From: Brian Norris <banorris@uci.edu>
Date: Wed, 27 Mar 2013 20:03:43 +0000 (-0700)
Subject: threads: move circular wait check into Threads::is_waiting_on
X-Git-Tag: oopsla2013~120
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=a11b6cce3a692a041cbfb772282a68be7949eb02;p=model-checker.git

threads: move circular wait check into Threads::is_waiting_on

A Threads::is_waiting_on(Thread *) interface  provides a more generic
interface, which can be useful for tasks other than just circular wait
deadlock detection.
---

diff --git a/model.cc b/model.cc
index 7df70ee..879f1de 100644
--- a/model.cc
+++ b/model.cc
@@ -409,22 +409,6 @@ bool ModelChecker::is_deadlocked() const
 	return blocking_threads;
 }
 
-/**
- * Check if a Thread has entered a circular wait deadlock situation. This will
- * not check other threads for potential deadlock situations, and may miss
- * deadlocks involving WAIT.
- *
- * @param t The thread which may have entered a deadlock
- * @return True if this Thread entered a deadlock; false otherwise
- */
-bool ModelChecker::is_circular_wait(const Thread *t) const
-{
-	for (Thread *waiting = t->waiting_on() ; waiting != NULL; waiting = waiting->waiting_on())
-		if (waiting == t)
-			return true;
-	return false;
-}
-
 /**
  * Check if this is a complete execution. That is, have all thread completed
  * execution (rather than exiting because sleep sets have forced a redundant
@@ -3169,7 +3153,7 @@ void ModelChecker::run()
 				Thread *thr = get_thread(tid);
 				if (!thr->is_model_thread() && !thr->is_complete() && !thr->get_pending()) {
 					switch_from_master(thr);
-					if (is_circular_wait(thr))
+					if (thr->is_waiting_on(thr))
 						assert_bug("Deadlock detected");
 				}
 			}
diff --git a/model.h b/model.h
index 355764b..6809612 100644
--- a/model.h
+++ b/model.h
@@ -282,7 +282,6 @@ private:
 	bool is_feasible_prefix_ignore_relseq() const;
 	bool is_infeasible() const;
 	bool is_deadlocked() const;
-	bool is_circular_wait(const Thread *t) const;
 	bool is_complete_execution() const;
 	bool have_bug_reports() const;
 	void print_bugs() const;
diff --git a/threads-model.h b/threads-model.h
index eb0fd43..eed11cb 100644
--- a/threads-model.h
+++ b/threads-model.h
@@ -105,6 +105,7 @@ public:
 	void set_pending(ModelAction *act) { pending = act; }
 
 	Thread * waiting_on() const;
+	bool is_waiting_on(const Thread *t) const;
 
 	/**
 	 * Remove one ModelAction from the waiting list
diff --git a/threads.cc b/threads.cc
index 00e5c2f..e4b4656 100644
--- a/threads.cc
+++ b/threads.cc
@@ -199,7 +199,7 @@ void Thread::set_state(thread_state s)
 }
 
 /**
- * Get the Thread that this Thread is waiting on
+ * Get the Thread that this Thread is immediately waiting on
  * @return The thread we are waiting on, if any; otherwise NULL
  */
 Thread * Thread::waiting_on() const
@@ -213,3 +213,19 @@ Thread * Thread::waiting_on() const
 		return (Thread *)pending->get_mutex()->get_state()->locked;
 	return NULL;
 }
+
+/**
+ * Check if this Thread is waiting (blocking) on a given Thread, directly or
+ * indirectly (via a chain of waiting threads)
+ *
+ * @param t The Thread on which we may be waiting
+ * @return True if we are waiting on Thread t; false otherwise
+ */
+bool Thread::is_waiting_on(const Thread *t) const
+{
+	Thread *wait;
+	for (wait = waiting_on(); wait != NULL; wait = wait->waiting_on())
+		if (wait == t)
+			return true;
+	return false;
+}