[v2,1/4] libio: Assume _IO_MTSAFE_IO

diff --git a/Makeconfig b/Makeconfig
index 0aa5fb0099..14fd013d57 100644
--- a/Makeconfig
+++ b/Makeconfig
@@ -1377,8 +1377,6 @@  endif
 # A sysdeps Makeconfig fragment may set libc-reentrant to yes.
 ifeq (yes,$(libc-reentrant))
 defines += -D_LIBC_REENTRANT
-
-libio-mtsafe = -D_IO_MTSAFE_IO
 endif
 
 # The name to give to a test in test results summaries.
diff --git a/debug/Makefile b/debug/Makefile
index 96029f32ee..6b7c5a1fcb 100644
--- a/debug/Makefile
+++ b/debug/Makefile
@@ -68,32 +68,23 @@  elide-routines.o := stack_chk_fail_local
 CFLAGS-stack_chk_fail.c += $(no-stack-protector)
 
 CFLAGS-backtrace.c += -fno-omit-frame-pointer -funwind-tables
-CFLAGS-sprintf_chk.c += $(libio-mtsafe)
-CFLAGS-snprintf_chk.c += $(libio-mtsafe)
-CFLAGS-vsprintf_chk.c += $(libio-mtsafe)
-CFLAGS-vsnprintf_chk.c += $(libio-mtsafe)
-CFLAGS-asprintf_chk.c += $(libio-mtsafe)
-CFLAGS-vasprintf_chk.c += $(libio-mtsafe)
-CFLAGS-obprintf_chk.c += $(libio-mtsafe)
-CFLAGS-dprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-vdprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-printf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-vprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-vfprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-gets_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fgets_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fgets_u_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fread_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fread_u_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-swprintf_chk.c += $(libio-mtsafe)
-CFLAGS-vswprintf_chk.c += $(libio-mtsafe)
-CFLAGS-wprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fwprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-vwprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-vfwprintf_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fgetws_chk.c += $(libio-mtsafe) -fexceptions
-CFLAGS-fgetws_u_chk.c += $(libio-mtsafe) -fexceptions
+CFLAGS-dprintf_chk.c += -fexceptions
+CFLAGS-vdprintf_chk.c += -fexceptions
+CFLAGS-printf_chk.c += -fexceptions
+CFLAGS-fprintf_chk.c += -fexceptions
+CFLAGS-vprintf_chk.c += -fexceptions
+CFLAGS-vfprintf_chk.c += -fexceptions
+CFLAGS-gets_chk.c += -fexceptions
+CFLAGS-fgets_chk.c += -fexceptions
+CFLAGS-fgets_u_chk.c += -fexceptions
+CFLAGS-fread_chk.c += -fexceptions
+CFLAGS-fread_u_chk.c += -fexceptions
+CFLAGS-wprintf_chk.c += -fexceptions
+CFLAGS-fwprintf_chk.c += -fexceptions
+CFLAGS-vwprintf_chk.c += -fexceptions
+CFLAGS-vfwprintf_chk.c += -fexceptions
+CFLAGS-fgetws_chk.c += -fexceptions
+CFLAGS-fgetws_u_chk.c += -fexceptions
 CFLAGS-read_chk.c += -fexceptions -fasynchronous-unwind-tables
 CFLAGS-pread_chk.c += -fexceptions -fasynchronous-unwind-tables
 CFLAGS-pread64_chk.c += -fexceptions -fasynchronous-unwind-tables
diff --git a/grp/Makefile b/grp/Makefile
index 48f3914e29..a3dc650cde 100644
--- a/grp/Makefile
+++ b/grp/Makefile
@@ -52,8 +52,8 @@  CFLAGS-getgrnam_r.c += -fexceptions
 CFLAGS-getgrent_r.c += -fexceptions
 CFLAGS-getgrent.c += -fexceptions
 CFLAGS-fgetgrent.c += -fexceptions
-CFLAGS-fgetgrent_r.c += -fexceptions $(libio-mtsafe)
-CFLAGS-putgrent.c += -fexceptions $(libio-mtsafe)
+CFLAGS-fgetgrent_r.c += -fexceptions
+CFLAGS-putgrent.c += -fexceptions
 CFLAGS-initgroups.c += -fexceptions
 CFLAGS-getgrgid.c += -fexceptions
 
diff --git a/gshadow/Makefile b/gshadow/Makefile
index eff303f538..3f9274ba99 100644
--- a/gshadow/Makefile
+++ b/gshadow/Makefile
@@ -31,8 +31,8 @@  tests = tst-gshadow tst-putsgent tst-fgetsgent_r
 CFLAGS-getsgent_r.c += -fexceptions
 CFLAGS-getsgent.c += -fexceptions
 CFLAGS-fgetsgent.c += -fexceptions
-CFLAGS-fgetsgent_r.c += -fexceptions $(libio-mtsafe)
-CFLAGS-putsgent.c += -fexceptions $(libio-mtsafe)
+CFLAGS-fgetsgent_r.c += -fexceptions
+CFLAGS-putsgent.c += -fexceptions
 CFLAGS-getsgnam.c += -fexceptions
 CFLAGS-getsgnam_r.c += -fexceptions
 
diff --git a/htl/Makefile b/htl/Makefile
index 0b403e2fca..cdc20141bf 100644
--- a/htl/Makefile
+++ b/htl/Makefile
@@ -174,8 +174,6 @@  install-lib-ldscripts := libpthread_syms.a
 
 include ../Makeconfig
 
-CFLAGS-lockfile.c = -D_IO_MTSAFE_IO
-
 all: # Make this the default target; it will be defined in Rules.
 
 subdir_install: $(inst_libdir)/libpthread2.a $(inst_libdir)/libpthread_syms.a
diff --git a/hurd/vpprintf.c b/hurd/vpprintf.c
index 67450399f5..7dbd4fca85 100644
--- a/hurd/vpprintf.c
+++ b/hurd/vpprintf.c
@@ -42,13 +42,9 @@  vpprintf (io_t port, const char *format, va_list arg)
   struct locked_FILE
   {
     struct _IO_cookie_file cfile;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
   } temp_f;
-#ifdef _IO_MTSAFE_IO
   temp_f.cfile.__fp.file._lock = &temp_f.lock;
-#endif
 
   _IO_cookie_init (&temp_f.cfile, _IO_NO_READS,
 		   (void *) port, (cookie_io_functions_t) { write: do_write });
diff --git a/include/stdio.h b/include/stdio.h
index 23b7fd288c..e9a7c77c24 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -1,5 +1,5 @@ 
 #ifndef _STDIO_H
-# if !defined _ISOMAC && defined _IO_MTSAFE_IO
+# if !defined _ISOMAC
 #  include <stdio-lock.h>
 # endif
 
diff --git a/libio/Makefile b/libio/Makefile
index e97387743f..88b4c20da6 100644
--- a/libio/Makefile
+++ b/libio/Makefile
@@ -92,8 +92,6 @@  routines += clearerr_u feof_u ferror_u fputc_u getc_u getchar_u		      \
 	    iofputs_u
 endif
 
