CODEWITHSUNDEEP
javaconcurrencyannotations
alexeykuzmin0
alexeykuzmin0

Reputation: 6440

How to use several mutexes in @GuardedBy annotation?

I have a method which should thread-safely do some processing over multiple fields of the class. This method is called in multiple loops, thus I don't lock any mutexes inside it, but require a caller to lock them, using a @GuardedBy annotation, something like this:

@GuardedBy("this")
void foo(int x) {
    mField1 = x + mField2;
    mField2 = x;
}

But to make my class faster I introduce a fine-grained locking. mField1 and mField2 sometimes are updated simultaneously, but sometimes are not, thus I introduce separate locks for them. How do I represent this logic in the annotation?

I tried coding something like

@GuardedBy("mField1Lock")
@GuardedBy("mField2Lock")
void foo(int x) {
    mField1 = x + mField2;
    mField2 = x;
}

But it does not compile: error: GuardedBy is not a repeatable annotation type.

Upvotes: 0

Views: 615

Answers (1)

mernst
mernst

Reputation: 8137

The @GuardedBy annotation defined by JCIP (Java Concurrency In Practice) does not permit multiple mutexes. Another problem is that JCIP provides no tool to check the annotations, but only uses them as documentation.

The Checker Framework solves both of these problems. Its @GuardedBy annotation permits multiple mutexes, and its Lock Checker verifies the annotations, warning you about anywhere that your code might suffer a race condition due to failure to acquire a lock.

Upvotes: 1

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