CODEWITHSUNDEEP
javajvmjava-native-interface
Leo
Leo

Reputation: 71

Why is sun.misc.Unsafe.unpark() described 'Unsafe'?

There is a comment above

public native void unpark(Object thread);

"Unblock the given thread blocked on park, or, if it is not blocked, cause the subsequent call to park not to block. Note: this operation is "unsafe" solely because the caller must somehow ensure that the thread has not been destroyed. Nothing special is usually required to ensure this when called from Java (in which there will ordinarily be a live reference to the thread) but this is not nearly-automatically so when calling from native code."

But why called by native code will bring in a destroyed thread?

Upvotes: 0

Views: 698

Answers (1)

apangin
apangin

Reputation: 98324

The comment is probably outdated. I do not see any calls to Unsafe.unpark from either JDK or HotSpot natives.

Moreover, LockSupport.unpark calls Unsafe.unpark directly. At the same time LockSupport is public API, so it must be safe.

Upvotes: 1

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