-CPPFLAGS += $(libio-mtsafe)
-
 # Support for exception handling.
 CFLAGS-fileops.c += -fexceptions
 CFLAGS-fputc.c += -fexceptions
diff --git a/libio/clearerr.c b/libio/clearerr.c
index 47d9ceae1a..5aecee096b 100644
--- a/libio/clearerr.c
+++ b/libio/clearerr.c
@@ -26,7 +26,3 @@  clearerr (FILE *fp)
   _IO_clearerr (fp);
   _IO_funlockfile (fp);
 }
-
-#ifndef _IO_MTSAFE_IO
-weak_alias (clearerr, clearerr_unlocked)
-#endif
diff --git a/libio/feof.c b/libio/feof.c
index d6b95f40e8..7f79b2795e 100644
--- a/libio/feof.c
+++ b/libio/feof.c
@@ -41,8 +41,3 @@  _IO_feof (FILE *fp)
 }
 
 weak_alias (_IO_feof, feof)
-
-#ifndef _IO_MTSAFE_IO
-#undef feof_unlocked
-weak_alias (_IO_feof, feof_unlocked)
-#endif
diff --git a/libio/ferror.c b/libio/ferror.c
index bee2ef8f07..d2489c54d3 100644
--- a/libio/ferror.c
+++ b/libio/ferror.c
@@ -42,7 +42,3 @@  _IO_ferror (FILE *fp)
 
 weak_alias (_IO_ferror, ferror)
 
-#ifndef _IO_MTSAFE_IO
-#undef ferror_unlocked
-weak_alias (_IO_ferror, ferror_unlocked)
-#endif
diff --git a/libio/fileno.c b/libio/fileno.c
index ec479bedcf..3e5138fa0b 100644
--- a/libio/fileno.c
+++ b/libio/fileno.c
@@ -46,6 +46,6 @@  libc_hidden_weak (fileno)
 
 /* The fileno implementation for libio does not require locking because
    it only accesses once a single variable and this is already atomic
-   (at least at thread level).  Therefore we don't test _IO_MTSAFE_IO here.  */
+   (at least at thread level).  */
 
 weak_alias (__fileno, fileno_unlocked)
diff --git a/libio/fputc.c b/libio/fputc.c
index 8143f2c096..d29a9d0aee 100644
--- a/libio/fputc.c
+++ b/libio/fputc.c
@@ -39,8 +39,3 @@  fputc (int c, FILE *fp)
   _IO_release_lock (fp);
   return result;
 }
-
-#ifndef _IO_MTSAFE_IO
-#undef fputc_unlocked
-weak_alias (fputc, fputc_unlocked)
-#endif
diff --git a/libio/genops.c b/libio/genops.c
index 1b629eb695..ccfbcd149d 100644
--- a/libio/genops.c
+++ b/libio/genops.c
@@ -32,13 +32,10 @@ 
 #include <stdbool.h>
 #include <sched.h>
 
-#ifdef _IO_MTSAFE_IO
 static _IO_lock_t list_all_lock = _IO_lock_initializer;
-#endif
 
 static FILE *run_fp;
 
-#ifdef _IO_MTSAFE_IO
 static void
 flush_cleanup (void *not_used)
 {
@@ -46,7 +43,6 @@  flush_cleanup (void *not_used)
     _IO_funlockfile (run_fp);
   _IO_lock_unlock (list_all_lock);
 }
-#endif
 
 void
 _IO_un_link (struct _IO_FILE_plus *fp)
@@ -54,12 +50,10 @@  _IO_un_link (struct _IO_FILE_plus *fp)
   if (fp->file._flags & _IO_LINKED)
     {
       FILE **f;
-#ifdef _IO_MTSAFE_IO
       _IO_cleanup_region_start_noarg (flush_cleanup);
       _IO_lock_lock (list_all_lock);
       run_fp = (FILE *) fp;
       _IO_flockfile ((FILE *) fp);
-#endif
       if (_IO_list_all == NULL)
 	;
       else if (fp == _IO_list_all)
@@ -72,12 +66,10 @@  _IO_un_link (struct _IO_FILE_plus *fp)
 	      break;
 	    }
       fp->file._flags &= ~_IO_LINKED;
-#ifdef _IO_MTSAFE_IO
       _IO_funlockfile ((FILE *) fp);
       run_fp = NULL;
       _IO_lock_unlock (list_all_lock);
       _IO_cleanup_region_end (0);
-#endif
     }
 }
 libc_hidden_def (_IO_un_link)
@@ -88,20 +80,16 @@  _IO_link_in (struct _IO_FILE_plus *fp)
   if ((fp->file._flags & _IO_LINKED) == 0)
     {
       fp->file._flags |= _IO_LINKED;
-#ifdef _IO_MTSAFE_IO
       _IO_cleanup_region_start_noarg (flush_cleanup);
       _IO_lock_lock (list_all_lock);
       run_fp = (FILE *) fp;
       _IO_flockfile ((FILE *) fp);
-#endif
       fp->file._chain = (FILE *) _IO_list_all;
       _IO_list_all = fp;
-#ifdef _IO_MTSAFE_IO
       _IO_funlockfile ((FILE *) fp);
       run_fp = NULL;
       _IO_lock_unlock (list_all_lock);
       _IO_cleanup_region_end (0);
-#endif
     }
 }
 libc_hidden_def (_IO_link_in)
@@ -551,10 +539,8 @@  _IO_old_init (FILE *fp, int flags)
 #if _IO_JUMPS_OFFSET
   fp->_vtable_offset = 0;
 #endif
-#ifdef _IO_MTSAFE_IO
   if (fp->_lock != NULL)
     _IO_lock_init (*fp->_lock);
-#endif
 }
 
 void
@@ -617,10 +603,8 @@  _IO_default_finish (FILE *fp, int dummy)
 
   _IO_un_link ((struct _IO_FILE_plus *) fp);
 
-#ifdef _IO_MTSAFE_IO
   if (fp->_lock != NULL)
     _IO_lock_fini (*fp->_lock);
-#endif
 }
 libc_hidden_def (_IO_default_finish)
 
@@ -687,10 +671,8 @@  _IO_flush_all_lockp (int do_lock)
   int result = 0;
   FILE *fp;
 
-#ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (flush_cleanup);
   _IO_lock_lock (list_all_lock);
-#endif
 
   for (fp = (FILE *) _IO_list_all; fp != NULL; fp = fp->_chain)
     {
@@ -711,10 +693,8 @@  _IO_flush_all_lockp (int do_lock)
       run_fp = NULL;
     }
 
