I guess the question is, does the JMM guarantee that T2 sees w == true.
Since w is not protected by a monitor is it not reasonable to read w
in T2 before T1 releases M?
On 20/02/2004, at 6:26 PM, Bill Pugh wrote:
>
> On Feb 20, 2004, at 5:16 PM, Adam Welc wrote:
>>
>>
>> Is the following program correctly synchronized?
>>
>>
>> public static boolean w = false;
>> public static boolean v = false;
>>
>> T1 T2
>> w=true; while(true) {
>> synchronized(M) { synchronized(M) {
>> v =true; if (v) break;
>> } }
>> }
>> boolean tmp=w;
>
> Unless I'm missing something, this program is correctly synchronized.
>
> All accesses to v are guarded by the lock on M.
> If T1 and T2 both access w, you know that T1 must have released a lock
> on M that
> was then acquired by T2 before T2 reads w. So accesses to w are
> correctly synchronized.
>
> What makes you think this program may not be correctly synchronized?
>
> Bill
>
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