fix possibility deadlock in send method

ryblovAV · ryblovAV · commit 94cf9bb71689 · 2015-08-19T05:53:34.000+03:00
diff --git a/src/main/scala/org/learningconcurrency/exercises/ch2/ex7.scala b/src/main/scala/org/learningconcurrency/exercises/ch2/ex7.scala
@@ -18,12 +18,19 @@ object Ex7 extends App {
       a2.money += n
     }
 
-    a1.synchronized {
+    if (a1.uid < a2.uid) {
+      a1.synchronized {
+        a2.synchronized {
+          adjust()
+        }
+      }
+    } else {
       a2.synchronized {
-        adjust()
+        a1.synchronized {
+          adjust()
+        }
       }
     }
-
   }
 
   def sendAll(accounts: Set[Account], target: Account):Unit = {

Original file line number	Diff line number	Diff line change
`@@ -18,12 +18,19 @@ object Ex7 extends App {`
`18`	`18`	`a2.money += n`
`19`	`19`	`}`
`20`	`20`
`21`		`- a1.synchronized {`
	`21`	`+ if (a1.uid < a2.uid) {`
	`22`	`+ a1.synchronized {`
	`23`	`+ a2.synchronized {`
	`24`	`+ adjust()`
	`25`	`+ }`
	`26`	`+ }`
	`27`	`+ } else {`
`22`	`28`	`a2.synchronized {`
`23`		`- adjust()`
	`29`	`+ a1.synchronized {`
	`30`	`+ adjust()`
	`31`	`+ }`
`24`	`32`	`}`
`25`	`33`	`}`
`26`		`-`
`27`	`34`	`}`
`28`	`35`
`29`	`36`	`def sendAll(accounts: Set[Account], target: Account):Unit = {`