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lingering wait()/notify() and deadlock doubt

 
Alexander Danilou
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Hi, can somebody help me with this?
A call to wait()/notify() will NOT prevent a deadlock - true of false?

I think it should be false, because when calling wait() thread releases the lock, so deadlock can be prevented.
But according to K&B the answer is true..
 
Henry Wong
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I think it should be false, because when calling wait() thread releases the lock, so deadlock can be prevented.


Just because a method releases a lock -- doesn't mean that it is a mechanism that can be used to prevent deadlocks. Can you explain how the method can be used to prevent deadlocks?

Henry
 
Devaka Cooray
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As Henry wrote, it cannot be used as a mechanism "to prevent deadlocks". But it "may" prevent deadlocks on some situations. In my view, this question cannot be accurately answered without having more details on it. Found your other topic.

Devaka.
 
Henry Wong
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But it "may" prevent deadlocks on some situations.


In theory, this may be true. In practice, I have never seen this done. In fact, even worrying about deadlocks is not common with many programmers...

And for developers that do worry about deadlocks (ie. the good ones)... Deadlock prevention techniques generally implemented are (1) using a coarse lock, or (2) lock ordering -- building a release mechanism just seems too elaborate and may even enforce using a "framework".

Henry
 
Henry Wong
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Devaka Cooray wrote:Found your other topic.


Thanks Devaka. I locked the other topic (and posted a link back to here).

Henry
 
Alexander Danilou
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Thank you,

Devaka wrote:
In my view, this question cannot be accurately answered without having more details on it.

This was exactly my concern. At this point I just want to pass SCJP exam. I really hope that real exam will not contain such questions. But since this statement and answer "true" is on the K&B Mock exam, I was concerned.
 
Devaka Cooray
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Henry Wong wrote:In theory, this may be true. In practice, I have never seen this done.

Completely agree. I can't even imagine a dead-lock situation in practice, which should be prevented by using wait()/notify() methods.

Devaka.
 
Devaka Cooray
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Alexander Danilou wrote:This was exactly my concern. At this point I just want to pass SCJP exam. I really hope that real exam will not contain such questions. But since this statement and answer "true" is on the K&B Mock exam, I was concerned.

You may encounter with same type questions on the real exam, but with some additional details. On that case it is no doubt to choose "true" as the correct answer.

Devaka.
 
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