Improve comment on thread_unblock().

Suggested by Godmar Back.

diff --git a/src/threads/thread.c b/src/threads/thread.c
index f6768c0225432617c92c40e517a00f75f6fd72b9..92d1aa899efe1d8bf84c6c7056ae7d45215c687b 100644 (file)
--- a/src/threads/thread.c
+++ b/src/threads/thread.c
@@ -216,7 +216,12 @@ thread_block (void)
 
 /* Transitions a blocked thread T to the ready-to-run state.
    This is an error if T is not blocked.  (Use thread_yield() to
-   make the running thread ready.) */
+   make the running thread ready.)
+
+   This function does not preempt the running thread.  This can
+   be important: if the caller had disabled interrupts itself,
+   it may expect that it can atomically unblock a thread and
+   update other data. */
 void
 thread_unblock (struct thread *t) 
 {