diff --git a/include/arch/mr_hw_stack.h b/include/arch/mr_hw_stack.h
deleted file mode 100644
index a024eed..0000000
--- a/include/arch/mr_hw_stack.h
+++ /dev/null
@@ -1,50 +0,0 @@
-/**
- * @copyright (c) 2024, MacRsh
- *
- * @license SPDX-License-Identifier: Apache-2.0
- *
- * @date 2024-09-06        MacRsh        First version
- */
-
-#ifndef __MR_HW_STACK_H__
-#define __MR_HW_STACK_H__
-
-#ifdef __cplusplus
-"C" {
-#endif /* __cplusplus */
-
-/**
- * @addtogroup Stack hardware interface
- * @{
- */
-
-/**
- * @brief This function initialize the hardware stack.
- * @param entry The entry point.
- * @param stack_addr The stack address(top).
- * @return The top of the stack.
- */
- void *mr_hw_stack_init(void *entry, void *stack_addr);
-
-/**
- * @brief This function switch the hardware stack.
- *
- * @param from The old stack address(top).
- * @param to The new stack address(top).
- */
-void mr_hw_context_switch(void *from, void *to);
-
-/**
- * @brief This function switch the hardware stack.
- *
- * @param to The new stack address(top).
- */
-void mr_hw_context_switch_to(void *to);
-
-/** @} */
-
-#ifdef __cplusplus
-}
-#endif /* __cplusplus */
-
-#endif /* __MR_HW_STACK_H__ */
diff --git a/include/kernel/kos/mr_kos.h b/include/kernel/kos/mr_kos.h
index 981888e..6bd4966 100644
--- a/include/kernel/kos/mr_kos.h
+++ b/include/kernel/kos/mr_kos.h
@@ -54,23 +54,37 @@ typedef struct mr_kos {
 } mr_kos_t;
 
 /**
- * @brief This function registers kernel os.
+ * @brief This function registers a kernel os.
  *
  * @return 0 on success, or a negative error code on failure.
  */
-mr_err_t mr_kos_register(mr_kos_type_t *type);
+mr_err_t mr_kos_register(mr_kos_type_t *ktype);
 
 /**
- * @brief This function gets kernel os.
+ * @brief This function gets a kernel os.
+ *
+ * @param kos The kernel os.
+ * @return The kernel os on success, or MR_NULL on failure.
+ */
+MR_INLINE mr_kos_t *mr_kos_get(mr_kos_t *kos) {
+    return (mr_kos_t *)mr_kobject_get((mr_kobject_t *)kos);
+}
+
+/**
+ * @brief This function puts a kernel os.
+ *
+ * @param kos The kernel os.
+ */
+MR_INLINE void mr_kos_put(mr_kos_t *kos) {
+    mr_kobject_put((mr_kobject_t *)kos);
+}
+
+/**
+ * @brief This function finds a kernel os.
  *
  * @return The kernel os.
  */
-mr_kos_t *mr_kos_get(void);
-
-/**
- * @brief This function puts kernel os.
- */
-void mr_kos_put(void);
+mr_kos_t *mr_kos_find(void);
 
 /**
  * @brief This macro function gets the kthread operations of a kernel os.
diff --git a/include/kernel/kos/mr_kthread.h b/include/kernel/kos/mr_kthread.h
index d42d2d8..f00c1b6 100644
--- a/include/kernel/kos/mr_kthread.h
+++ b/include/kernel/kos/mr_kthread.h
@@ -144,6 +144,25 @@ mr_err_t mr_kthread_exit(mr_kthread_t *kth);
  */
 mr_kthread_t *mr_kthread_self(void);
 
