diff --git a/runtime/arch/arm/thread_arm.cc b/runtime/arch/arm/thread_arm.cc
index 8c1efeb..df4a04a 100644
--- a/runtime/arch/arm/thread_arm.cc
+++ b/runtime/arch/arm/thread_arm.cc
@@ -28,4 +28,8 @@
   CHECK_EQ(THREAD_ID_OFFSET, OFFSETOF_MEMBER(Thread, thin_lock_thread_id_));
 }
 
+void Thread::CleanupCpu() {
+  // Do nothing.
+}
+
 }  // namespace art
diff --git a/runtime/arch/mips/thread_mips.cc b/runtime/arch/mips/thread_mips.cc
index bd54549..f5d211f 100644
--- a/runtime/arch/mips/thread_mips.cc
+++ b/runtime/arch/mips/thread_mips.cc
@@ -27,4 +27,8 @@
   CHECK_EQ(THREAD_EXCEPTION_OFFSET, OFFSETOF_MEMBER(Thread, exception_));
 }
 
+void Thread::CleanupCpu() {
+  // Do nothing.
+}
+
 }  // namespace art
diff --git a/runtime/arch/x86/thread_x86.cc b/runtime/arch/x86/thread_x86.cc
index 39bad58..235da99 100644
--- a/runtime/arch/x86/thread_x86.cc
+++ b/runtime/arch/x86/thread_x86.cc
@@ -40,8 +40,9 @@
 
 namespace art {
 
+static Mutex modify_ldt_lock("modify_ldt lock");
+
 void Thread::InitCpu() {
-  static Mutex modify_ldt_lock("modify_ldt lock");
   MutexLock mu(Thread::Current(), modify_ldt_lock);
 
   const uintptr_t base = reinterpret_cast<uintptr_t>(this);
@@ -113,7 +114,6 @@
   uint16_t table_indicator = 1 << 2;  // LDT
   uint16_t rpl = 3;  // Requested privilege level
   uint16_t selector = (entry_number << 3) | table_indicator | rpl;
-  // TODO: use our assembler to generate code
   __asm__ __volatile__("movw %w0, %%fs"
       :    // output
       : "q"(selector)  // input
@@ -124,7 +124,6 @@
 
   // Sanity check that reads from %fs point to this Thread*.
   Thread* self_check;
-  // TODO: use our assembler to generate code
   CHECK_EQ(THREAD_SELF_OFFSET, OFFSETOF_MEMBER(Thread, self_));
   __asm__ __volatile__("movl %%fs:(%1), %0"
       : "=r"(self_check)  // output
@@ -138,4 +137,36 @@
   CHECK_EQ(THREAD_ID_OFFSET, OFFSETOF_MEMBER(Thread, thin_lock_thread_id_));
 }
 
+void Thread::CleanupCpu() {
+  MutexLock mu(Thread::Current(), modify_ldt_lock);
+
+  // Sanity check that reads from %fs point to this Thread*.
+  Thread* self_check;
+  __asm__ __volatile__("movl %%fs:(%1), %0"
+      : "=r"(self_check)  // output
+      : "r"(THREAD_SELF_OFFSET)  // input
+      :);  // clobber
+  CHECK_EQ(self_check, this);
+
+  // Extract the LDT entry number from the FS register.
+  uint16_t selector;
+  __asm__ __volatile__("movw %%fs, %w0"
+      : "=q"(selector)  // output
+      :  // input
+      :);  // clobber
+
+  // Free LDT entry.
+#if defined(__APPLE__)
+  i386_set_ldt(selector >> 3, 0, 1);
+#else
+  user_desc ldt_entry;
+  memset(&ldt_entry, 0, sizeof(ldt_entry));
+  ldt_entry.entry_number = selector >> 3;
+  ldt_entry.contents = MODIFY_LDT_CONTENTS_DATA;
+  ldt_entry.seg_not_present = 1;
+
+  syscall(__NR_modify_ldt, 1, &ldt_entry, sizeof(ldt_entry));
+#endif
+}
+
 }  // namespace art
diff --git a/runtime/thread.cc b/runtime/thread.cc
index 68f3c04..c3ef228 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -1046,9 +1046,11 @@
   }
   opeer_ = nullptr;
 
-  delete jni_env_;
-  jni_env_ = nullptr;
-
+  bool initialized = (jni_env_ != nullptr);  // Did Thread::Init run?
+  if (initialized) {
+    delete jni_env_;
+    jni_env_ = nullptr;
+  }
   CHECK_NE(GetState(), kRunnable);
   CHECK_NE(ReadFlag(kCheckpointRequest), true);
   CHECK(checkpoint_functions_[0] == nullptr);
@@ -1065,6 +1067,10 @@
     delete long_jump_context_;
   }
 
+  if (initialized) {
+    CleanupCpu();
+  }
+
   delete debug_invoke_req_;
   delete single_step_control_;
   delete instrumentation_stack_;
diff --git a/runtime/thread.h b/runtime/thread.h
index 0810909..4a37ca0 100644
--- a/runtime/thread.h
+++ b/runtime/thread.h
@@ -619,6 +619,7 @@
   void Init(ThreadList*, JavaVMExt*) EXCLUSIVE_LOCKS_REQUIRED(Locks::runtime_shutdown_lock_);
   void InitCardTable();
   void InitCpu();
+  void CleanupCpu();
   void InitTlsEntryPoints();
   void InitTid();
   void InitPthreadKeySelf();