[Zion] Don't try to set state on dying threads in cleanup.

.gitignore

@@ -1,6 +1,7 @@
 builddbg/
 test-bin/
 __pycache__/
+.ccls-cache/
 compile_commands.json
 
 sysroot/bin

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.2)
+cmake_minimum_required(VERSION 3.5)
 
 # Set because our cross compiler can't do dynamic linking?
 set(CMAKE_TRY_COMPILE_TARGET_TYPE "STATIC_LIBRARY")

zion/object/thread.cpp

@@ -120,8 +120,10 @@ void Thread::Cleanup() {
   // 2. Unblock waiting threads.
   while (blocked_threads_.size() != 0) {
     auto thread = blocked_threads_.PopFront();
-    thread->SetState(Thread::RUNNABLE);
-    gScheduler->Enqueue(thread);
+    if (!thread->IsDying()) {
+      thread->SetState(Thread::RUNNABLE);
+      gScheduler->Enqueue(thread);
+    }
   }
 
   // 3. Release Kernel Stack