+/**
+ * @brief This function get a kthread.
+ *
+ * @param kth The kthread.
+ * @return The kthread on success, or MR_NULL on failure.
+ */
+MR_INLINE mr_kthread_t *mr_kthread_get(mr_kthread_t *kth) {
+    return (mr_kthread_t *)mr_kobject_get((mr_kobject_t *)kth);
+}
+
+/**
+ * @brief This function put a kthread.
+ *
+ * @param kth The kthread.
+ */
+MR_INLINE void mr_kthread_put(mr_kthread_t *kth) {
+    mr_kobject_put((mr_kobject_t *)kth);
+}
+
 /**
  * @brief This function find a kthread.
  *
diff --git a/include/mr_config.h b/include/mr_config.h
index 64378b9..a7f824f 100644
--- a/include/mr_config.h
+++ b/include/mr_config.h
@@ -5,6 +5,7 @@
 extern "C" {
 #endif /* __cplusplus */
 
+#define MR_USE_LIBC_PRINTF
 
 #ifdef __cplusplus
 }
diff --git a/kernel/kos/kos.c b/kernel/kos/kos.c
index 3251ac9..9a85c66 100644
--- a/kernel/kos/kos.c
+++ b/kernel/kos/kos.c
@@ -8,41 +8,36 @@
 
 #include <kernel/kos/mr_kos.h>
 
-static mr_kos_t kos;
+static mr_kos_t kroot;
 
-MR_INLINE void kos_init(mr_kos_t *os, mr_kos_type_t *type) {
+MR_INLINE void kos_init(mr_kos_t *os, mr_kos_type_t *ktype) {
     /* Init kos */
-    os->type = type;
+    os->type = ktype;
 }
 
-MR_INLINE mr_err_t kos_init_register(mr_kos_t *os, const char *name,
-                                     mr_kos_type_t *type) {
+MR_INLINE mr_err_t kos_init_register(mr_kos_t *kos, const char *name,
+                                     mr_kos_type_t *ktype) {
     /* Init kos */
-    kos_init(os, type);
+    kos_init(kos, ktype);
 
     /* Init kset */
-    mr_kset_init((mr_kset_t *)os, MR_NULL);
+    mr_kset_init((mr_kset_t *)kos, MR_NULL);
 
     /* Register kset */
-    return mr_kset_register((mr_kset_t *)os, name);
+    return mr_kset_register((mr_kset_t *)kos, name);
 }
 
 mr_err_t mr_kos_register(mr_kos_type_t *type) {
     /* Check arguments */
-    if (MR_KOBJECT_IS_INITED(&kos) || (!type)) {
+    if (MR_KOBJECT_IS_INITED(&kroot) || (!type)) {
         return -MR_EINVAL;
     }
 
     /* Init and register kos */
-    return kos_init_register(&kos, "os", type);
+    return kos_init_register(&kroot, "os", type);
 }
 
-mr_kos_t *mr_kos_get(void) {
-    /* Get kos */
-    return (mr_kos_t *)mr_kobject_get((mr_kobject_t *)&kos);
-}
-
-void mr_kos_put(void) {
-    /* Put kos */
-    mr_kobject_put((mr_kobject_t *)&kos);
+mr_kos_t *mr_kos_find(void) {
+    /* Find kos in kroot */
+    return &kroot;
 }
diff --git a/kernel/kos/kthread.c b/kernel/kos/kthread.c
index 7ee129c..2d78424 100644
--- a/kernel/kos/kthread.c
+++ b/kernel/kos/kthread.c
@@ -34,6 +34,20 @@ MR_INLINE mr_err_t kthread_res_alloc(mr_kthread_t *kth, mr_size_t size) {
     return 0;
 }
 
+MR_INLINE void kthread_res_free(mr_kthread_t *kth) {
+    const void *res;
+
+    /* If resource is inline or takeover, not need to free */
+    res = ((kth->res != kth->ires) && (kth->entry)) ? kth->res : MR_NULL;
+    if (res) {
+        mr_free((void *)res);
+    }
+}
+
+MR_INLINE mr_bool_t kthread_is_takeover(mr_kthread_t *kth) {
+    return (kth->res != kth->ires) && (!kth->entry);
+}
+
 MR_INLINE mr_err_t kthread_init(mr_kthread_t *kth, const char *name,
                                 mr_ptr_t entry, mr_ptr_t args, void *stack,
                                 mr_size_t stack_size, mr_uint32_t priority,
@@ -47,30 +61,38 @@ MR_INLINE mr_err_t kthread_init(mr_kthread_t *kth, const char *name,
         return -MR_EINVAL;
     }
 