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (list_all_lock);
   _IO_cleanup_region_end (0);
-#endif
 
   return result;
 }
@@ -733,10 +713,8 @@  _IO_flush_all_linebuffered (void)
 {
   FILE *fp;
 
-#ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (flush_cleanup);
   _IO_lock_lock (list_all_lock);
-#endif
 
   for (fp = (FILE *) _IO_list_all; fp != NULL; fp = fp->_chain)
     {
@@ -750,10 +728,8 @@  _IO_flush_all_linebuffered (void)
       run_fp = NULL;
     }
 
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (list_all_lock);
   _IO_cleanup_region_end (0);
-#endif
 }
 libc_hidden_def (_IO_flush_all_linebuffered)
 weak_alias (_IO_flush_all_linebuffered, _flushlbf)
@@ -782,10 +758,8 @@  _IO_unbuffer_all (void)
 {
   FILE *fp;
 
-#ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (flush_cleanup);
   _IO_lock_lock (list_all_lock);
-#endif
 
   for (fp = (FILE *) _IO_list_all; fp; fp = fp->_chain)
     {
@@ -800,7 +774,6 @@  _IO_unbuffer_all (void)
 	  /* Iff stream is un-orientated, it wasn't used. */
 	  && (legacy || fp->_mode != 0))
 	{
-#ifdef _IO_MTSAFE_IO
 	  int cnt;
 #define MAXTRIES 2
 	  for (cnt = 0; cnt < MAXTRIES; ++cnt)
@@ -810,7 +783,6 @@  _IO_unbuffer_all (void)
 	      /* Give the other thread time to finish up its use of the
 		 stream.  */
 	      __sched_yield ();
-#endif
 
 	  if (! legacy && ! dealloc_buffers && !(fp->_flags & _IO_USER_BUF))
 	    {
@@ -826,10 +798,8 @@  _IO_unbuffer_all (void)
 	  if (! legacy && fp->_mode > 0)
 	    _IO_wsetb (fp, NULL, NULL, 0);
 
-#ifdef _IO_MTSAFE_IO
 	  if (cnt < MAXTRIES && fp->_lock != NULL)
 	    _IO_lock_unlock (*fp->_lock);
-#endif
 	}
 
       /* Make sure that never again the wide char functions can be
@@ -838,10 +808,8 @@  _IO_unbuffer_all (void)
 	fp->_mode = -1;
     }
 
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (list_all_lock);
   _IO_cleanup_region_end (0);
-#endif
 }
 
 
@@ -1092,27 +1060,21 @@  libc_hidden_def (_IO_iter_file)
 void
 _IO_list_lock (void)
 {
-#ifdef _IO_MTSAFE_IO
   _IO_lock_lock (list_all_lock);
-#endif
 }
 libc_hidden_def (_IO_list_lock)
 
 void
 _IO_list_unlock (void)
 {
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (list_all_lock);
-#endif
 }
 libc_hidden_def (_IO_list_unlock)
 
 void
 _IO_list_resetlock (void)
 {
-#ifdef _IO_MTSAFE_IO
   _IO_lock_init (list_all_lock);
-#endif
 }
 libc_hidden_def (_IO_list_resetlock)
 
diff --git a/libio/getc.c b/libio/getc.c
index 55a6cc479a..8c79cf702f 100644
--- a/libio/getc.c
+++ b/libio/getc.c
@@ -46,9 +46,3 @@  _IO_getc (FILE *fp)
 
 weak_alias (_IO_getc, getc)
 weak_alias (_IO_getc, fgetc)
-
-#ifndef _IO_MTSAFE_IO
-#undef getc_unlocked
-weak_alias (_IO_getc, getc_unlocked)
-weak_alias (_IO_getc, fgetc_unlocked)
-#endif
diff --git a/libio/getchar.c b/libio/getchar.c
index 6ceff06a84..e0f4f471b3 100644
--- a/libio/getchar.c
+++ b/libio/getchar.c
@@ -39,9 +39,4 @@  getchar (void)
   result = _IO_getc_unlocked (stdin);
   _IO_release_lock (stdin);
   return result;
-}
-
-#ifndef _IO_MTSAFE_IO
-#undef getchar_unlocked
-weak_alias (getchar, getchar_unlocked)
-#endif
+}
\ No newline at end of file
diff --git a/libio/iofdopen.c b/libio/iofdopen.c
index 47b602d3c2..b8d082ebc5 100644
--- a/libio/iofdopen.c
+++ b/libio/iofdopen.c
@@ -37,9 +37,7 @@  _IO_new_fdopen (int fd, const char *mode)
   struct locked_FILE
   {
     struct _IO_FILE_plus fp;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
     struct _IO_wide_data wd;
   } *new_f;
   int i;
@@ -122,9 +120,7 @@  _IO_new_fdopen (int fd, const char *mode)
   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fp.file._lock = &new_f->lock;
-#endif
   _IO_no_init (&new_f->fp.file, 0, 0, &new_f->wd,
 #if _G_HAVE_MMAP
 	       (use_mmap && (read_write & _IO_NO_WRITES))
diff --git a/libio/iofflush.c b/libio/iofflush.c
index 5b542664a8..6ea046cf48 100644
--- a/libio/iofflush.c
+++ b/libio/iofflush.c
@@ -46,10 +46,3 @@  libc_hidden_def (_IO_fflush)
 
 weak_alias (_IO_fflush, fflush)
 libc_hidden_weak (fflush)
-
-#ifndef _IO_MTSAFE_IO
-strong_alias (_IO_fflush, __fflush_unlocked)
-libc_hidden_def (__fflush_unlocked)
-weak_alias (_IO_fflush, fflush_unlocked)
-libc_hidden_weak (fflush_unlocked)
-#endif
diff --git a/libio/iofgets.c b/libio/iofgets.c
index 58d30fca96..f19526de46 100644
--- a/libio/iofgets.c
+++ b/libio/iofgets.c
@@ -66,10 +66,3 @@  _IO_fgets (char *buf, int n, FILE *fp)
 }
 
 weak_alias (_IO_fgets, fgets)
-
-# ifndef _IO_MTSAFE_IO
-strong_alias (_IO_fgets, __fgets_unlocked)
-libc_hidden_def (__fgets_unlocked)
-weak_alias (_IO_fgets, fgets_unlocked)
-libc_hidden_weak (fgets_unlocked)
-# endif
diff --git a/libio/iofopen.c b/libio/iofopen.c
index e7471fa3ae..777f8c9e1c 100644
--- a/libio/iofopen.c
+++ b/libio/iofopen.c
@@ -58,17 +58,13 @@  __fopen_internal (const char *filename, const char *mode, int is32)
   struct locked_FILE
   {
     struct _IO_FILE_plus fp;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
     struct _IO_wide_data wd;
   } *new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
 
