3 files changed, 27 insertions, 8 deletions
diff --git a/arch/x86/machine/trap.c b/arch/x86/machine/trap.c
index 18bff6bc..26656204 100644
--- a/arch/x86/machine/trap.c
+++ b/arch/x86/machine/trap.c
@@ -150,7 +150,7 @@ trap_main(struct trap_frame *frame)
 {
     assert(frame->vector < ARRAY_SIZE(trap_handlers));
     trap_handlers[frame->vector].fn(frame);
-    thread_reschedule();
+    thread_intr_schedule();
 }
 
 #ifdef __LP64__
diff --git a/kern/thread.c b/kern/thread.c
index dcf038c3..27cdb1b5 100644
--- a/kern/thread.c
+++ b/kern/thread.c
@@ -251,7 +251,7 @@ thread_schedule(void)
 }
 
 void
-thread_reschedule(void)
+thread_intr_schedule(void)
 {
     struct thread_runq *runq;
     struct thread *thread;
@@ -267,6 +267,22 @@ thread_reschedule(void)
 }
 
 void
+thread_preempt_schedule(void)
+{
+    struct thread_runq *runq;
+    struct thread *thread;
+
+    runq = thread_runq_local();
+    thread = runq->current;
+    assert(thread != NULL);
+
+    if ((thread->preempt == 0)) {
+        assert(!cpu_intr_enabled());
+        thread_schedule();
+    }
+}
+
+void
 thread_tick(void)
 {
     struct thread_runq *runq;
diff --git a/kern/thread.h b/kern/thread.h
index 0022591d..b68b5b38 100644
--- a/kern/thread.h
+++ b/kern/thread.h
@@ -97,11 +97,14 @@ void __noreturn thread_run(void);
 void thread_schedule(void);
 
 /*
- * Invoke the scheduler if the current thread is marked for reschedule.
- *
- * Called from interrupt context.
+ * Invoke the scheduler from interrupt context.
+ */
+void thread_intr_schedule(void);
+
+/*
+ * Invoke the scheduler from preemption control functions.
  */
-void thread_reschedule(void);
+void thread_preempt_schedule(void);
 
 /*
  * Report a periodic timer interrupt on the thread currently running on
@@ -156,8 +159,8 @@ thread_preempt_enable(void)
     assert(thread->preempt != 0);
     thread->preempt--;
 
-    if ((thread->preempt == 0) && (thread->flags & THREAD_RESCHEDULE))
-        thread_schedule();
+    if (thread->flags & THREAD_RESCHEDULE)
+        thread_preempt_schedule();
 }
 
 static inline void