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src/share/vm/runtime/jniHandles.hpp
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rev 12692 : 8176100: [REDO][REDO] G1 Needs pre barrier on dereference of weak JNI handles
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*** 1,7 ****
/*
! * Copyright (c) 1998, 2014, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
--- 1,7 ----
/*
! * Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*** 38,48 ****
--- 38,69 ----
private:
static JNIHandleBlock* _global_handles; // First global handle block
static JNIHandleBlock* _weak_global_handles; // First weak global handle block
static oop _deleted_handle; // Sentinel marking deleted handles
+ inline static bool is_jweak(jobject handle);
+ inline static oop& jobject_ref(jobject handle); // NOT jweak!
+ inline static oop& jweak_ref(jobject handle);
+
+ template<bool external_guard> inline static oop guard_value(oop value);
+ template<bool external_guard> inline static oop resolve_impl(jobject handle);
+ template<bool external_guard> static oop resolve_jweak(jweak handle);
+
public:
+ // Low tag bit in jobject used to distinguish a jweak. jweak is
+ // type equivalent to jobject, but there are places where we need to
+ // be able to distinguish jweak values from other jobjects, and
+ // is_weak_global_handle is unsuitable for performance reasons. To
+ // provide such a test we add weak_tag_value to the (aligned) byte
+ // address designated by the jobject to produce the corresponding
+ // jweak. Accessing the value of a jobject must account for it
+ // being a possibly offset jweak.
+ static const uintptr_t weak_tag_size = 1;
+ static const uintptr_t weak_tag_alignment = (1u << weak_tag_size);
+ static const uintptr_t weak_tag_mask = weak_tag_alignment - 1;
+ static const int weak_tag_value = 1;
+
// Resolve handle into oop
inline static oop resolve(jobject handle);
// Resolve externally provided handle into oop with some guards
inline static oop resolve_external_guard(jobject handle);
// Resolve handle into oop, result guaranteed not to be null
*** 174,212 ****
static bool any_contains(jobject handle); // Does any block currently in use contain handle
static void print_statistics();
#endif
};
! inline oop JNIHandles::resolve(jobject handle) {
! oop result = (handle == NULL ? (oop)NULL : *(oop*)handle);
! assert(result != NULL || (handle == NULL || !CheckJNICalls || is_weak_global_handle(handle)), "Invalid value read from jni handle");
! assert(result != badJNIHandle, "Pointing to zapped jni handle area");
return result;
! };
inline oop JNIHandles::resolve_external_guard(jobject handle) {
! if (handle == NULL) return NULL;
! oop result = *(oop*)handle;
! if (result == NULL || result == badJNIHandle) return NULL;
return result;
! };
!
inline oop JNIHandles::resolve_non_null(jobject handle) {
assert(handle != NULL, "JNI handle should not be null");
! oop result = *(oop*)handle;
! assert(result != NULL, "Invalid value read from jni handle");
! assert(result != badJNIHandle, "Pointing to zapped jni handle area");
! // Don't let that private _deleted_handle object escape into the wild.
! assert(result != deleted_handle(), "Used a deleted global handle.");
return result;
! };
inline void JNIHandles::destroy_local(jobject handle) {
if (handle != NULL) {
! *((oop*)handle) = deleted_handle(); // Mark the handle as deleted, allocate will reuse it
}
}
#endif // SHARE_VM_RUNTIME_JNIHANDLES_HPP
--- 195,282 ----
static bool any_contains(jobject handle); // Does any block currently in use contain handle
static void print_statistics();
#endif
};
+ inline bool JNIHandles::is_jweak(jobject handle) {
+ STATIC_ASSERT(weak_tag_size == 1);
+ STATIC_ASSERT(weak_tag_value == 1);
+ return (reinterpret_cast<uintptr_t>(handle) & weak_tag_mask) != 0;
+ }
! inline oop& JNIHandles::jobject_ref(jobject handle) {
! assert(!is_jweak(handle), "precondition");
! return *reinterpret_cast<oop*>(handle);
! }
!
! inline oop& JNIHandles::jweak_ref(jobject handle) {
! assert(is_jweak(handle), "precondition");
! char* ptr = reinterpret_cast<char*>(handle) - weak_tag_value;
! return *reinterpret_cast<oop*>(ptr);
! }
!
! // external_guard is true if called from resolve_external_guard.
! // Treat deleted (and possibly zapped) as NULL for external_guard,
! // else as (asserted) error.
! template<bool external_guard>
! inline oop JNIHandles::guard_value(oop value) {
! if (!external_guard) {
! assert(value != badJNIHandle, "Pointing to zapped jni handle area");
! assert(value != deleted_handle(), "Used a deleted global handle");
! } else if ((value == badJNIHandle) || (value == deleted_handle())) {
! value = NULL;
! }
! return value;
! }
!
! // external_guard is true if called from resolve_external_guard.
! template<bool external_guard>
! inline oop JNIHandles::resolve_impl(jobject handle) {
! assert(handle != NULL, "precondition");
! oop result;
! if (is_jweak(handle)) { // Unlikely
! result = resolve_jweak<external_guard>(handle);
! } else {
! result = jobject_ref(handle);
! // Construction of jobjects canonicalize a null value into a null
! // jobject, so for non-jweak the pointee should never be null.
! assert(external_guard || result != NULL,
! "Invalid value read from jni handle");
! result = guard_value<external_guard>(result);
! }
return result;
! }
+ inline oop JNIHandles::resolve(jobject handle) {
+ oop result = NULL;
+ if (handle != NULL) {
+ result = resolve_impl<false /* external_guard */ >(handle);
+ }
+ return result;
+ }
+ // Resolve some erroneous cases to NULL, rather than treating them as
+ // possibly unchecked errors. In particular, deleted handles are
+ // treated as NULL (though a deleted and later reallocated handle
+ // isn't detected).
inline oop JNIHandles::resolve_external_guard(jobject handle) {
! oop result = NULL;
! if (handle != NULL) {
! result = resolve_impl<true /* external_guard */ >(handle);
! }
return result;
! }
inline oop JNIHandles::resolve_non_null(jobject handle) {
assert(handle != NULL, "JNI handle should not be null");
! oop result = resolve_impl<false /* external_guard */ >(handle);
! assert(result != NULL, "NULL read from jni handle");
return result;
! }
inline void JNIHandles::destroy_local(jobject handle) {
if (handle != NULL) {
! jobject_ref(handle) = deleted_handle();
}
}
#endif // SHARE_VM_RUNTIME_JNIHANDLES_HPP
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