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fp.file._lock = &new_f->lock;
-#endif
   _IO_no_init (&new_f->fp.file, 0, 0, &new_f->wd, &_IO_wfile_jumps);
   _IO_JUMPS (&new_f->fp) = &_IO_file_jumps;
   _IO_new_file_init_internal (&new_f->fp);
diff --git a/libio/iofopncook.c b/libio/iofopncook.c
index e108ad2199..16bcc7f4a3 100644
--- a/libio/iofopncook.c
+++ b/libio/iofopncook.c
@@ -179,9 +179,7 @@  _IO_fopencookie (void *cookie, const char *mode,
   struct locked_FILE
   {
     struct _IO_cookie_file cfile;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
   } *new_f;
 
   switch (*mode++)
@@ -205,9 +203,7 @@  _IO_fopencookie (void *cookie, const char *mode,
   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->cfile.__fp.file._lock = &new_f->lock;
-#endif
 
   _IO_cookie_init (&new_f->cfile, read_write, cookie, io_functions);
 
diff --git a/libio/iofputs.c b/libio/iofputs.c
index 999e069877..f8e0ee7200 100644
--- a/libio/iofputs.c
+++ b/libio/iofputs.c
@@ -44,10 +44,3 @@  libc_hidden_def (_IO_fputs)
 
 weak_alias (_IO_fputs, fputs)
 libc_hidden_weak (fputs)
-
-# ifndef _IO_MTSAFE_IO
-strong_alias (_IO_fputs, __fputs_unlocked)
-libc_hidden_def (__fputs_unlocked)
-weak_alias (_IO_fputs, fputs_unlocked)
-libc_hidden_ver (_IO_fputs, fputs_unlocked)
-# endif
diff --git a/libio/iofread.c b/libio/iofread.c
index d358136953..66f69ac93f 100644
--- a/libio/iofread.c
+++ b/libio/iofread.c
@@ -42,9 +42,3 @@  _IO_fread (void *buf, size_t size, size_t count, FILE *fp)
 libc_hidden_def (_IO_fread)
 
 weak_alias (_IO_fread, fread)
-
-# ifndef _IO_MTSAFE_IO
-strong_alias (_IO_fread, __fread_unlocked)
-libc_hidden_def (__fread_unlocked)
-weak_alias (_IO_fread, fread_unlocked)
-# endif
diff --git a/libio/iofwrite.c b/libio/iofwrite.c
index f86b5458da..ff741fec8e 100644
--- a/libio/iofwrite.c
+++ b/libio/iofwrite.c
@@ -24,6 +24,7 @@ 
    This exception applies to code released by its copyright holders
    in files containing the exception.  */
 
+#include <stdio.h>
 #include "libioP.h"
 
 size_t
@@ -49,10 +50,5 @@  _IO_fwrite (const void *buf, size_t size, size_t count, FILE *fp)
 }
 libc_hidden_def (_IO_fwrite)
 
-# include <stdio.h>
 weak_alias (_IO_fwrite, fwrite)
 libc_hidden_weak (fwrite)
-# ifndef _IO_MTSAFE_IO
-weak_alias (_IO_fwrite, fwrite_unlocked)
-libc_hidden_weak (fwrite_unlocked)
-# endif
diff --git a/libio/iopopen.c b/libio/iopopen.c
index 06778cf110..676c739aba 100644
--- a/libio/iopopen.c
+++ b/libio/iopopen.c
@@ -49,7 +49,6 @@  static const struct _IO_jump_t _IO_proc_jumps;
 
 static struct _IO_proc_file *proc_file_chain;
 
-#ifdef _IO_MTSAFE_IO
 static _IO_lock_t proc_file_chain_lock = _IO_lock_initializer;
 
 static void
@@ -57,7 +56,6 @@  unlock (void *not_used)
 {
   _IO_lock_unlock (proc_file_chain_lock);
 }
-#endif
 
 /* POSIX states popen shall ensure that any streams from previous popen()
    calls that remain open in the parent process should be closed in the new
@@ -189,16 +187,12 @@  _IO_new_proc_open (FILE *fp, const char *command, const char *mode)
       child_pipe_fd) != 0)
     goto spawn_failure;
 
-#ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (unlock);
   _IO_lock_lock (proc_file_chain_lock);
-#endif
   spawn_ok = spawn_process (&fa, fp, command, do_cloexec, pipe_fds,
 			    parent_end, child_end, child_pipe_fd);
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (proc_file_chain_lock);
   _IO_cleanup_region_end (0);
-#endif
 
   __posix_spawn_file_actions_destroy (&fa);
 
@@ -221,18 +215,14 @@  _IO_new_popen (const char *command, const char *mode)
   struct locked_FILE
   {
     struct _IO_proc_file fpx;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
   } *new_f;
   FILE *fp;
 
   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fpx.file.file._lock = &new_f->lock;
-#endif
   fp = &new_f->fpx.file.file;
   _IO_init_internal (fp, 0);
   _IO_JUMPS (&new_f->fpx.file) = &_IO_proc_jumps;
@@ -254,10 +244,8 @@  _IO_new_proc_close (FILE *fp)
   int status = -1;
 
   /* Unlink from proc_file_chain. */
-#ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (unlock);
   _IO_lock_lock (proc_file_chain_lock);
-#endif
   for ( ; *ptr != NULL; ptr = &(*ptr)->next)
     {
       if (*ptr == (_IO_proc_file *) fp)
@@ -267,10 +255,8 @@  _IO_new_proc_close (FILE *fp)
 	  break;
 	}
     }
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (proc_file_chain_lock);
   _IO_cleanup_region_end (0);
-#endif
 
   if (status < 0 || __close_nocancel (_IO_fileno(fp)) < 0)
     return -1;
diff --git a/libio/iovdprintf.c b/libio/iovdprintf.c
index 1e483868c9..4c5a90e58d 100644
--- a/libio/iovdprintf.c
+++ b/libio/iovdprintf.c
@@ -35,9 +35,7 @@  __vdprintf_internal (int d, const char *format, va_list arg,
   struct _IO_wide_data wd;
   int done;
 
-#ifdef _IO_MTSAFE_IO
   tmpfil.file._lock = NULL;
-#endif
   _IO_no_init (&tmpfil.file, _IO_USER_LOCK, 0, &wd, &_IO_wfile_jumps);
   _IO_JUMPS (&tmpfil) = &_IO_file_jumps;
   _IO_new_file_init_internal (&tmpfil);
diff --git a/libio/iovsprintf.c b/libio/iovsprintf.c
index 72c67bf27b..cbe59f6fec 100644
--- a/libio/iovsprintf.c
+++ b/libio/iovsprintf.c
@@ -73,9 +73,7 @@  __vsprintf_internal (char *string, size_t maxlen,
   _IO_strfile sf;
   int ret;
 
