W% (Berkeley) %G%";
 #include <errno.h>
 #include "local.h"
 
-static int
-_DEFUN(__fwalk, (ptr, function),
+int
+_DEFUN(_fwalk, (ptr, function),
        struct _reent *ptr _AND
        register int (*function) (FILE *))
 {
@@ -36,11 +36,19 @@ _DEFUN(__fwalk, (ptr, function),
   register int n, ret = 0;
   register struct _glue *g;
 
+  /*
+   * It should be safe to walk the list without locking it;
+   * new nodes are only added to the end and none are ever
+   * removed.
+   *
+   * Avoid locking this list while walking it or else you will
+   * introduce a potential deadlock in [at least] refill.c.
+   */
   for (g = &ptr->__sglue; g != NULL; g = g->_next)
     for (fp = g->_iobs, n = g->_niobs; --n >= 0; fp++)
       if (fp->_flags != 0)
         {
-          if (fp->_flags != 0 && fp->_file != -1)
+          if (fp->_flags != 0 && fp->_flags != 1 && fp->_file != -1)
             ret |= (*function) (fp);
         }
 
@@ -49,8 +57,8 @@ _DEFUN(__fwalk, (ptr, function),
 
 /* Special version of __fwalk where the function pointer is a reentrant
    I/O function (e.g. _fclose_r).  */
-static int
-_DEFUN(__fwalk_reent, (ptr, reent_function),
+int
+_DEFUN(_fwalk_reent, (ptr, reent_function),
        struct _reent *ptr _AND
        register int (*reent_function) (struct _reent *, FILE *))
 {
@@ -58,51 +66,21 @@ _DEFUN(__fwalk_reent, (ptr, reent_function),
   register int n, ret = 0;
   register struct _glue *g;
 
+  /*
+   * It should be safe to walk the list without locking it;
+   * new nodes are only added to the end and none are ever
+   * removed.
+   *
+   * Avoid locking this list while walking it or else you will
+   * introduce a potential deadlock in [at least] refill.c.
+   */
   for (g = &ptr->__sglue; g != NULL; g = g->_next)
     for (fp = g->_iobs, n = g->_niobs; --n >= 0; fp++)
       if (fp->_flags != 0)
         {
-          if (fp->_flags != 0 && fp->_file != -1)
+          if (fp->_flags != 0 && fp->_flags != 1 && fp->_file != -1)
             ret |= (*reent_function) (ptr, fp);
         }
 
   return ret;
 }
-
-int
-_DEFUN(_fwalk, (ptr, function),
-       struct _reent *ptr _AND
-       register int (*function)(FILE *))
-{
-  register int ret = 0;
-
-  __sfp_lock_acquire ();
-
-  /* Must traverse given list for streams.  Note that _GLOBAL_REENT
-     only walked once in exit().  */
-  ret |= __fwalk (ptr, function);
-
-  __sfp_lock_release ();
-
-  return ret;
-}
-
-/* Special version of _fwalk which handles a function pointer to a
-   reentrant I/O function (e.g. _fclose_r).  */
-int
-_DEFUN(_fwalk_reent, (ptr, reent_function),
-       struct _reent *ptr _AND
-       register int (*reent_function) (struct _reent *, FILE *))
-{
-  register int ret = 0;
-
-  __sfp_lock_acquire ();
-
-  /* Must traverse given list for streams.  Note that _GLOBAL_REENT
-     only walked once in exit().  */
-  ret |= __fwalk_reent (ptr, reent_function);
-
-  __sfp_lock_release ();
-
-  return ret;
-}
diff --git a/newlib/libc/stdio/getc.c b/newlib/libc/stdio/getc.c
index 544ac73..5b1fa88 100644
--- a/newlib/libc/stdio/getc.c
+++ b/newlib/libc/stdio/getc.c
@@ -92,11 +92,9 @@ _DEFUN(_getc_r, (ptr, fp),
 {
   int result;
   CHECK_INIT (ptr, fp);
-  __sfp_lock_acquire ();
   _flockfile (fp);
   result = __sgetc_r (ptr, fp);
   _funlockfile (fp);
-  __sfp_lock_release ();
   return result;
 }
 
