diff --git a/libc/private/ErrnoRestorer.h b/libc/private/ErrnoRestorer.h
new file mode 100644
index 0000000..ed6ab62
--- /dev/null
+++ b/libc/private/ErrnoRestorer.h
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ERRNO_RESTORER_H
+#define ERRNO_RESTORER_H
+
+#include <errno.h>
+
+class ErrnoRestorer {
+ public:
+  explicit ErrnoRestorer() : saved_errno_(errno) {
+  }
+
+  ~ErrnoRestorer() {
+    errno = saved_errno_;
+  }
+
+  void override(int new_errno) {
+    saved_errno_ = new_errno;
+  }
+
+ private:
+  int saved_errno_;
+
+  // Disallow copy and assignment.
+  ErrnoRestorer(const ErrnoRestorer&);
+  void operator=(const ErrnoRestorer&);
+};
+
+#endif // ERRNO_RESTORER_H
diff --git a/libc/private/ThreadLocalBuffer.h b/libc/private/ThreadLocalBuffer.h
index 1c5e3f4..e5bd28c 100644
--- a/libc/private/ThreadLocalBuffer.h
+++ b/libc/private/ThreadLocalBuffer.h
@@ -36,19 +36,20 @@
 // so we make do with macros instead of a C++ class.
 // TODO: move __cxa_guard_acquire and __cxa_guard_release into libc.
 
+// We used to use pthread_once to initialize the keys, but life is more predictable
+// if we allocate them all up front when the C library starts up, via __constructor__.
+
 #define GLOBAL_INIT_THREAD_LOCAL_BUFFER(name) \
-  static pthread_once_t __bionic_tls_ ## name ## _once; \
   static pthread_key_t __bionic_tls_ ## name ## _key; \
   static void __bionic_tls_ ## name ## _key_destroy(void* buffer) { \
     free(buffer); \
   } \
-  static void __bionic_tls_ ## name ## _key_init() { \
+  __attribute__((constructor)) static void __bionic_tls_ ## name ## _key_init() { \
     pthread_key_create(&__bionic_tls_ ## name ## _key, __bionic_tls_ ## name ## _key_destroy); \
   }
 
 // Leaves "name_tls_buffer" and "name_tls_buffer_size" defined and initialized.
 #define LOCAL_INIT_THREAD_LOCAL_BUFFER(type, name, byte_count) \
-  pthread_once(&__bionic_tls_ ## name ## _once, __bionic_tls_ ## name ## _key_init); \
   type name ## _tls_buffer = \
       reinterpret_cast<type>(pthread_getspecific(__bionic_tls_ ## name ## _key)); \
   if (name ## _tls_buffer == NULL) { \
diff --git a/libc/private/bionic_futex.h b/libc/private/bionic_futex.h
index eb49fb7..6c7fdbe 100644
--- a/libc/private/bionic_futex.h
+++ b/libc/private/bionic_futex.h
@@ -30,6 +30,8 @@
 
 #include <linux/futex.h>
 
+__BEGIN_DECLS
+
 extern int __futex_wait(volatile void *ftx, int val, const struct timespec *timeout);
 extern int __futex_wake(volatile void *ftx, int count);
 
@@ -54,4 +56,6 @@
 extern int  __futex_wake_ex(volatile void *ftx, int pshared, int val);
 extern int  __futex_wait_ex(volatile void *ftx, int pshared, int val, const struct timespec *timeout);
 
+__END_DECLS
+
 #endif /* _BIONIC_FUTEX_H */
diff --git a/libc/private/bionic_tls.h b/libc/private/bionic_tls.h
index edf878f..4dd66c0 100644
--- a/libc/private/bionic_tls.h
+++ b/libc/private/bionic_tls.h
@@ -43,28 +43,40 @@
  ** pre-allocated slot directly for performance reason).
  **/
 
-/* Maximum number of elements in the TLS array. */
-#define BIONIC_TLS_SLOTS            64
-
 /* Well-known TLS slots. What data goes in which slot is arbitrary unless otherwise noted. */
 enum {
   TLS_SLOT_SELF = 0, /* The kernel requires this specific slot for x86. */
   TLS_SLOT_THREAD_ID,
   TLS_SLOT_ERRNO,
+
+  /* These two aren't used by bionic itself, but allow the graphics code to
+   * access TLS directly rather than using the pthread API. */
   TLS_SLOT_OPENGL_API = 3,
   TLS_SLOT_OPENGL = 4,
+
+  /* This slot is only used to pass information from the dynamic linker to
+   * libc.so when the C library is loaded in to memory. The C runtime init
+   * function will then clear it. Since its use is extremely temporary,
+   * we reuse an existing location that isn't needed during libc startup. */
+  TLS_SLOT_BIONIC_PREINIT = TLS_SLOT_OPENGL_API,
+
   TLS_SLOT_STACK_GUARD = 5, /* GCC requires this specific slot for x86. */
   TLS_SLOT_DLERROR,
 
   TLS_SLOT_FIRST_USER_SLOT /* Must come last! */
 };
 
-/* This slot is only used to pass information from the dynamic linker to
- * libc.so when the C library is loaded in to memory. The C runtime init
- * function will then clear it. Since its use is extremely temporary,
- * we reuse an existing location that isn't needed during libc startup.
+/*
+ * Maximum number of elements in the TLS array.
+ * POSIX says this must be at least 128, but Android has traditionally had only 64, minus those
+ * ones used internally by bionic itself.
+ * There are two kinds of slot used internally by bionic --- there are the well-known slots
+ * enumerated above, and then there are those that are allocated during startup by calls to
+ * pthread_key_create; grep for GLOBAL_INIT_THREAD_LOCAL_BUFFER to find those. We need to manually
+ * maintain that second number, but pthread_test will fail if we forget.
  */
-#define  TLS_SLOT_BIONIC_PREINIT    TLS_SLOT_OPENGL_API
+#define GLOBAL_INIT_THREAD_LOCAL_BUFFER_COUNT 4
+#define BIONIC_TLS_SLOTS 64
 
 /* set the Thread Local Storage, must contain at least BIONIC_TLS_SLOTS pointers */
 extern void __init_tls(void**  tls, void*  thread_info);