diff --git a/.gitignore b/.gitignore
index 93c2e54..042a1d8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -13,6 +13,7 @@ AUTHORS
 copyr-*
 copying.*
 glibc-*
+!glibc-var.h
 
 configparms
 
diff --git a/elf/Makefile b/elf/Makefile
index 9e07073..1811ac5 100644
--- a/elf/Makefile
+++ b/elf/Makefile
@@ -35,6 +35,7 @@ dl-routines	= $(addprefix dl-,load lookup object reloc deps hwcaps \
 ifeq (yes,$(use-ldconfig))
 dl-routines += dl-cache
 endif
+dl-routines += dl-glibc-var
 all-dl-routines = $(dl-routines) $(sysdep-dl-routines)
 # But they are absent from the shared libc, because that code is in ld.so.
 elide-routines.os = $(all-dl-routines) dl-support enbl-secure dl-origin \
diff --git a/elf/Versions b/elf/Versions
index 23deda9..3d34646 100644
--- a/elf/Versions
+++ b/elf/Versions
@@ -52,9 +52,11 @@ ld {
   }
   GLIBC_PRIVATE {
     # Those are in the dynamic linker, but used by libc.so.
+    __glibc_var_init;
     __libc_enable_secure;
     _dl_allocate_tls; _dl_allocate_tls_init;
     _dl_argv; _dl_find_dso_for_object; _dl_get_tls_static_info;
+    _dl_glibc_var;
     _dl_deallocate_tls; _dl_make_stack_executable; _dl_out_of_memory;
     _dl_rtld_di_serinfo; _dl_starting_up; _dl_tls_setup;
     _rtld_global; _rtld_global_ro;
diff --git a/elf/dl-environ.c b/elf/dl-environ.c
index afcd11d..dc907d8 100644
--- a/elf/dl-environ.c
+++ b/elf/dl-environ.c
@@ -22,10 +22,10 @@
 #include <ldsodefs.h>
 
 /* Walk through the environment of the process and return all entries
-   starting with `LD_'.  */
+   starting with `LD_' or 'GLIBC_'.  */
 char *
 internal_function
-_dl_next_ld_env_entry (char ***position)
+_dl_next_ld_env_entry (char ***position, char *first)
 {
   char **current = *position;
   char *result = NULL;
@@ -35,6 +35,7 @@ _dl_next_ld_env_entry (char ***position)
       if (__builtin_expect ((*current)[0] == 'L', 0)
 	  && (*current)[1] == 'D' && (*current)[2] == '_')
 	{
+	  *first = (*current)[0];
 	  result = &(*current)[3];
 
 	  /* Save current position for next visit.  */
@@ -43,6 +44,20 @@ _dl_next_ld_env_entry (char ***position)
 	  break;
 	}
 
+      if (__builtin_expect ((*current)[0] == 'G', 0)
+	  && (*current)[1] == 'L' && (*current)[2] == 'I'
+	  && (*current)[3] == 'B' && (*current)[4] == 'C'
+	  && (*current)[5] == '_')
+	{
+	  *first = (*current)[0];
+	  result = &(*current)[6];
+
+	  /* Save current position for next visit.  */
+	  *position = ++current;
+
+	  break;
+	}
+
       ++current;
     }
 
diff --git a/elf/dl-glibc-var.c b/elf/dl-glibc-var.c
new file mode 100644
index 0000000..2a19bea
--- /dev/null
+++ b/elf/dl-glibc-var.c
@@ -0,0 +1,110 @@
+/* Fast access to GLIBC_* environment variables, without having to walk
+   the environment multiple times.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <string.h>
+#include <glibc-var.h>
+
+#define _GLIBC_VAR_ENTRY(a) [GLIBC_VAR_##a] = { #a, sizeof(#a) - 1, NULL }
+
+struct glibc_var _dl_glibc_var[] =
+{
+  _GLIBC_VAR_ENTRY(PTHREAD_MUTEX),
+  _GLIBC_VAR_ENTRY(PTHREAD_RWLOCK),
+  /* Add more GLIBC_ variables here.  */
+  /* Make the names as long as possible to pass code review.  */
+  [GLIBC_VAR_MAX] =    { NULL, 0, NULL }
+};
+
+internal_function void
+__record_glibc_var (char *name, int len, char *val)
+{
+  int i;
+
+  for (i = 0; i < GLIBC_VAR_MAX; i++)
+    {
+      struct glibc_var *v = &_dl_glibc_var[i];
+
+      if (len == v->len && memcmp (v->name, name, v->len) == 0)
+	{
+	  v->val = val;
+	  break;
+	}
+    }
+  /* Ignore unknown GLIBC_ variables.  */
+}
+
+#ifndef SHARED
+
+/* If SHARED the env walk is shared with rtld.c.  */
+
+static char *
+next_env_entry (char first, char ***position)
+{
+  char **current = *position;
+  char *result = NULL;
+
+  while (*current != NULL)
+    {
+      if ((*current)[0] == first)
+	{
+	  result = *current;
+	  *position = ++current;
+	  break;
+	}
+
+      ++current;
+    }
+
+  return result;
+}
+
+/* May be called from libpthread.  */
+
+void
+__glibc_var_init (int argc __attribute__ ((unused)),
+		  char **argv  __attribute__ ((unused)),
+		  char **environ)
+{
+  char *envline;
+  static int initialized;
+
+  if (initialized != 0)
+    return;
+  initialized = 1;
+
+  while ((envline = next_env_entry ('G', &environ)) != NULL)
+    {
+      if (envline[1] == 'L' && envline[2] == 'I' && envline[3] == 'B'
+	  && envline[4] == 'C' && envline[5] == '_')
+	{
+	  char *e = envline + 6;
+	  while (*e && *e != '=')
+	    e++;
+	  if (*e == 0)
+	    continue;
+	  __record_glibc_var (envline + 6, e - (envline + 6), e + 1);
+	}
+    }
+}
+
+void (*const __glibc_var_init_array []) (int, char **, char **)
+  __attribute__ ((section (".preinit_array"), aligned (sizeof (void *)))) =
+{
+  &__glibc_var_init
+};
+#endif
diff --git a/elf/rtld.c b/elf/rtld.c
index fb02ecd..a5c1aa2 100644
--- a/elf/rtld.c
+++ b/elf/rtld.c
@@ -41,6 +41,7 @@
 #include <tls.h>
 #include <stap-probe.h>
 #include <stackinfo.h>
+#include <glibc-var.h>
 
