From ed73252cff03383a802a9608a97e5234bc90fcc4 Mon Sep 17 00:00:00 2001
From: Brian Norris <banorris@uci.edu>
Date: Tue, 2 Apr 2013 18:11:49 -0700
Subject: [PATCH] threads: remove wait_list

We can glean the "thread waiting" information without recording it
directly in a list for each thread.
---
 model.cc        | 10 ++++++----
 threads-model.h | 34 ----------------------------------
 threads.cc      |  2 --
 3 files changed, 6 insertions(+), 40 deletions(-)

diff --git a/model.cc b/model.cc
index 4d623611..557d103b 100644
--- a/model.cc
+++ b/model.cc
@@ -1219,9 +1219,12 @@ bool ModelChecker::process_thread_action(ModelAction *curr)
 	}
 	case THREAD_FINISH: {
 		Thread *th = get_thread(curr);
-		while (!th->wait_list_empty()) {
-			ModelAction *act = th->pop_wait_list();
-			scheduler->wake(get_thread(act));
+		/* Wake up any joining threads */
+		for (unsigned int i = 0; i < get_num_threads(); i++) {
+			Thread *waiting = get_thread(int_to_id(i));
+			if (waiting->waiting_on() == th &&
+					waiting->get_pending()->is_thread_join())
+				scheduler->wake(waiting);
 		}
 		th->complete();
 		/* Completed thread can't satisfy promises */
@@ -1464,7 +1467,6 @@ bool ModelChecker::check_action_enabled(ModelAction *curr) {
 	} else if (curr->is_thread_join()) {
 		Thread *blocking = curr->get_thread_operand();
 		if (!blocking->is_complete()) {
-			blocking->push_wait_list(curr);
 			thread_blocking_check_promises(blocking, get_thread(curr));
 			return false;
 		}
diff --git a/threads-model.h b/threads-model.h
index eed11cbb..ef2c9e10 100644
--- a/threads-model.h
+++ b/threads-model.h
@@ -78,23 +78,6 @@ public:
 	/** @return True if this thread is blocked */
 	bool is_blocked() const { return state == THREAD_BLOCKED; }
 
-	/** @return True if no threads are waiting on this Thread */
-	bool wait_list_empty() const { return wait_list.empty(); }
-
-	/**
-	 * Add a ModelAction to the waiting list for this thread.
-	 * @param t The ModelAction to add. Must be a JOIN.
-	 */
-	void push_wait_list(ModelAction *act) { wait_list.push_back(act); }
-
-	unsigned int num_wait_list() const {
-		return wait_list.size();
-	}
-
-	ModelAction * get_waiter(unsigned int i) const {
-		return wait_list[i];
-	}
-
 	/** @return The pending (next) ModelAction for this Thread
 	 *  @see Thread::pending */
 	ModelAction * get_pending() const { return pending; }
@@ -107,16 +90,6 @@ public:
 	Thread * waiting_on() const;
 	bool is_waiting_on(const Thread *t) const;
 
-	/**
-	 * Remove one ModelAction from the waiting list
-	 * @return The ModelAction that was removed from the waiting list
-	 */
-	ModelAction * pop_wait_list() {
-		ModelAction *ret = wait_list.front();
-		wait_list.pop_back();
-		return ret;
-	}
-
 	bool is_model_thread() const { return model_thread; }
 
 	friend void thread_startup();
@@ -165,13 +138,6 @@ private:
 	thread_id_t id;
 	thread_state state;
 
-	/**
-	 * A list of ModelActions waiting on this Thread. Particularly, this
-	 * list is used for thread joins, where another Thread waits for this
-	 * Thread to complete
-	 */
-	SnapVector<ModelAction *> wait_list;
-
 	/**
 	 * The value returned by the last action in this thread
 	 * @see Thread::set_return_value()
diff --git a/threads.cc b/threads.cc
index e4b46561..5bfd0287 100644
--- a/threads.cc
+++ b/threads.cc
@@ -139,7 +139,6 @@ Thread::Thread(thread_id_t tid) :
 	user_thread(NULL),
 	id(tid),
 	state(THREAD_READY), /* Thread is always ready? */
-	wait_list(),
 	last_action_val(0),
 	model_thread(true)
 {
@@ -160,7 +159,6 @@ Thread::Thread(thrd_t *t, void (*func)(void *), void *a, Thread *parent) :
 	arg(a),
 	user_thread(t),
 	state(THREAD_CREATED),
-	wait_list(),
 	last_action_val(VALUE_NONE),
 	model_thread(false)
 {
-- 
2.34.1