/*

 * 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.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

# include <signal.h>

 // ***************************************************************

 // Platform dependent initialization and cleanup

 // ***************************************************************

void OSThread::pd_initialize() {

  _thread_id                         = 0;

  sigemptyset(&_caller_sigmask);

  _current_callback                  = NULL;

  _current_callback_lock = VM_Version::supports_compare_and_exchange() ? NULL

                    : new Mutex(Mutex::suspend_resume, "Callback_lock", true);

  _saved_interrupt_thread_state      = _thread_new;

  _vm_created_thread                 = false;

}

void OSThread::pd_destroy() {

}

// Synchronous interrupt support

//

// _current_callback == NULL          no pending callback

//                   == 1             callback_in_progress

//                   == other value   pointer to the pending callback

//

// CAS on v8 is implemented by using a global atomic_memory_operation_lock,

// which is shared by other atomic functions. It is OK for normal uses, but

// dangerous if used after some thread is suspended or if used in signal

// handlers. Instead here we use a special per-thread lock to synchronize

// updating _current_callback if we are running on v8. Note in general trying

// to grab locks after a thread is suspended is not safe, but it is safe for

// updating _current_callback, because synchronous interrupt callbacks are

// currently only used in:

// 1. GetThreadPC_Callback - used by WatcherThread to profile VM thread

// There is no overlap between the callbacks, which means we won't try to

// grab a thread's sync lock after the thread has been suspended while holding

// the same lock.

// used after a thread is suspended

static intptr_t compare_and_exchange_current_callback (

       intptr_t callback, intptr_t *addr, intptr_t compare_value, Mutex *sync) {

  if (VM_Version::supports_compare_and_exchange()) {

    return Atomic::cmpxchg_ptr(callback, addr, compare_value);

  } else {

    MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);

    if (*addr == compare_value) {

      *addr = callback;

      return compare_value;

    } else {

      return callback;

    }

  }

}

// used in signal handler

static intptr_t exchange_current_callback(intptr_t callback, intptr_t *addr, Mutex *sync) {

  if (VM_Version::supports_compare_and_exchange()) {

    return Atomic::xchg_ptr(callback, addr);

  } else {

    MutexLockerEx ml(sync, Mutex::_no_safepoint_check_flag);

    intptr_t cb = *addr;

    *addr = callback;

    return cb;

  }

}

// one interrupt at a time. spin if _current_callback != NULL

int OSThread::set_interrupt_callback(Sync_Interrupt_Callback * cb) {

  int count = 0;

  while (compare_and_exchange_current_callback(

         (intptr_t)cb, (intptr_t *)&_current_callback, (intptr_t)NULL, _current_callback_lock) != NULL) {

    while (_current_callback != NULL) {

      count++;

#ifdef ASSERT

      if ((WarnOnStalledSpinLock > 0) &&

          (count % WarnOnStalledSpinLock == 0)) {

          warning("_current_callback seems to be stalled: %p", _current_callback);

      }

#endif

      os::yield_all(count);

    }

  }

  return 0;

}

// reset _current_callback, spin if _current_callback is callback_in_progress

void OSThread::remove_interrupt_callback(Sync_Interrupt_Callback * cb) {

  int count = 0;

  while (compare_and_exchange_current_callback(

         (intptr_t)NULL, (intptr_t *)&_current_callback, (intptr_t)cb, _current_callback_lock) != (intptr_t)cb) {

#ifdef ASSERT

    intptr_t p = (intptr_t)_current_callback;

    assert(p == (intptr_t)callback_in_progress ||

           p == (intptr_t)cb, "wrong _current_callback value");

#endif

    while (_current_callback != cb) {

      count++;

#ifdef ASSERT

      if ((WarnOnStalledSpinLock > 0) &&

          (count % WarnOnStalledSpinLock == 0)) {

          warning("_current_callback seems to be stalled: %p", _current_callback);

      }

#endif

      os::yield_all(count);

    }

  }

}

void OSThread::do_interrupt_callbacks_at_interrupt(InterruptArguments *args) {

  Sync_Interrupt_Callback * cb;

  cb = (Sync_Interrupt_Callback *)exchange_current_callback(

        (intptr_t)callback_in_progress, (intptr_t *)&_current_callback, _current_callback_lock);

  if (cb == NULL) {

    // signal is delivered too late (thread is masking interrupt signal??).

    // there is nothing we need to do because requesting thread has given up.

  } else if ((intptr_t)cb == (intptr_t)callback_in_progress) {

    fatal("invalid _current_callback state");

  } else {

    assert(cb->target()->osthread() == this, "wrong target");

    cb->execute(args);

    cb->leave_callback();             // notify the requester

  }

  // restore original _current_callback value

  intptr_t p;

  p = exchange_current_callback((intptr_t)cb, (intptr_t *)&_current_callback, _current_callback_lock);

  assert(p == (intptr_t)callback_in_progress, "just checking");

}

// Called by the requesting thread to send a signal to target thread and

// execute "this" callback from the signal handler.

int OSThread::Sync_Interrupt_Callback::interrupt(Thread * target, int timeout) {

  // Let signals to the vm_thread go even if the Threads_lock is not acquired

  assert(Threads_lock->owned_by_self() || (target == VMThread::vm_thread()),

         "must have threads lock to call this");

  OSThread * osthread = target->osthread();

  // may block if target thread already has a pending callback

  osthread->set_interrupt_callback(this);

  _target = target;

  int rslt = thr_kill(osthread->thread_id(), os::Solaris::SIGasync());

  assert(rslt == 0, "thr_kill != 0");

  bool status = false;

  jlong t1 = os::javaTimeMillis();

  { // don't use safepoint check because we might be the watcher thread.

    MutexLockerEx ml(_sync, Mutex::_no_safepoint_check_flag);

    while (!is_done()) {

      status = _sync->wait(Mutex::_no_safepoint_check_flag, timeout);

      // status == true if timed out

      if (status) break;

      // update timeout

      jlong t2 = os::javaTimeMillis();

      timeout -= t2 - t1;

      t1 = t2;

    }

  }

  // reset current_callback

  osthread->remove_interrupt_callback(this);

  return status;

}

void OSThread::Sync_Interrupt_Callback::leave_callback() {

  if (!_sync->owned_by_self()) {

    // notify requesting thread

    MutexLockerEx ml(_sync, Mutex::_no_safepoint_check_flag);

    _is_done = true;

    _sync->notify_all();

  } else {

    // Current thread is interrupted while it is holding the _sync lock, trying

    // to grab it again will deadlock. The requester will timeout anyway,

    // so just return.

    _is_done = true;

  }

}

// copied from synchronizer.cpp

void OSThread::handle_spinlock_contention(int tries) {

  if (NoYieldsInMicrolock) return;

  if (tries > 10) {

    os::yield_all(tries); // Yield to threads of any priority

  } else if (tries > 5) {

    os::yield();          // Yield to threads of same or higher priority

  }

}