@@ -108,11 +106,9 @@ _DEFUN(getc, (fp),
 {
   int result;
   CHECK_INIT (_REENT, fp);
-  __sfp_lock_acquire ();
   _flockfile (fp);
   result = __sgetc_r (_REENT, fp);
   _funlockfile (fp);
-  __sfp_lock_release ();
   return result;
 }
 
diff --git a/newlib/libc/stdio/getdelim.c b/newlib/libc/stdio/getdelim.c
index 41460ab..23fc502 100644
--- a/newlib/libc/stdio/getdelim.c
+++ b/newlib/libc/stdio/getdelim.c
@@ -81,7 +81,6 @@ _DEFUN(__getdelim, (bufptr, n, delim, fp),
 
   CHECK_INIT (_REENT, fp);
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
 
   numbytes = *n;
@@ -131,7 +130,6 @@ _DEFUN(__getdelim, (bufptr, n, delim, fp),
     }
 
   _funlockfile (fp);
-  __sfp_lock_release ();
 
   /* if no input data, return failure */
   if (ptr == buf)
diff --git a/newlib/libc/stdio/gets.c b/newlib/libc/stdio/gets.c
index daa42e9..17d1443 100644
--- a/newlib/libc/stdio/gets.c
+++ b/newlib/libc/stdio/gets.c
@@ -79,14 +79,12 @@ _DEFUN(_gets_r, (ptr, buf),
   register int c;
   register char *s = buf;
 
-  __sfp_lock_acquire ();
   _flockfile (stdin);
   while ((c = __sgetc_r (ptr, stdin)) != '\n')
     if (c == EOF)
       if (s == buf)
 	{
 	  _funlockfile (stdin);
-	  __sfp_lock_release ();
 	  return NULL;
 	}
       else
@@ -95,7 +93,6 @@ _DEFUN(_gets_r, (ptr, buf),
       *s++ = c;
   *s = 0;
   _funlockfile (stdin);
-  __sfp_lock_release ();
   return buf;
 }
 
diff --git a/newlib/libc/stdio/local.h b/newlib/libc/stdio/local.h
index b69524c..9ca948d 100644
--- a/newlib/libc/stdio/local.h
+++ b/newlib/libc/stdio/local.h
@@ -54,6 +54,7 @@ int	      _EXFUN(_svfiwprintf_r,(struct _reent *, FILE *, const wchar_t *,
 				  va_list));
 extern FILE  *_EXFUN(__sfp,(struct _reent *));
 extern int    _EXFUN(__sflags,(struct _reent *,_CONST char*, int*));
+extern int    _EXFUN(__sflush_r,(struct _reent *,FILE *));
 extern int    _EXFUN(__srefill_r,(struct _reent *,FILE *));
 extern _READ_WRITE_RETURN_TYPE _EXFUN(__sread,(struct _reent *, void *, char *,
 					       int));
diff --git a/newlib/libc/stdio/refill.c b/newlib/libc/stdio/refill.c
index 27266ce..9d853f9 100644
--- a/newlib/libc/stdio/refill.c
+++ b/newlib/libc/stdio/refill.c
@@ -102,9 +102,19 @@ _DEFUN(__srefill_r, (ptr, fp),
    * flush all line buffered output files, per the ANSI C
    * standard.
    */
-
   if (fp->_flags & (__SLBF | __SNBF))
-    _CAST_VOID _fwalk (_GLOBAL_REENT, lflush);
+    {
+      /* Ignore this file in _fwalk to avoid potential deadlock. */
+      short orig_flags = fp->_flags;
+      fp->_flags = 1;
+      _CAST_VOID _fwalk (_GLOBAL_REENT, lflush);
+      fp->_flags = orig_flags;
+
+      /* Now flush this file without locking it. */
+      if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
+	__sflush_r (ptr, fp);
+    }
+
   fp->_p = fp->_bf._base;
   fp->_r = fp->_read (ptr, fp->_cookie, (char *) fp->_p, fp->_bf._size);
 #ifndef __CYGWIN__
diff --git a/newlib/libc/stdio/vfscanf.c b/newlib/libc/stdio/vfscanf.c
index fa4c598..42ebacd 100644
--- a/newlib/libc/stdio/vfscanf.c
+++ b/newlib/libc/stdio/vfscanf.c
@@ -494,7 +494,6 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap),
 # define GET_ARG(n, ap, type) (va_arg (ap, type))
 #endif
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
 
