diff -ruN kozos38/kozos.h kozos39/kozos.h
--- kozos38/kozos.h	Mon Jan 26 22:57:44 2009
+++ kozos39/kozos.h	Sun Feb  1 19:44:01 2009
@@ -27,6 +27,12 @@
 void *kz_memalloc(int size);
 int kz_memfree(void *p);
 
+/* srvcall */
+int kx_wakeup(int id);
+int kx_send(int id, int size, char *p);
+void *kx_kmalloc(int size);
+int kx_kmfree(void *p);
+
 /* library */
 void kz_start(kz_func func, char *name, int pri, int argc, char *argv[]);
 void kz_sysdown();
diff -ruN kozos38/syscall.c kozos39/syscall.c
--- kozos38/syscall.c	Mon Jan 26 22:57:44 2009
+++ kozos39/syscall.c	Sun Feb  1 19:44:01 2009
@@ -15,6 +15,8 @@
   return;
 }
 
+/* System Call */
+
 int kz_run(kz_func func, char *name, int pri, int argc, char *argv[])
 {
   kz_syscall_param_t param;
@@ -160,4 +162,40 @@
   param.un.memfree.p = p;
   kz_syscall(KZ_SYSCALL_TYPE_MEMFREE, &param);
   return param.un.memfree.ret;
+}
+
+/* Service Call */
+
+int kx_wakeup(int id)
+{
+  kz_syscall_param_t param;
+  param.un.wakeup.id = id;
+  kz_srvcall(KZ_SYSCALL_TYPE_WAKEUP, &param);
+  return param.un.wakeup.ret;
+}
+
+int kx_send(int id, int size, char *p)
+{
+  kz_syscall_param_t param;
+  param.un.send.id = id;
+  param.un.send.size = size;
+  param.un.send.p = p;
+  kz_srvcall(KZ_SYSCALL_TYPE_SEND, &param);
+  return param.un.send.ret;
+}
+
+void *kx_kmalloc(int size)
+{
+  kz_syscall_param_t param;
+  param.un.kmalloc.size = size;
+  kz_srvcall(KZ_SYSCALL_TYPE_KMALLOC, &param);
+  return param.un.kmalloc.ret;
+}
+
+int kx_kmfree(void *p)
+{
+  kz_syscall_param_t param;
+  param.un.kmfree.p = p;
+  kz_srvcall(KZ_SYSCALL_TYPE_KMFREE, &param);
+  return param.un.kmfree.ret;
 }
diff -ruN kozos38/syscall.h kozos39/syscall.h
--- kozos38/syscall.h	Mon Jan 26 22:57:44 2009
+++ kozos39/syscall.h	Sun Feb  1 19:44:01 2009
@@ -106,5 +106,6 @@
 } kz_syscall_param_t;
 
 void kz_syscall(kz_syscall_type_t type, kz_syscall_param_t *param);
+void kz_srvcall(kz_syscall_type_t type, kz_syscall_param_t *param);
 
 #endif
diff -ruN kozos38/thread.c kozos39/thread.c
--- kozos38/thread.c	Mon Jan 26 22:57:44 2009
+++ kozos39/thread.c	Sun Feb  1 19:44:01 2009
@@ -23,7 +23,6 @@
 static kz_handler handlers[SIG_NUM];
 static int debug_sockt = 0;
 sigset_t block;
-static sigset_t block_sys;
 static sigset_t block_old;
 static int block_count = 0;
 static stack_t intrstack;
@@ -265,25 +264,8 @@
 
 static void extintr_proc(int signo)
 {
-  /*
-   * システムコールのパラメータ格納にコンテキストが必要なので，
-   * 割り込み処理用のコンテキストを確保する．
-   * (割り込みがネストしたときのために，スタック上に確保する)
-   */
-  kz_thread intrcontext;
-  kz_thread *current_save;
-
-  if (handlers[signo]) {
-    memset(&intrcontext, 0, sizeof(intrcontext));
-    current_save = current;
-    current = &intrcontext;
-
-    sigprocmask(SIG_UNBLOCK, &block_sys, NULL);
+  if (handlers[signo])
     handlers[signo](signo);
-    sigprocmask(SIG_BLOCK, &block_sys, NULL);
-
-    current = current_save;
-  }
   if (sigcalls[signo])
     sendmsg(sigcalls[signo], 0, 0, NULL);
 }
@@ -333,10 +315,8 @@
   return 0;
 }
 
-static void syscall_proc(kz_syscall_type_t type, kz_syscall_param_t *p)
+static void syscall_procedure(kz_syscall_type_t type, kz_syscall_param_t *p)
 {
-  getcurrent();
-
   /* システムコールの実行中にcurrentが書き換わるので注意 */
   switch (type) {
   case KZ_SYSCALL_TYPE_RUN:
@@ -402,6 +382,17 @@
   return;
 }
 
+static void syscall_proc(kz_syscall_type_t type, kz_syscall_param_t *p)
+{
+  getcurrent();
+  syscall_procedure(type, p);
+}
+
+static void srvcall_proc(kz_syscall_type_t type, kz_syscall_param_t *p)
+{
+  syscall_procedure(type, p);
+}
+
 static void schedule()
 {
 #if PRI_NUM > 32
@@ -436,6 +427,8 @@
 
 static void thread_intrvec(int signo, kz_thread *thp)
 {
+  kz_thread *current_old;
+
   switch (signo) {
   case SIGSYS: /* システムコール */
     syscall_proc(thp->syscall.type, thp->syscall.param);
@@ -469,12 +462,28 @@
     return;
   }
 
-  schedule();
+  current_old = NULL;
+  while (1) {
+    schedule();
+
+    if (current_old && (current == current_old))
+      break;
+
+    current_old = current;
+
+    if (current->precall) {
+      current->precall((int)current);
+    } else if (default_precall) {
+      default_precall((int)current);
+    } else {
+      break;
+    }
 
-  if (current->precall) {
-    current->precall((int)current);
-  } else if (default_precall) {
-    default_precall((int)current);
+    /*
+     * 上記 precall の呼び出し内部でサービスコールが呼ばれて current が
+     * 書きかわっていたり，もっと優先度の高いスレッドがレディー状態に
+     * なっている可能性があるので，スケジューリングしなおす．
+     */
   }
 
   /*
@@ -559,9 +568,6 @@
   sigaddset(&block, SIGTRAP);
   sigaddset(&block, SIGILL);
 
-  sigemptyset(&block_sys);
-  sigaddset(&block_sys, SIGSYS);
-
   thread_start(func, name, pri, argc, argv);
 
   /* ここには返ってこない */
@@ -600,4 +606,10 @@
       sigprocmask(SIG_SETMASK, &block_old, NULL);
     }
   }
+}
+
+void kz_srvcall(kz_syscall_type_t type, kz_syscall_param_t *param)
+{
+  srvcall_proc(type, param);
+  return;
 }