 #include <assert.h>
 
@@ -2338,7 +2339,9 @@ process_dl_audit (char *str)
 
 /* Process all environments variables the dynamic linker must recognize.
    Since all of them start with `LD_' we are a bit smarter while finding
-   all the entries.  */
+   all the entries.  In addition we also save a bunch of GLIBC_ variables
+   used by other parts of glibc, so that each startup only has to walk the
+   environment once.  */
 extern char **_environ attribute_hidden;
 
 
@@ -2349,12 +2352,13 @@ process_envvars (enum mode *modep)
   char *envline;
   enum mode mode = normal;
   char *debug_output = NULL;
+  char first;
 
   /* This is the default place for profiling data file.  */
   GLRO(dl_profile_output)
     = &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
 
-  while ((envline = _dl_next_ld_env_entry (&runp)) != NULL)
+  while ((envline = _dl_next_ld_env_entry (&runp, &first)) != NULL)
     {
       size_t len = 0;
 
@@ -2367,6 +2371,15 @@ process_envvars (enum mode *modep)
 	   invalid memory below.  */
 	continue;
 
+      /* Must be for GLIBC_ */
+      if (first == 'G')
+	{
+	  __record_glibc_var (envline, len, envline + len + 1);
+	  continue;
+	}
+
+      /* Must be for LD_ */
+
       switch (len)
 	{
 	case 4:
diff --git a/include/glibc-var.h b/include/glibc-var.h
new file mode 100644
index 0000000..c9b2f21
--- /dev/null
+++ b/include/glibc-var.h
@@ -0,0 +1,49 @@
+/* Fast access to GLIBC_* environment variables, without having to walk
+   the environment. Register new ones in in elf/glibc-var.c
+   Copyright (C) 2013 Free Software Foundation, Inc.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifndef _GLIBC_VAR_H
+# define _GLIBC_VAR_H 1
+
+# include <libc-symbols.h>
+
+enum
+{
+ GLIBC_VAR_PTHREAD_MUTEX,
+ GLIBC_VAR_PTHREAD_RWLOCK,
+ GLIBC_VAR_MAX
+};
+
+struct glibc_var
+{
+  const char *name;
+  int len;
+  char *val;
+};
+
+extern struct glibc_var _dl_glibc_var[];
+extern void __record_glibc_var (char *name, int len, char *val) internal_function;
+
+/* Call this if you're in a constructor that may run before glibc-var's.  */
+# ifndef SHARED
+extern void __glibc_var_init (int ac, char **av, char **env);
+# else
+/* For shared this is always done in the dynamic linker early enough.  */
+# define __glibc_var_init(a,b,c) do {} while (0)
+# endif
+
+#endif
diff --git a/sysdeps/generic/ldsodefs.h b/sysdeps/generic/ldsodefs.h
index d07eaac..b8bd98c 100644
--- a/sysdeps/generic/ldsodefs.h
+++ b/sysdeps/generic/ldsodefs.h
@@ -893,9 +893,9 @@ extern void _dl_mcount_wrapper (void *selfpc);
 /* Show the members of the auxiliary array passed up from the kernel.  */
 extern void _dl_show_auxv (void) internal_function;
 
-/* Return all environment variables starting with `LD_', one after the
-   other.  */
-extern char *_dl_next_ld_env_entry (char ***position) internal_function;
+/* Return all environment variables starting with `LD_' or `GLIBC_', one
+   after the other.  */
+extern char *_dl_next_ld_env_entry (char ***position, char *first) internal_function;
 
 /* Return an array with the names of the important hardware capabilities.  */
 extern const struct r_strlenpair *_dl_important_hwcaps (const char *platform,