   ORIENT (fp, -1);
@@ -795,7 +794,6 @@ _DEFUN(__SVFSCANF_R, (rptr, fp, fmt0, ap),
 	   */
 	case '\0':		/* compat */
 	  _funlockfile (fp);
-	  __sfp_lock_release ();
 	  return EOF;
 
 	default:		/* compat */
@@ -1596,13 +1594,11 @@ input_failure:
      invalid format string), return EOF if no matches yet, else number
      of matches made prior to failure.  */
   _funlockfile (fp);
-  __sfp_lock_release ();
   return nassigned && !(fp->_flags & __SERR) ? nassigned : EOF;
 match_failure:
 all_done:
   /* Return number of matches, which can be 0 on match failure.  */
   _funlockfile (fp);
-  __sfp_lock_release ();
   return nassigned;
 }
 
diff --git a/newlib/libc/stdio/vfwscanf.c b/newlib/libc/stdio/vfwscanf.c
index 56df932..49ccf2f 100644
--- a/newlib/libc/stdio/vfwscanf.c
+++ b/newlib/libc/stdio/vfwscanf.c
@@ -434,7 +434,6 @@ _DEFUN(__SVFWSCANF_R, (rptr, fp, fmt0, ap),
 # define GET_ARG(n, ap, type) (va_arg (ap, type))
 #endif
 
-  __sfp_lock_acquire ();
   _flockfile (fp);
 
   ORIENT (fp, 1);
@@ -714,7 +713,6 @@ _DEFUN(__SVFWSCANF_R, (rptr, fp, fmt0, ap),
 	   */
 	case L'\0':		/* compat */
 	  _funlockfile (fp);
-	  __sfp_lock_release ();
 	  return EOF;
 
 	default:		/* compat */
@@ -1443,13 +1441,11 @@ input_failure:
      invalid format string), return EOF if no matches yet, else number
      of matches made prior to failure.  */
   _funlockfile (fp);
-  __sfp_lock_release ();
   return nassigned && !(fp->_flags & __SERR) ? nassigned : EOF;
 match_failure:
 all_done:
   /* Return number of matches, which can be 0 on match failure.  */
   _funlockfile (fp);
-  __sfp_lock_release ();
   return nassigned;
 }
 
diff --git a/newlib/libc/stdio64/freopen64.c b/newlib/libc/stdio64/freopen64.c
index 866d8c9..1e2ec78 100644
--- a/newlib/libc/stdio64/freopen64.c
+++ b/newlib/libc/stdio64/freopen64.c
@@ -97,7 +97,6 @@ _DEFUN (_freopen64_r, (ptr, file, mode, fp),
   int flags, oflags;
   int e = 0;
 
-  __sfp_lock_acquire ();
 
   CHECK_INIT (ptr, fp);
 
@@ -107,7 +106,6 @@ _DEFUN (_freopen64_r, (ptr, file, mode, fp),
     {
       _funlockfile(fp);
       _fclose_r (ptr, fp);
-      __sfp_lock_release ();
       return NULL;
     }
 
@@ -204,6 +202,7 @@ _DEFUN (_freopen64_r, (ptr, file, mode, fp),
 
   if (f < 0)
     {				/* did not get it after all */
+      __sfp_lock_acquire ();
       fp->_flags = 0;		/* set it free */
       ptr->_errno = e;		/* restore in case _close clobbered */
       _funlockfile(fp);
@@ -231,7 +230,6 @@ _DEFUN (_freopen64_r, (ptr, file, mode, fp),
   fp->_flags |= __SL64;
 
   _funlockfile(fp);
-  __sfp_lock_release ();
   return fp;
 }