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8222518: Remove unnecessary caching of Parker object in java.lang.Thread

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Reviewed-by: dcubed, rehn
This commit is contained in:
David Holmes 2019-04-26 00:57:03 -04:00
parent f50047aa8e
commit ded4f6b5cf
4 changed files with 7 additions and 41 deletions
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23
src/hotspot/share/prims/unsafe.cpp
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@ -949,27 +949,16 @@ UNSAFE_ENTRY(void, Unsafe_Unpark(JNIEnv *env, jobject unsafe, jobject jthread))
(void) tlh.cv_internal_thread_to_JavaThread(jthread, &thr, &java_thread);
if (java_thread != NULL) {
// This is a valid oop.
jlong lp = java_lang_Thread::park_event(java_thread);
if (lp != 0) {
// This cast is OK even though the jlong might have been read
// non-atomically on 32bit systems, since there, one word will
// always be zero anyway and the value set is always the same
p = (Parker*)addr_from_java(lp);
} else {
// Not cached in the java.lang.Thread oop yet (could be an
// older version of library).
if (thr != NULL) {
// The JavaThread is alive.
p = thr->parker();
if (p != NULL) {
// Cache the Parker in the java.lang.Thread oop for next time.
java_lang_Thread::set_park_event(java_thread, addr_to_java(p));
}
}
if (thr != NULL) {
// The JavaThread is alive.
p = thr->parker();
}
}
} // ThreadsListHandle is destroyed here.
// 'p' points to type-stable-memory if non-NULL. If the target
// thread terminates before we get here the new user of this
// Parker will get a 'spurious' unpark - which is perfectly valid.
if (p != NULL) {
HOTSPOT_THREAD_UNPARK((uintptr_t) p);
p->unpark();