+    /* Non-takeover kthread need to initialize resources */
+    if (!kthread_is_takeover(kth)) {
+        /* Alloc resource */
+        ret = kthread_res_alloc(kth, type->size);
+        if (ret != 0) {
+            return ret;
+        }
+
+        /* Init kthread resource */
+        ret = MR_KOS_KTH_OPS(kos)->init((void *)kth->res, name, kth, stack,
+                                        stack_size, priority, tick);
+        if (ret != 0) {
+            kthread_res_free(kth);
+            return ret;
+        }
+    }
+
     /* Init kthread */
     kth->priority = priority;
     kth->tick = tick;
     kth->entry = entry;
     kth->args = args;
-    kth->os = kos;
-
-    /* Takeover kthread resources not need init. */
-    if (!kth->entry) {
-        return 0;
-    }
-
-    /* Alloc resource */
-    ret = kthread_res_alloc(kth, type->size);
-    if (ret != 0) {
-        return ret;
-    }
-
-    /* Init kthread resource */
-    return MR_KOS_KTH_OPS(kth->os)->init((void *)kth->res, name, kth, stack,
-                                         stack_size, priority, tick);
+    kth->os = mr_kos_get(kos);
+    return 0;
 }
 
 MR_INLINE mr_err_t kthread_del(mr_kthread_t *kth) {
+    /* Takeover kthread do not need to delete */
+    if (kthread_is_takeover(kth)) {
+        return 0;
+    }
+
     /* Delete kthread resource */
     return MR_KOS_KTH_OPS(kth->os)->del((void *)kth->res);
 }
@@ -84,7 +106,7 @@ MR_INLINE mr_err_t kthread_init_add(mr_kthread_t *kth, mr_ktype_t *ktype,
     mr_err_t ret;
 
     /* Get kos */
-    kos = mr_kos_get();
+    kos = mr_kos_get(mr_kos_find());
     if (!kos) {
         return -MR_ENOSYS;
     }
@@ -102,13 +124,15 @@ MR_INLINE mr_err_t kthread_init_add(mr_kthread_t *kth, mr_ktype_t *ktype,
     /* Add kobject to kroot */
     ret = mr_kobject_add((mr_kobject_t *)kth, (mr_kobject_t *)&kroot, name);
     if (ret != 0) {
+        mr_kos_put(kos);
         kthread_del(kth);
+        kthread_res_free(kth);
         goto _exit;
     }
 
 _exit:
     /* Put kos */
-    mr_kos_put();
+    mr_kos_put(kos);
     return ret;
 }
 
@@ -200,11 +224,20 @@ mr_err_t mr_kthread_del(mr_kthread_t *kth) {
 }
 
 MR_INLINE mr_err_t kthread_startup(mr_kthread_t *kth) {
-    /* Get kobject */
-    mr_kobject_get((mr_kobject_t *)kth);
+    mr_err_t ret;
+
+    /* Prevents run-time release(exit and cleanup) */
+    mr_kthread_get(kth);
+    mr_kthread_get(kth);
 
     /* Startup kthread resource */
-    return MR_KOS_KTH_OPS(kth->os)->startup((void *)kth->res);
+    ret = MR_KOS_KTH_OPS(kth->os)->startup((void *)kth->res);
+    if (ret != 0) {
+        mr_kthread_put(kth);
+        mr_kthread_put(kth);
+        return ret;
+    }
+    return 0;
 }
 
 mr_err_t mr_kthread_startup(mr_kthread_t *kth) {
@@ -237,7 +270,7 @@ MR_INLINE mr_err_t kthread_yield(void) {
     mr_err_t ret;
 