-#ifdef _IO_MTSAFE_IO
   sf._sbf._f._lock = NULL;
-#endif
   _IO_no_init (&sf._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
   /* When called from fortified sprintf/vsprintf, erase the destination
      buffer and try to detect overflows.  When called from regular
diff --git a/libio/libio.h b/libio/libio.h
index d0184df878..42ff6143af 100644
--- a/libio/libio.h
+++ b/libio/libio.h
@@ -36,7 +36,7 @@ 
 
 #include <stdio.h>
 
-#if defined _IO_MTSAFE_IO && !defined _IO_lock_t_defined
+#if !defined _IO_lock_t_defined
 # error "Someone forgot to include stdio-lock.h"
 #endif
 
@@ -198,10 +198,13 @@  extern void _IO_flockfile (FILE *) __THROW;
 extern void _IO_funlockfile (FILE *) __THROW;
 extern int _IO_ftrylockfile (FILE *) __THROW;
 
-#define _IO_peekc(_fp) _IO_peekc_unlocked (_fp)
-#define _IO_flockfile(_fp) /**/
-#define _IO_funlockfile(_fp) ((void) 0)
-#define _IO_ftrylockfile(_fp) /**/
+#define _IO_peekc(_fp) _IO_peekc_locked (_fp)
+#define _IO_flockfile(_fp) \
+  if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_lock (*(_fp)->_lock)
+#define _IO_funlockfile(_fp) \
+  if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_unlock (*(_fp)->_lock)
+#define _IO_ftrylockfile(__fp) \
+  if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_trylock (*(_fp)->_lock)
 #ifndef _IO_cleanup_region_start
 #define _IO_cleanup_region_start(_fct, _fp) /**/
 #endif
@@ -272,17 +275,4 @@  libc_hidden_proto (_IO_padn)
 libc_hidden_proto (_IO_putc)
 libc_hidden_proto (_IO_sgetn)
 
-#ifdef _IO_MTSAFE_IO
-# undef _IO_peekc
-# undef _IO_flockfile
-# undef _IO_funlockfile
-# undef _IO_ftrylockfile
-
-# define _IO_peekc(_fp) _IO_peekc_locked (_fp)
-# define _IO_flockfile(_fp) \
-  if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_lock (*(_fp)->_lock)
-# define _IO_funlockfile(_fp) \
-  if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_unlock (*(_fp)->_lock)
-#endif /* _IO_MTSAFE_IO */
-
 #endif /* _LIBIO_H */
diff --git a/libio/libioP.h b/libio/libioP.h
index ba4fdbd200..114084b83a 100644
--- a/libio/libioP.h
+++ b/libio/libioP.h
@@ -803,33 +803,18 @@  extern int __vfwscanf_internal (FILE *fp, const wchar_t *format, va_list argp,
 
 extern int _IO_vscanf (const char *, va_list) __THROW;
 
-#ifdef _IO_MTSAFE_IO
 /* check following! */
-# ifdef _IO_USE_OLD_IO_FILE
-#  define FILEBUF_LITERAL(CHAIN, FLAGS, FD, WDP) \
+#ifdef _IO_USE_OLD_IO_FILE
+# define FILEBUF_LITERAL(CHAIN, FLAGS, FD, WDP) \
        { _IO_MAGIC+_IO_LINKED+_IO_IS_FILEBUF+FLAGS, \
 	 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, (FILE *) CHAIN, FD, \
 	 0, _IO_pos_BAD, 0, 0, { 0 }, &_IO_stdfile_##FD##_lock }
-# else
-#  define FILEBUF_LITERAL(CHAIN, FLAGS, FD, WDP) \
-       { _IO_MAGIC+_IO_LINKED+_IO_IS_FILEBUF+FLAGS, \
-	 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, (FILE *) CHAIN, FD, \
-	 0, _IO_pos_BAD, 0, 0, { 0 }, &_IO_stdfile_##FD##_lock, _IO_pos_BAD,\
-	 NULL, WDP, 0 }
-# endif
 #else
-# ifdef _IO_USE_OLD_IO_FILE
-#  define FILEBUF_LITERAL(CHAIN, FLAGS, FD, WDP) \
+# define FILEBUF_LITERAL(CHAIN, FLAGS, FD, WDP) \
        { _IO_MAGIC+_IO_LINKED+_IO_IS_FILEBUF+FLAGS, \
 	 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, (FILE *) CHAIN, FD, \
-	 0, _IO_pos_BAD }
-# else
-#  define FILEBUF_LITERAL(CHAIN, FLAGS, FD, WDP) \
-       { _IO_MAGIC+_IO_LINKED+_IO_IS_FILEBUF+FLAGS, \
-	 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, (FILE *) CHAIN, FD, \
-	 0, _IO_pos_BAD, 0, 0, { 0 }, 0, _IO_pos_BAD, \
+	 0, _IO_pos_BAD, 0, 0, { 0 }, &_IO_stdfile_##FD##_lock, _IO_pos_BAD,\
 	 NULL, WDP, 0 }
-# endif
 #endif
 
 #if SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_1)
@@ -884,13 +869,6 @@  _IO_acquire_lock_fct (FILE **p)
     _IO_funlockfile (fp);
 }
 
-#if !defined _IO_MTSAFE_IO && IS_IN (libc)
-# define _IO_acquire_lock(_fp)						      \
-  do {
-# define _IO_release_lock(_fp)						      \
-  } while (0)
-#endif
-
 /* Collect all vtables in a special section for vtable verification.
    These symbols cover the extent of this section.  */
 symbol_set_declare (__libc_IO_vtables)
diff --git a/libio/memstream.c b/libio/memstream.c
index 1ae8cd9544..7ab61876ba 100644
--- a/libio/memstream.c
+++ b/libio/memstream.c
@@ -66,9 +66,7 @@  __open_memstream (char **bufloc, size_t *sizeloc)
   struct locked_FILE
   {
     struct _IO_FILE_memstream fp;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
     struct _IO_wide_data wd;
   } *new_f;
   char *buf;
@@ -76,9 +74,7 @@  __open_memstream (char **bufloc, size_t *sizeloc)
   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fp._sf._sbf._f._lock = &new_f->lock;
-#endif
 
   buf = calloc (1, BUFSIZ);
   if (buf == NULL)
diff --git a/libio/obprintf.c b/libio/obprintf.c
index c220be9adc..ed0f39d85a 100644
--- a/libio/obprintf.c
+++ b/libio/obprintf.c
@@ -127,9 +127,7 @@  __obstack_vprintf_internal (struct obstack *obstack, const char *format,
   int size;
   int room;
 
-#ifdef _IO_MTSAFE_IO
   new_f.ofile.file.file._lock = NULL;
-#endif
 
   _IO_no_init (&new_f.ofile.file.file, _IO_USER_LOCK, -1, NULL, NULL);
   _IO_JUMPS (&new_f.ofile.file) = &_IO_obstack_jumps;
diff --git a/libio/oldiofdopen.c b/libio/oldiofdopen.c
index 1ce050f1f4..0b0097e9e2 100644
--- a/libio/oldiofdopen.c
+++ b/libio/oldiofdopen.c
@@ -41,9 +41,7 @@  _IO_old_fdopen (int fd, const char *mode)
   struct locked_FILE
   {
     struct _IO_FILE_complete_plus fp;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
   } *new_f;
   int fd_flags;
 
