Do not cache RequiresConstructorBarrier() results.
Avoid caching the results. Caching was broken for JIT in the
presence of class unloading; entries for unloaded dex files
were leaked and potentially used erroneously with a newly
loaded dex file.
Test: m test-art-host-gtest
Test: testrunner.py --host
Test: Pixel 2 XL boots.
Test: m test-art-target-gtest
Test: testrunner.py --target
Bug: 118808764
Change-Id: Ic1163601170364e060c2e3009752f543c9bb37b7
diff --git a/compiler/driver/dex_compilation_unit.h b/compiler/driver/dex_compilation_unit.h
index 9d9c218..757f0e7 100644
--- a/compiler/driver/dex_compilation_unit.h
+++ b/compiler/driver/dex_compilation_unit.h
@@ -123,6 +123,41 @@
return compiling_class_;
}
+ // Does this <init> method require a constructor barrier (prior to the return)?
+ // The answer is "yes", if and only if the class has any instance final fields.
+ // (This must not be called for any non-<init> methods; the answer would be "no").
+ //
+ // ---
+ //
+ // JLS 17.5.1 "Semantics of final fields" mandates that all final fields are frozen at the end
+ // of the invoked constructor. The constructor barrier is a conservative implementation means of
+ // enforcing the freezes happen-before the object being constructed is observable by another
+ // thread.
+ //
+ // Note: This question only makes sense for instance constructors;
+ // static constructors (despite possibly having finals) never need
+ // a barrier.
+ //
+ // JLS 12.4.2 "Detailed Initialization Procedure" approximately describes
+ // class initialization as:
+ //
+ // lock(class.lock)
+ // class.state = initializing
+ // unlock(class.lock)
+ //
+ // invoke <clinit>
+ //
+ // lock(class.lock)
+ // class.state = initialized
+ // unlock(class.lock) <-- acts as a release
+ //
+ // The last operation in the above example acts as an atomic release
+ // for any stores in <clinit>, which ends up being stricter
+ // than what a constructor barrier needs.
+ //
+ // See also QuasiAtomic::ThreadFenceForConstructor().
+ bool RequiresConstructorBarrier() const;
+
private:
const Handle<mirror::ClassLoader> class_loader_;