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 }