@@ -96,9 +94,7 @@  _IO_old_fdopen (int fd, const char *mode)
   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fp.file._file._lock = &new_f->lock;
-#endif
   _IO_old_init (&new_f->fp.file._file, 0);
   _IO_JUMPS_FILE_plus (&new_f->fp) = &_IO_old_file_jumps;
   _IO_old_file_init_internal ((struct _IO_FILE_plus *) &new_f->fp);
diff --git a/libio/oldiofopen.c b/libio/oldiofopen.c
index c73911fdd8..f3abd9ee07 100644
--- a/libio/oldiofopen.c
+++ b/libio/oldiofopen.c
@@ -39,16 +39,12 @@  _IO_old_fopen (const char *filename, const char *mode)
   struct locked_FILE
   {
     struct _IO_FILE_complete_plus fp;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
   } *new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
 
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fp.file._file._lock = &new_f->lock;
-#endif
   _IO_old_init (&new_f->fp.file._file, 0);
   _IO_JUMPS_FILE_plus (&new_f->fp) = &_IO_old_file_jumps;
   _IO_old_file_init_internal ((struct _IO_FILE_plus *) &new_f->fp);
diff --git a/libio/oldiopopen.c b/libio/oldiopopen.c
index f9149413e8..e24acf752e 100644
--- a/libio/oldiopopen.c
+++ b/libio/oldiopopen.c
@@ -47,7 +47,6 @@  typedef struct _IO_proc_file _IO_proc_file;
 
 static struct _IO_proc_file *old_proc_file_chain;
 
-#ifdef _IO_MTSAFE_IO
 static _IO_lock_t proc_file_chain_lock = _IO_lock_initializer;
 
 static void
@@ -55,7 +54,6 @@  unlock (void *not_used)
 {
   _IO_lock_unlock (proc_file_chain_lock);
 }
-#endif
 
 FILE *
 attribute_compat_text_section
@@ -118,16 +116,12 @@  _IO_old_proc_open (FILE *fp, const char *command, const char *mode)
   _IO_fileno (fp) = parent_end;
 
   /* Link into old_proc_file_chain. */
-#ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (unlock);
   _IO_lock_lock (proc_file_chain_lock);
-#endif
   ((_IO_proc_file *) fp)->next = old_proc_file_chain;
   old_proc_file_chain = (_IO_proc_file *) fp;
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (proc_file_chain_lock);
   _IO_cleanup_region_end (0);
-#endif
 
   _IO_mask_flags (fp, read_or_write, _IO_NO_READS|_IO_NO_WRITES);
   return fp;
@@ -140,18 +134,14 @@  _IO_old_popen (const char *command, const char *mode)
   struct locked_FILE
   {
     struct _IO_proc_file fpx;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
   } *new_f;
   FILE *fp;
 
   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fpx.file.file._file._lock = &new_f->lock;
-#endif
   fp = &new_f->fpx.file.file._file;
   _IO_old_init (fp, 0);
   _IO_JUMPS_FILE_plus (&new_f->fpx.file) = &_IO_old_proc_jumps;
@@ -174,10 +164,8 @@  _IO_old_proc_close (FILE *fp)
   int status = -1;
 
   /* Unlink from old_proc_file_chain. */
-#ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (unlock);
   _IO_lock_lock (proc_file_chain_lock);
-#endif
   for ( ; *ptr != NULL; ptr = &(*ptr)->next)
     {
       if (*ptr == (_IO_proc_file *) fp)
@@ -187,10 +175,8 @@  _IO_old_proc_close (FILE *fp)
 	  break;
 	}
     }
-#ifdef _IO_MTSAFE_IO
   _IO_lock_unlock (proc_file_chain_lock);
   _IO_cleanup_region_end (0);
-#endif
 
   if (status < 0 || __close (_IO_fileno(fp)) < 0)
     return -1;
diff --git a/libio/oldstdfiles.c b/libio/oldstdfiles.c
index 81a7f4f64d..30d8e39ef9 100644
--- a/libio/oldstdfiles.c
+++ b/libio/oldstdfiles.c
@@ -33,16 +33,10 @@ 
 #define _IO_USE_OLD_IO_FILE
 #include "libioP.h"
 
-#ifdef _IO_MTSAFE_IO
 #define DEF_STDFILE(NAME, FD, CHAIN, FLAGS) \
   static _IO_lock_t _IO_stdfile_##FD##_lock = _IO_lock_initializer; \
   struct _IO_FILE_plus NAME \
     = {FILEBUF_LITERAL(CHAIN, FLAGS, FD, NULL), &_IO_old_file_jumps};
-#else
-#define DEF_STDFILE(NAME, FD, CHAIN, FLAGS) \
-  struct _IO_FILE_plus NAME \
-    = {FILEBUF_LITERAL(CHAIN, FLAGS, FD, NULL), &_IO_old_file_jumps};
-#endif
 
 DEF_STDFILE(_IO_stdin_, 0, 0, _IO_NO_WRITES);
 DEF_STDFILE(_IO_stdout_, 1, &_IO_stdin_, _IO_NO_READS);
diff --git a/libio/putc.c b/libio/putc.c
index 7036c5b6bb..44e30649c9 100644
--- a/libio/putc.c
+++ b/libio/putc.c
@@ -37,8 +37,3 @@  libc_hidden_def (_IO_putc)
 #undef putc
 
 weak_alias (_IO_putc, putc)
-
-#ifndef _IO_MTSAFE_IO
-#undef putc_unlocked
-weak_alias (_IO_putc, putc_unlocked)
-#endif
diff --git a/libio/putchar.c b/libio/putchar.c
index 7eff3d5f94..9aff59c090 100644
--- a/libio/putchar.c
+++ b/libio/putchar.c
@@ -29,8 +29,3 @@  putchar (int c)
   _IO_release_lock (stdout);
   return result;
 }
-
-#if defined weak_alias && !defined _IO_MTSAFE_IO
-#undef putchar_unlocked
-weak_alias (putchar, putchar_unlocked)
-#endif
diff --git a/libio/stdfiles.c b/libio/stdfiles.c
index 31cf72dfd0..b5c1dc4208 100644
--- a/libio/stdfiles.c
+++ b/libio/stdfiles.c
@@ -32,22 +32,13 @@ 
 
 #include "libioP.h"
 
