1 /* 2 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "memory/allocation.inline.hpp" 27 #include "runtime/thread.inline.hpp" 28 #include "runtime/threadSMR.hpp" 29 #include "services/threadService.hpp" 30 31 // 'entries + 1' so we always have at least one entry. 32 ThreadsList::ThreadsList(int entries) : _length(entries), _threads(NEW_C_HEAP_ARRAY(JavaThread*, entries + 1, mtThread)), _next_list(NULL) { 33 *(JavaThread**)(_threads + entries) = NULL; // Make sure the extra entry is NULL. 34 } 35 36 ThreadsList::~ThreadsList() { 37 FREE_C_HEAP_ARRAY(JavaThread*, _threads); 38 } 39 40 ThreadsListSetter::~ThreadsListSetter() { 41 if (_target_needs_release) { 42 // The hazard ptr in the target needs to be released. 43 Threads::release_stable_list(_target); 44 } 45 } 46 47 void ThreadsListSetter::set() { 48 assert(_target->get_threads_hazard_ptr() == NULL, "hazard ptr should not already be set"); 49 (void) Threads::acquire_stable_list(_target, /* is_ThreadsListSetter */ true); 50 _target_needs_release = true; 51 } 52 53 ThreadsListHandle::ThreadsListHandle(Thread *self) : _list(Threads::acquire_stable_list(self, /* is_ThreadsListSetter */ false)), _self(self) { 54 assert(self == Thread::current(), "sanity check"); 55 if (EnableThreadSMRStatistics) { 56 _timer.start(); 57 } 58 } 59 60 ThreadsListHandle::~ThreadsListHandle() { 61 Threads::release_stable_list(_self); 62 if (EnableThreadSMRStatistics) { 63 _timer.stop(); 64 uint millis = (uint)_timer.milliseconds(); 65 Threads::inc_smr_tlh_cnt(); 66 Threads::add_smr_tlh_times(millis); 67 Threads::update_smr_tlh_time_max(millis); 68 } 69 } 70 71 // Convert an internal thread reference to a JavaThread found on the 72 // associated ThreadsList. This ThreadsListHandle "protects" the 73 // returned JavaThread *. 74 // 75 // If thread_oop_p is not NULL, then the caller wants to use the oop 76 // after this call so the oop is returned. On success, *jt_pp is set 77 // to the converted JavaThread * and true is returned. On error, 78 // returns false. 79 // 80 bool ThreadsListHandle::cv_internal_thread_to_JavaThread(jobject jthread, 81 JavaThread ** jt_pp, 82 oop * thread_oop_p) { 83 assert(this->list() != NULL, "must have a ThreadsList"); 84 assert(jt_pp != NULL, "must have a return JavaThread pointer"); 85 // thread_oop_p is optional so no assert() 86 87 // The JVM_* interfaces don't allow a NULL thread parameter; JVM/TI 88 // allows a NULL thread parameter to signify "current thread" which 89 // allows us to avoid calling cv_external_thread_to_JavaThread(). 90 // The JVM_* interfaces have no such leeway. 91 92 oop thread_oop = JNIHandles::resolve_non_null(jthread); 93 // Looks like an oop at this point. 94 if (thread_oop_p != NULL) { 95 // Return the oop to the caller; the caller may still want 96 // the oop even if this function returns false. 97 *thread_oop_p = thread_oop; 98 } 99 100 JavaThread *java_thread = java_lang_Thread::thread(thread_oop); 101 if (java_thread == NULL) { 102 // The java.lang.Thread does not contain a JavaThread * so it has 103 // not yet run or it has died. 104 return false; 105 } 106 // Looks like a live JavaThread at this point. 107 108 if (java_thread != JavaThread::current()) { 109 // jthread is not for the current JavaThread so have to verify 110 // the JavaThread * against the ThreadsList. 111 if (EnableThreadSMRExtraValidityChecks && !includes(java_thread)) { 112 // Not on the JavaThreads list so it is not alive. 113 return false; 114 } 115 } 116 117 // Return a live JavaThread that is "protected" by the 118 // ThreadsListHandle in the caller. 119 *jt_pp = java_thread; 120 return true; 121 }