Backported r185231 from trunk.

gcc/gthr.h

 /* Threads compatibility routines for libgcc2.  */
 /* Compile this one with gcc.  */
 /* Copyright (C) 1997, 1998, 2004, 2008, 2009 Free Software Foundation, Inc.
 
 This file is part of GCC.
 
 GCC is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free
 Software Foundation; either version 3, or (at your option) any later
 version.
@@ skipping 33 matching lines @@
      __gthread_recursive_mutex_t
 
    The threads interface must define the following macros:
 
      __GTHREAD_ONCE_INIT
                 to initialize __gthread_once_t
      __GTHREAD_MUTEX_INIT
                 to initialize __gthread_mutex_t to get a fast
                 non-recursive mutex.
      __GTHREAD_MUTEX_INIT_FUNCTION
-                some systems can't initialize a mutex without a
-                function call.  On such systems, define this to a
-                function which looks like this:
+                to initialize __gthread_mutex_t to get a fast
+                non-recursive mutex.
+                Define this to a function which looks like this:
                   void __GTHREAD_MUTEX_INIT_FUNCTION (__gthread_mutex_t *)
-                Don't define __GTHREAD_MUTEX_INIT in this case
+                Some systems can't initialize a mutex without a
+                function call.  Don't define __GTHREAD_MUTEX_INIT in this case.
      __GTHREAD_RECURSIVE_MUTEX_INIT
      __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION
                 as above, but for a recursive mutex.
 
    The threads interface must define the following static functions:
 
      int __gthread_once (__gthread_once_t *once, void (*func) ())
 
      int __gthread_key_create (__gthread_key_t *keyp, void (*dtor) (void *))
      int __gthread_key_delete (__gthread_key_t key)
@@ skipping 103 matching lines @@
 /* Fallback to single thread definitions.  */
 #else
 #include "gthr-single.h"
 #endif
 
 #ifndef HIDE_EXPORTS
 #pragma GCC visibility pop
 #endif
 
 #endif /* ! GCC_GTHR_H */