--- a/src/proc.c	Thu Jan 17 19:55:30 2019 +0900
+++ b/src/proc.c	Fri Jan 18 09:40:22 2019 +0900
@@ -353,6 +353,34 @@
     }
 }
 
+__code cbc_sched(__code(*next)())
+{
+    int intena;
+
+    if(!holding(&ptable.lock)) {
+        panic("sched ptable.lock");
+    }
+
+    if(cpu->ncli != 1) {
+        panic("sched locks");
+    }
+
+    if(proc->state == RUNNING) {
+        panic("sched running");
+    }
+
+    if(int_enabled ()) {
+        panic("sched interruptible");
+    }
+
+    intena = cpu->intena;
+    swtch(&proc->context, cpu->scheduler);
+    cpu->intena = intena;
+
+    goto next();
+}
+
+
 // Enter scheduler.  Must hold only ptable.lock
 // and have changed proc->state.
 void sched(void)