-#ifdef _IO_MTSAFE_IO
-# define DEF_STDFILE(NAME, FD, CHAIN, FLAGS) \
+#define DEF_STDFILE(NAME, FD, CHAIN, FLAGS) \
   static _IO_lock_t _IO_stdfile_##FD##_lock = _IO_lock_initializer; \
   static struct _IO_wide_data _IO_wide_data_##FD \
     = { ._wide_vtable = &_IO_wfile_jumps }; \
   struct _IO_FILE_plus NAME \
     = {FILEBUF_LITERAL(CHAIN, FLAGS, FD, &_IO_wide_data_##FD), \
        &_IO_file_jumps};
-#else
-# define DEF_STDFILE(NAME, FD, CHAIN, FLAGS) \
-  static struct _IO_wide_data _IO_wide_data_##FD \
-    = { ._wide_vtable = &_IO_wfile_jumps }; \
-  struct _IO_FILE_plus NAME \
-    = {FILEBUF_LITERAL(CHAIN, FLAGS, FD, &_IO_wide_data_##FD), \
-       &_IO_file_jumps};
-#endif
 
 DEF_STDFILE(_IO_2_1_stdin_, 0, 0, _IO_NO_WRITES);
 DEF_STDFILE(_IO_2_1_stdout_, 1, &_IO_2_1_stdin_, _IO_NO_READS);
diff --git a/libio/vasprintf.c b/libio/vasprintf.c
index 4430a266c6..c90a21cb6f 100644
--- a/libio/vasprintf.c
+++ b/libio/vasprintf.c
@@ -45,9 +45,7 @@  __vasprintf_internal (char **result_ptr, const char *format, va_list args,
   string = (char *) malloc (init_string_size);
   if (string == NULL)
     return -1;
-#ifdef _IO_MTSAFE_IO
   sf._sbf._f._lock = NULL;
-#endif
   _IO_no_init (&sf._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
   _IO_JUMPS (&sf._sbf) = &_IO_str_jumps;
   _IO_str_init_static_internal (&sf, string, init_string_size, string);
diff --git a/libio/vsnprintf.c b/libio/vsnprintf.c
index 8dae66761d..5aa01665d8 100644
--- a/libio/vsnprintf.c
+++ b/libio/vsnprintf.c
@@ -95,9 +95,7 @@  __vsnprintf_internal (char *string, size_t maxlen, const char *format,
 {
   _IO_strnfile sf;
   int ret;
-#ifdef _IO_MTSAFE_IO
   sf.f._sbf._f._lock = NULL;
-#endif
 
   /* We need to handle the special case where MAXLEN is 0.  Use the
      overflow buffer right from the start.  */
diff --git a/libio/vswprintf.c b/libio/vswprintf.c
index 5a9ccdff3e..c6f4706573 100644
--- a/libio/vswprintf.c
+++ b/libio/vswprintf.c
@@ -95,9 +95,7 @@  __vswprintf_internal (wchar_t *string, size_t maxlen, const wchar_t *format,
   _IO_wstrnfile sf;
   int ret;
   struct _IO_wide_data wd;
-#ifdef _IO_MTSAFE_IO
   sf.f._sbf._f._lock = NULL;
-#endif
 
   if (maxlen == 0)
     /* Since we have to write at least the terminating L'\0' a buffer
diff --git a/libio/wgenops.c b/libio/wgenops.c
index e7ea75aed2..96e10f6d1c 100644
--- a/libio/wgenops.c
+++ b/libio/wgenops.c
@@ -185,10 +185,8 @@  _IO_wdefault_finish (FILE *fp, int dummy)
       fp->_IO_save_base = NULL;
     }
 
-#ifdef _IO_MTSAFE_IO
   if (fp->_lock != NULL)
     _IO_lock_fini (*fp->_lock);
-#endif
 
   _IO_un_link ((struct _IO_FILE_plus *) fp);
 }
diff --git a/libio/wmemstream.c b/libio/wmemstream.c
index e7f898c7fb..9366ef4aad 100644
--- a/libio/wmemstream.c
+++ b/libio/wmemstream.c
@@ -67,9 +67,7 @@  open_wmemstream (wchar_t **bufloc, size_t *sizeloc)
   struct locked_FILE
   {
     struct _IO_FILE_wmemstream fp;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
     struct _IO_wide_data wd;
   } *new_f;
   wchar_t *buf;
@@ -77,9 +75,7 @@  open_wmemstream (wchar_t **bufloc, size_t *sizeloc)
   new_f = (struct locked_FILE *) malloc (sizeof (struct locked_FILE));
   if (new_f == NULL)
     return NULL;
-#ifdef _IO_MTSAFE_IO
   new_f->fp._sf._sbf._f._lock = &new_f->lock;
-#endif
 
   buf = calloc (1, BUFSIZ);
   if (buf == NULL)
diff --git a/nptl/Makefile b/nptl/Makefile
index b585663974..a85da416de 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -432,9 +432,6 @@  $(objpfx)multidir.mk: $(common-objpfx)config.make
 
 endif
 
-CFLAGS-ftrylockfile.c += $(libio-mtsafe)
-CFLAGS-funlockfile.c += $(libio-mtsafe)
-
 link-libc-static := $(common-objpfx)libc.a $(static-gnulib) \
 		    $(common-objpfx)libc.a
 
diff --git a/pwd/Makefile b/pwd/Makefile
index 848e7d0e12..da8e84c46c 100644
--- a/pwd/Makefile
+++ b/pwd/Makefile
@@ -37,6 +37,5 @@  ifeq ($(have-thread-library),yes)
 CFLAGS-getpwent_r.c += -fexceptions
 CFLAGS-getpwent.c += -fexceptions
 CFLAGS-getpw.c += -fexceptions
-CFLAGS-fgetpwent_r.c += $(libio-mtsafe)
 
 endif
diff --git a/shadow/Makefile b/shadow/Makefile
index b9faa3aa53..1b4ee5d50f 100644
--- a/shadow/Makefile
+++ b/shadow/Makefile
@@ -32,8 +32,8 @@  tests = tst-shadow tst-putspent
 CFLAGS-getspent_r.c += -fexceptions
 CFLAGS-getspent.c += -fexceptions
 CFLAGS-fgetspent.c += -fexceptions
-CFLAGS-fgetspent_r.c += -fexceptions $(libio-mtsafe)
-CFLAGS-putspent.c += -fexceptions $(libio-mtsafe)
+CFLAGS-fgetspent_r.c += -fexceptions
+CFLAGS-putspent.c += -fexceptions
 CFLAGS-getspnam.c += -fexceptions
 CFLAGS-getspnam_r.c += -fexceptions
 
diff --git a/stdio-common/Makefile b/stdio-common/Makefile
index a1603e82fe..ddeacb1342 100644
--- a/stdio-common/Makefile
+++ b/stdio-common/Makefile
@@ -357,8 +357,6 @@  CFLAGS-tst-gets.c += -Wno-deprecated-declarations
 # the fortified version had the same bug.
 CFLAGS-tst-bz11319-fortify2.c += -D_FORTIFY_SOURCE=2
 
