From a3e788d52494b75b927538c9c2bfee1573aa50e1 Mon Sep 17 00:00:00 2001
From: Matt Joiner <anacrolix@gmail.com>
Date: Wed, 30 Sep 2020 19:13:27 +1000
Subject: Wake watchers until the var changes again

---
 tx.go | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

(limited to 'tx.go')

diff --git a/tx.go b/tx.go
index f3bc617..f613efb 100644
--- a/tx.go
+++ b/tx.go
@@ -9,23 +9,25 @@ import (
 
 // A Tx represents an atomic transaction.
 type Tx struct {
-	reads    map[*Var]VarValue
-	writes   map[*Var]interface{}
-	watching map[*Var]struct{}
-	locks    txLocks
-	mu       sync.Mutex
-	cond     sync.Cond
-	tries    int
+	reads     map[*Var]VarValue
+	writes    map[*Var]interface{}
+	watching  map[*Var]struct{}
+	locks     txLocks
+	mu        sync.Mutex
+	cond      sync.Cond
+	waiting   bool
+	completed bool
+	tries     int
 }
 
 // Check that none of the logged values have changed since the transaction began.
-func (tx *Tx) verify() bool {
+func (tx *Tx) inputsChanged() bool {
 	for v, read := range tx.reads {
 		if read.Changed(v.value.Load().(VarValue)) {
-			return false
+			return true
 		}
 	}
-	return true
+	return false
 }
 
 // Writes the values in the transaction log to their respective Vars.
@@ -58,12 +60,15 @@ func (tx *Tx) wait() {
 	tx.updateWatchers()
 	tx.mu.Lock()
 	firstWait := true
-	for tx.verify() {
+	for !tx.inputsChanged() {
 		if !firstWait {
 			expvars.Add("wakes for unchanged versions", 1)
 		}
 		expvars.Add("waits", 1)
+		tx.waiting = true
+		tx.cond.Broadcast()
 		tx.cond.Wait()
+		tx.waiting = false
 		firstWait = false
 	}
 	tx.mu.Unlock()
-- 
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