     /* Get kos */
-    kos = mr_kos_get();
+    kos = mr_kos_get(mr_kos_find());
     if (!kos) {
         return -MR_ENOSYS;
     }
@@ -246,7 +279,7 @@ MR_INLINE mr_err_t kthread_yield(void) {
     ret = MR_KOS_KTH_OPS(kos)->yield();
 
     /* Put kos */
-    mr_kos_put();
+    mr_kos_put(kos);
     return ret;
 }
 
@@ -275,7 +308,7 @@ MR_INLINE mr_err_t kthread_sleep(mr_tick_t tick) {
     mr_err_t ret;
 
     /* Get kos */
-    kos = mr_kos_get();
+    kos = mr_kos_get(mr_kos_find());
     if (!kos) {
         return -MR_ENOSYS;
     }
@@ -284,7 +317,7 @@ MR_INLINE mr_err_t kthread_sleep(mr_tick_t tick) {
     ret = MR_KOS_KTH_OPS(kos)->sleep(tick);
 
     /* Put kos */
-    mr_kos_put();
+    mr_kos_put(kos);
     return ret;
 }
 
@@ -294,8 +327,17 @@ mr_err_t mr_kthread_sleep(mr_tick_t tick) {
 }
 
 MR_INLINE mr_err_t kthread_exit(mr_kthread_t *kth) {
+    mr_err_t ret;
+
     /* Exit kthread resource */
-    return MR_KOS_KTH_OPS(kth->os)->exit((void *)kth->res);
+    ret = MR_KOS_KTH_OPS(kth->os)->exit((void *)kth->res);
+    if (ret != 0) {
+        return ret;
+    }
+
+    /* Free runtime(exit) */
+    mr_kthread_put(kth);
+    return 0;
 }
 
 mr_err_t mr_kthread_exit(mr_kthread_t *kth) {
@@ -313,16 +355,16 @@ MR_INLINE mr_kthread_t *kthread_self(void) {
     mr_kos_t *kos;
 
     /* Get kos */
-    kos = mr_kos_get();
+    kos = mr_kos_get(mr_kos_find());
     if (!kos) {
         return MR_NULL;
     }
 
     /* Get kthread self */
-    ret = MR_KOS_KTH_OPS(mr_kos_get())->self();
+    ret = MR_KOS_KTH_OPS(kos)->self();
 
     /* Put kos */
-    mr_kos_put();
+    mr_kos_put(kos);
     return ret;
 }
 
@@ -342,8 +384,8 @@ void mr_kthread_cleanup(mr_kthread_t *kth) {
         return;
     }
 
-    /* Cleanup kthread */
-    mr_kobject_put((mr_kobject_t *)kth);
+    /* Free runtime(cleanup) */
+    mr_kthread_put(kth);
 }
 
 void mr_kthread_entry(mr_kthread_t *kth) {
@@ -354,23 +396,22 @@ void mr_kthread_entry(mr_kthread_t *kth) {
 
     /* Call kthread entry */
     ((void (*)(mr_kthread_t *, void *))kth->entry)(kth, kth->args);
+
+    /* Free runtime(exit) */
+    mr_kthread_put(kth);
 }
 
 MR_INLINE mr_kthread_t *kthread_release_kobj(mr_kobject_t *kobj) {
     mr_kthread_t *kth;
-    const void *res;
 
     /* Get kthread */
     kth = MR_CONTAINER_OF(kobj, mr_kthread_t, parent);
 
-    /* If resource is inline or takeover, not need to free */
-    res = ((kth->res != kth->ires) && (kth->entry)) ? kth->res : MR_NULL;
-    if (res) {
-        mr_free((void *)res);
-    }
+    /* Free kthread resource */
+    kthread_res_free(kth);
 
     /* Put kos */
-    mr_kos_put();
+    mr_kos_put(kth->os);
     return kth;
 }