-CPPFLAGS += $(libio-mtsafe)
-
 $(objpfx)tst-setvbuf1.out: /dev/null $(objpfx)tst-setvbuf1
 	$(test-program-cmd) > $@ 2>&1; \
 	$(evaluate-test)
diff --git a/stdio-common/vfprintf-internal.c b/stdio-common/vfprintf-internal.c
index 59bd76c890..b915803c66 100644
--- a/stdio-common/vfprintf-internal.c
+++ b/stdio-common/vfprintf-internal.c
@@ -2141,9 +2141,7 @@  struct helper_file
     struct _IO_wide_data _wide_data;
 #endif
     FILE *_put_stream;
-#ifdef _IO_MTSAFE_IO
     _IO_lock_t lock;
-#endif
   };
 
 static int
@@ -2251,9 +2249,7 @@  buffered_vfprintf (FILE *s, const CHAR_T *format, va_list args,
 #if _IO_JUMPS_OFFSET
   hp->_vtable_offset = 0;
 #endif
-#ifdef _IO_MTSAFE_IO
   hp->_lock = NULL;
-#endif
   hp->_flags2 = s->_flags2;
   _IO_JUMPS (&helper._f) = (struct _IO_jump_t *) &_IO_helper_jumps;
 
diff --git a/stdlib/Makefile b/stdlib/Makefile
index 60fc59c12c..1a10b18931 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -359,15 +359,6 @@  CFLAGS-system.c += -fexceptions
 CFLAGS-system.os = -fomit-frame-pointer
 CFLAGS-fmtmsg.c += -fexceptions
 
-CFLAGS-strfmon.c += $(libio-mtsafe)
-CFLAGS-strfmon_l.c += $(libio-mtsafe)
-
-# The strfrom class of functions call __printf_fp in order to convert the
-# floating-point value to characters.  This requires the value of IO_MTSAFE_IO.
-CFLAGS-strfromd.c += $(libio-mtsafe)
-CFLAGS-strfromf.c += $(libio-mtsafe)
-CFLAGS-strfroml.c += $(libio-mtsafe)
-
 CFLAGS-tst-bsearch.c += $(stack-align-test-flags)
 CFLAGS-tst-qsort.c += $(stack-align-test-flags)
 CFLAGS-tst-makecontext.c += -funwind-tables
diff --git a/stdlib/strfmon_l.c b/stdlib/strfmon_l.c
index d9b22088c7..e6fb378877 100644
--- a/stdlib/strfmon_l.c
+++ b/stdlib/strfmon_l.c
@@ -523,9 +523,7 @@  __vstrfmon_l_internal (char *s, size_t maxsize, locale_t loc,
 	  out_string (sign_string);
 
       /* Print the number.  */
-#ifdef _IO_MTSAFE_IO
       f._sbf._f._lock = NULL;
-#endif
       _IO_init_internal (&f._sbf._f, 0);
       _IO_JUMPS (&f._sbf) = &_IO_str_jumps;
       _IO_str_init_static_internal (&f, dest, (s + maxsize) - dest, dest);
diff --git a/stdlib/strfrom-skeleton.c b/stdlib/strfrom-skeleton.c
index 1fba04bf6a..0ccdd756cd 100644
--- a/stdlib/strfrom-skeleton.c
+++ b/stdlib/strfrom-skeleton.c
@@ -37,9 +37,7 @@  int
 STRFROM (char *dest, size_t size, const char *format, FLOAT f)
 {
   _IO_strnfile sfile;
-#ifdef _IO_MTSAFE_IO
   sfile.f._sbf._f._lock = NULL;
-#endif
 
   int done;
 
diff --git a/sysdeps/generic/stdio-lock.h b/sysdeps/generic/stdio-lock.h
index cfdaf82577..14cf458bdd 100644
--- a/sysdeps/generic/stdio-lock.h
+++ b/sysdeps/generic/stdio-lock.h
@@ -27,8 +27,8 @@  __libc_lock_define_recursive (typedef, _IO_lock_t)
 /* We need recursive (counting) mutexes.  */
 #ifdef _LIBC_LOCK_RECURSIVE_INITIALIZER
 # define _IO_lock_initializer _LIBC_LOCK_RECURSIVE_INITIALIZER
-#elif _IO_MTSAFE_IO
- #error libio needs recursive mutexes for _IO_MTSAFE_IO
+#else
+# error libio needs recursive mutexes
 #endif
 
 #define _IO_lock_init(_name)	__libc_lock_init_recursive (_name)
diff --git a/sysdeps/ieee754/float128/Makefile b/sysdeps/ieee754/float128/Makefile
index 571a841809..166e630290 100644
--- a/sysdeps/ieee754/float128/Makefile
+++ b/sysdeps/ieee754/float128/Makefile
@@ -1,10 +1,6 @@ 
 ifeq ($(subdir),stdlib)
 routines += float1282mpn strfromf128
 routines += strtof128 strtof128_l strtof128_nan mpn2float128
-
-# The strfrom class of functions call __printf_fp in order to convert the
-# floating-point value to characters.  This requires the value of IO_MTSAFE_IO.
-CFLAGS-strfromf128.c += $(libio-mtsafe)
 endif
 
 ifeq ($(subdir),wcsmbs)
diff --git a/sysdeps/nptl/libc-lock.h b/sysdeps/nptl/libc-lock.h
index 5af476c48b..c186375c31 100644
--- a/sysdeps/nptl/libc-lock.h
+++ b/sysdeps/nptl/libc-lock.h
@@ -25,7 +25,7 @@ 
 
 
 /* Mutex type.  */
-#if defined _LIBC || defined _IO_MTSAFE_IO
+#if defined _LIBC
 # if (!IS_IN (libc) && !IS_IN (libpthread)) || !defined _LIBC
 typedef struct { pthread_mutex_t mutex; } __libc_lock_recursive_t;
 # else
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index ca953804d0..b3bf4217a5 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -317,7 +317,6 @@  tests += tst-affinity tst-affinity-pid
 tests-static := tst-affinity-static
 tests += $(tests-static)
 
-CFLAGS-fork.c = $(libio-mtsafe)
 CFLAGS-getpid.o = -fomit-frame-pointer
 CFLAGS-getpid.os = -fomit-frame-pointer
 endif
diff --git a/wcsmbs/Makefile b/wcsmbs/Makefile
index df9a85f4a9..afb0610b55 100644
--- a/wcsmbs/Makefile
+++ b/wcsmbs/Makefile
@@ -103,8 +103,6 @@  CFLAGS-isoc99_fwscanf.c += -fexceptions
 CFLAGS-isoc99_vwscanf.c += -fexceptions
 CFLAGS-isoc99_vfwscanf.c += -fexceptions
 
-CPPFLAGS += $(libio-mtsafe)
-
 # We need to find the default version of strtold_l in stdlib.
 CPPFLAGS-wcstold_l.c += -I../stdlib