diff --git a/src/thread/thread.c b/src/thread/thread.c
index 0e1c9fe..bda3397 100644
--- a/src/thread/thread.c
+++ b/src/thread/thread.c
@@ -1,3 +1,4 @@
+#include <string.h>
 #ifndef USE_PTHREAD
 
 #include "thread.h"
@@ -9,19 +10,21 @@
 #include <ucontext.h>
 #include <valgrind/valgrind.h>
 
+#define FINISHED  0x1
+#define ALLOCATED 0x2
+
 #ifndef STACK_SIZE
 #define STACK_SIZE 4096*4
 #endif
 
 struct context_entry {
+  TAILQ_ENTRY(context_entry) link;
   ucontext_t context;
   thread_t id;
   thread_t parent;
-  int was_allocated;
-  int finished;
   void *retvalue;
   int valgrind_id;
-  TAILQ_ENTRY(context_entry) link;
+  char status;
 };
 
 static TAILQ_HEAD(context_head, context_entry) head = TAILQ_HEAD_INITIALIZER(head);
@@ -33,17 +36,21 @@ int thread_yield(void) {
     return 0;
   }
   struct context_entry *first;
+  int count = 0;
   do  {
+    if (count++ == counter) {
+      return 0;
+    }
     first = TAILQ_FIRST(&head);
     if (!first) {
       return -1;
     }
+    TAILQ_REMOVE(&head, first, link);
+    TAILQ_INSERT_TAIL(&head, first, link);
     if (first->id == running->id) {
       return 0;
     }
-    TAILQ_REMOVE(&head, first, link);
-    TAILQ_INSERT_TAIL(&head, first, link);
-  } while (first->finished);
+  } while (first->status & FINISHED);
   struct context_entry *old_runner = running;
   running = first;
   swapcontext(&old_runner->context, &running->context);
@@ -61,17 +68,18 @@ int thread_create(thread_t *newthread, void *(*func)(void *), void *funcarg) {
   TRACE("Create a new thread that execute function %p", func);
   if (counter == 0) {
     struct context_entry *main = malloc(sizeof(*main));
+    memset(main, 0, sizeof(*main));
     getcontext(&main->context);
     main->id = 0;
     main->parent = 0;
-    main->finished = 0;
+    main->status = 0;
     main->retvalue = 0;
-    main->was_allocated = 0;
     TAILQ_INSERT_HEAD(&head, main, link);
     running = main;
     counter++;
   }
   struct context_entry *new_entry = malloc(sizeof(*new_entry));
+  memset(new_entry, 0, sizeof(*new_entry));
   getcontext(&new_entry->context);
   new_entry->context.uc_stack.ss_sp = malloc(STACK_SIZE);
   new_entry->context.uc_stack.ss_size = STACK_SIZE;
@@ -81,9 +89,8 @@ int thread_create(thread_t *newthread, void *(*func)(void *), void *funcarg) {
     );
   new_entry->id = new_entry;
   new_entry->parent = running->id;
-  new_entry->finished = 0;
+  new_entry->status = ALLOCATED;
   new_entry->retvalue = 0;
-  new_entry->was_allocated = 1;
   *newthread = new_entry;
   makecontext(&new_entry->context, (void (*)()) func, 1, funcarg);
   counter++;
@@ -92,7 +99,7 @@ int thread_create(thread_t *newthread, void *(*func)(void *), void *funcarg) {
 }
 
 void print_entry(struct context_entry *entry) {
-  TRACE("CONTEXT (%p, %p, %d, %p);\n", entry, entry->id, entry->finished, entry->parent);
+  TRACE("CONTEXT (%p, %p, %d, %p);\n", entry, entry->id, (entry->status & FINISHED) > 0, entry->parent);
 }
 
 int thread_join(thread_t thread, void **retval) {
@@ -102,20 +109,27 @@ int thread_join(thread_t thread, void **retval) {
     if (entry->id != thread) {
       continue;
     }
-    while (!entry->finished) {
+    TRACE("FIND");
+    print_entry(entry);
+    while (!entry->status & FINISHED) {
+      TRACE("NOT FINISHED");
       thread_yield();
     }
+    TRACE("AFTER");
     if (retval)
       *retval = entry->retvalue;
     TAILQ_REMOVE(&head, entry, link);
-    if (entry->was_allocated) {
+    if (entry->status & ALLOCATED) {
+      TRACE("FREE\n");
       VALGRIND_STACK_DEREGISTER(entry->valgrind_id);
       free(entry->context.uc_stack.ss_sp);
+    } else {
+      TRACE("NOT ALLOCATED\n");
     }
     free(entry);
     if (--counter == 1) {
       TAILQ_REMOVE(&head, running, link);
-      if (running->was_allocated) {
+      if (running->status & ALLOCATED) {
         VALGRIND_STACK_DEREGISTER(running->valgrind_id);
         free(running->context.uc_stack.ss_sp);
       }
@@ -130,7 +144,7 @@ int thread_join(thread_t thread, void **retval) {
 
 void thread_exit(void *retval) {
   TRACE("Exit thread %p", running);
-  running->finished = 1;
+  running->status |= FINISHED;
   running->retvalue = retval;
   thread_yield();
 }