1 /*
2 * Copyright (c) 1998, 2008, 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 // do not include precompiled header file
26 # include "incls/_osThread_solaris.cpp.incl"
27 # include <signal.h>
28
29 // ***************************************************************
30 // Platform dependent initialization and cleanup
31 // ***************************************************************
32
33 void OSThread::pd_initialize() {
34 _thread_id = 0;
35 sigemptyset(&_caller_sigmask);
36
37 _current_callback = NULL;
38 _current_callback_lock = VM_Version::supports_compare_and_exchange() ? NULL
39 : new Mutex(Mutex::suspend_resume, "Callback_lock", true);
40
41 _saved_interrupt_thread_state = _thread_new;
42 _vm_created_thread = false;
43 }
44
45 void OSThread::pd_destroy() {
46 }
47
48 // Synchronous interrupt support
49 //
50 // _current_callback == NULL no pending callback
51 // == 1 callback_in_progress
52 // == other value pointer to the pending callback
53 //
54
55 // CAS on v8 is implemented by using a global atomic_memory_operation_lock,
56 // which is shared by other atomic functions. It is OK for normal uses, but
57 // dangerous if used after some thread is suspended or if used in signal
58 // handlers. Instead here we use a special per-thread lock to synchronize
59 // updating _current_callback if we are running on v8. Note in general trying
60 // to grab locks after a thread is suspended is not safe, but it is safe for
61 // updating _current_callback, because synchronous interrupt callbacks are
62 // currently only used in:
63 // 1. GetThreadPC_Callback - used by WatcherThread to profile VM thread
64 // There is no overlap between the callbacks, which means we won't try to
65 // grab a thread's sync lock after the thread has been suspended while holding
66 // the same lock.
67
68 // used after a thread is suspended
69 static intptr_t compare_and_exchange_current_callback (
70 intptr_t callback, intptr_t *addr, intptr_t compare_value, Mutex *sync) {
71 if (VM_Version::supports_compare_and_exchange()) {
72 return Atomic::cmpxchg_ptr(callback, addr, compare_value);
73 } else {
74 MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);
75 if (*addr == compare_value) {
76 *addr = callback;
77 return compare_value;
78 } else {
79 return callback;
80 }
81 }
82 }
83
84 // used in signal handler
85 static intptr_t exchange_current_callback(intptr_t callback, intptr_t *addr, Mutex *sync) {
86 if (VM_Version::supports_compare_and_exchange()) {
87 return Atomic::xchg_ptr(callback, addr);
88 } else {
89 MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);
90 intptr_t cb = *addr;
91 *addr = callback;
92 return cb;
93 }
94 }
95
96 // one interrupt at a time. spin if _current_callback != NULL
97 int OSThread::set_interrupt_callback(Sync_Interrupt_Callback * cb) {
98 int count = 0;
99 while (compare_and_exchange_current_callback(
100 (intptr_t)cb, (intptr_t *)&_current_callback, (intptr_t)NULL, _current_callback_lock) != NULL) {
101 while (_current_callback != NULL) {
102 count++;
103 #ifdef ASSERT
104 if ((WarnOnStalledSpinLock > 0) &&
105 (count % WarnOnStalledSpinLock == 0)) {
106 warning("_current_callback seems to be stalled: %p", _current_callback);
107 }
108 #endif
109 os::yield_all(count);
110 }
111 }
112 return 0;
113 }
114
115 // reset _current_callback, spin if _current_callback is callback_in_progress
116 void OSThread::remove_interrupt_callback(Sync_Interrupt_Callback * cb) {
117 int count = 0;
118 while (compare_and_exchange_current_callback(
119 (intptr_t)NULL, (intptr_t *)&_current_callback, (intptr_t)cb, _current_callback_lock) != (intptr_t)cb) {
120 #ifdef ASSERT
121 intptr_t p = (intptr_t)_current_callback;
122 assert(p == (intptr_t)callback_in_progress ||
123 p == (intptr_t)cb, "wrong _current_callback value");
124 #endif
125 while (_current_callback != cb) {
126 count++;
127 #ifdef ASSERT
128 if ((WarnOnStalledSpinLock > 0) &&
129 (count % WarnOnStalledSpinLock == 0)) {
130 warning("_current_callback seems to be stalled: %p", _current_callback);
131 }
132 #endif
133 os::yield_all(count);
134 }
135 }
136 }
137
138 void OSThread::do_interrupt_callbacks_at_interrupt(InterruptArguments *args) {
139 Sync_Interrupt_Callback * cb;
140 cb = (Sync_Interrupt_Callback *)exchange_current_callback(
141 (intptr_t)callback_in_progress, (intptr_t *)&_current_callback, _current_callback_lock);
142
143 if (cb == NULL) {
144 // signal is delivered too late (thread is masking interrupt signal??).
145 // there is nothing we need to do because requesting thread has given up.
146 } else if ((intptr_t)cb == (intptr_t)callback_in_progress) {
147 fatal("invalid _current_callback state");
148 } else {
149 assert(cb->target()->osthread() == this, "wrong target");
150 cb->execute(args);
151 cb->leave_callback(); // notify the requester
152 }
153
154 // restore original _current_callback value
155 intptr_t p;
156 p = exchange_current_callback((intptr_t)cb, (intptr_t *)&_current_callback, _current_callback_lock);
157 assert(p == (intptr_t)callback_in_progress, "just checking");
158 }
159
160 // Called by the requesting thread to send a signal to target thread and
161 // execute "this" callback from the signal handler.
162 int OSThread::Sync_Interrupt_Callback::interrupt(Thread * target, int timeout) {
163 // Let signals to the vm_thread go even if the Threads_lock is not acquired
164 assert(Threads_lock->owned_by_self() || (target == VMThread::vm_thread()),
165 "must have threads lock to call this");
166
167 OSThread * osthread = target->osthread();
168
169 // may block if target thread already has a pending callback
170 osthread->set_interrupt_callback(this);
171
172 _target = target;
173
174 int rslt = thr_kill(osthread->thread_id(), os::Solaris::SIGasync());
175 assert(rslt == 0, "thr_kill != 0");
176
177 bool status = false;
178 jlong t1 = os::javaTimeMillis();
179 { // don't use safepoint check because we might be the watcher thread.
180 MutexLockerEx ml(_sync, Mutex::_no_safepoint_check_flag);
181 while (!is_done()) {
182 status = _sync->wait(Mutex::_no_safepoint_check_flag, timeout);
183
184 // status == true if timed out
185 if (status) break;
186
187 // update timeout
188 jlong t2 = os::javaTimeMillis();
189 timeout -= t2 - t1;
190 t1 = t2;
191 }
192 }
193
194 // reset current_callback
195 osthread->remove_interrupt_callback(this);
196
197 return status;
198 }
199
200 void OSThread::Sync_Interrupt_Callback::leave_callback() {
201 if (!_sync->owned_by_self()) {
202 // notify requesting thread
203 MutexLockerEx ml(_sync, Mutex::_no_safepoint_check_flag);
204 _is_done = true;
205 _sync->notify_all();
206 } else {
207 // Current thread is interrupted while it is holding the _sync lock, trying
208 // to grab it again will deadlock. The requester will timeout anyway,
209 // so just return.
210 _is_done = true;
211 }
212 }
213
214 // copied from synchronizer.cpp
215
216 void OSThread::handle_spinlock_contention(int tries) {
217 if (NoYieldsInMicrolock) return;
218
219 if (tries > 10) {
220 os::yield_all(tries); // Yield to threads of any priority
221 } else if (tries > 5) {
222 os::yield(); // Yield to threads of same or higher priority
223 }
224 }