/*

 * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.

 * 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 "precompiled.hpp"

#include "logging/log.hpp"

#include "runtime/interfaceSupport.inline.hpp"

#include "runtime/mutex.hpp"

#include "runtime/osThread.hpp"

#include "runtime/safepointMechanism.inline.hpp"

#include "runtime/thread.inline.hpp"

#include "utilities/events.hpp"

#include "utilities/macros.hpp"

#ifdef ASSERT

void Monitor::check_safepoint_state(Thread* thread, bool do_safepoint_check) {

  // If the JavaThread checks for safepoint, verify that the lock wasn't created with safepoint_check_never.

  SafepointCheckRequired not_allowed = do_safepoint_check ?  Monitor::_safepoint_check_never :

                                                             Monitor::_safepoint_check_always;

  assert(!thread->is_Java_thread() || _safepoint_check_required != not_allowed,

         "This lock should %s have a safepoint check for Java threads: %s",

         _safepoint_check_required ? "always" : "never", name());

}

#endif // ASSERT

void Monitor::lock(Thread * self) {

  check_safepoint_state(self, true);

#ifdef CHECK_UNHANDLED_OOPS

  // Clear unhandled oops in JavaThreads so we get a crash right away.

  if (self->is_Java_thread()) {

    self->clear_unhandled_oops();

  }

#endif // CHECK_UNHANDLED_OOPS

  DEBUG_ONLY(check_prelock_state(self, StrictSafepointChecks));

  assert(_owner != self, "invariant");

  Monitor* in_flight_monitor = NULL;

  DEBUG_ONLY(int retry_cnt = 0;)

  while (!_lock.try_lock()) {

    // The lock is contended

  #ifdef ASSERT

    check_block_state(self);

    if (retry_cnt++ > 3) {

      log_trace(vmmonitor)("JavaThread " INTPTR_FORMAT " on %d attempt trying to acquire vmmonitor %s", p2i(self), retry_cnt, _name);

    }

  #endif // ASSERT

    if (self->is_Java_thread()) {

      assert(rank() > Mutex::special, "Potential deadlock with special or lesser rank mutex");

      { ThreadBlockInVMWithDeadlockCheck tbivmdc((JavaThread *) self, &in_flight_monitor);

        in_flight_monitor = this;  // save for ~ThreadBlockInVMWithDeadlockCheck

        _lock.lock();

      }

      if (in_flight_monitor != NULL) {

        // Not unlocked by ~ThreadBlockInVMWithDeadlockCheck

        break;

      }

    } else {

      _lock.lock();

      break;

    }

  }

  assert_owner(NULL);

  set_owner(self);

}

void Monitor::lock() {

  this->lock(Thread::current());

}

// Lock without safepoint check - a degenerate variant of lock() for use by

// JavaThreads when it is known to be safe to not check for a safepoint when

// acquiring this lock. If the thread blocks acquiring the lock it is not

// safepoint-safe and so will prevent a safepoint from being reached. If used

// in the wrong way this can lead to a deadlock with the safepoint code.

void Monitor::lock_without_safepoint_check(Thread * self) {

  check_safepoint_state(self, false);

  assert(_owner != self, "invariant");

  _lock.lock();

  assert_owner(NULL);

  set_owner(self);

}

void Monitor::lock_without_safepoint_check() {

  lock_without_safepoint_check(Thread::current());

}

// Returns true if thread succeeds in grabbing the lock, otherwise false.

bool Monitor::try_lock() {

  Thread * const self = Thread::current();

  DEBUG_ONLY(check_prelock_state(self, false);)

  if (_lock.try_lock()) {

    assert_owner(NULL);

    set_owner(self);

    return true;

  }

  return false;

}

void Monitor::release_for_safepoint() {

  assert_owner(NULL);

  _lock.unlock();

}

void Monitor::unlock() {

  assert_owner(Thread::current());

  set_owner(NULL);

  _lock.unlock();

}

void Monitor::notify() {

  assert_owner(Thread::current());

  _lock.notify();

}

void Monitor::notify_all() {

  assert_owner(Thread::current());

  _lock.notify_all();

}

#ifdef ASSERT

void Monitor::assert_wait_lock_state(Thread* self) {

  Monitor* least = get_least_ranked_lock_besides_this(self->owned_locks());

  assert(least != this, "Specification of get_least_... call above");

  if (least != NULL && least->rank() <= special) {

    ::tty->print("Attempting to wait on monitor %s/%d while holding"

               " lock %s/%d -- possible deadlock",

               name(), rank(), least->name(), least->rank());

    assert(false, "Shouldn't block(wait) while holding a lock of rank special");

  }

}

#endif // ASSERT

bool Monitor::wait_without_safepoint_check(long timeout) {

  Thread* const self = Thread::current();

  check_safepoint_state(self, false);

  // timeout is in milliseconds - with zero meaning never timeout

  assert(timeout >= 0, "negative timeout");

  assert_owner(self);

  assert_wait_lock_state(self);

  // conceptually set the owner to NULL in anticipation of

  // abdicating the lock in wait

  set_owner(NULL);

  int wait_status = _lock.wait(timeout);

  set_owner(self);

  return wait_status != 0;          // return true IFF timeout

}

bool Monitor::wait(long timeout, bool as_suspend_equivalent) {

  Thread* const self = Thread::current();

  check_safepoint_state(self, true);

  // timeout is in milliseconds - with zero meaning never timeout

  assert(timeout >= 0, "negative timeout");

  assert_owner(self);

  // Safepoint checking logically implies java_thread

  guarantee(self->is_Java_thread(), "invariant");

  assert_wait_lock_state(self);

#ifdef CHECK_UNHANDLED_OOPS

  // Clear unhandled oops in JavaThreads so we get a crash right away.

  self->clear_unhandled_oops();

#endif // CHECK_UNHANDLED_OOPS

  int wait_status;

  // conceptually set the owner to NULL in anticipation of

  // abdicating the lock in wait

  set_owner(NULL);

  JavaThread *jt = (JavaThread *)self;

  Monitor* in_flight_monitor = NULL;

  {

    ThreadBlockInVMWithDeadlockCheck tbivmdc(jt, &in_flight_monitor);

    OSThreadWaitState osts(self->osthread(), false /* not Object.wait() */);

    if (as_suspend_equivalent) {

      jt->set_suspend_equivalent();

      // cleared by handle_special_suspend_equivalent_condition() or

      // java_suspend_self()

    }

    wait_status = _lock.wait(timeout);

    in_flight_monitor = this;  // save for ~ThreadBlockInVMWithDeadlockCheck

    // were we externally suspended while we were waiting?

    if (as_suspend_equivalent && jt->handle_special_suspend_equivalent_condition()) {

      // Our event wait has finished and we own the lock, but

      // while we were waiting another thread suspended us. We don't

      // want to hold the lock while suspended because that

      // would surprise the thread that suspended us.

      _lock.unlock();

      jt->java_suspend_self();

      _lock.lock();

    }

  }

  if (in_flight_monitor != NULL) {

    // Not unlocked by ~ThreadBlockInVMWithDeadlockCheck

    assert_owner(NULL);

    // Conceptually reestablish ownership of the lock.

    set_owner(self);

  } else {

    lock(self);

  }

  return wait_status != 0;          // return true IFF timeout

}

// Temporary JVM_RawMonitor* support.

// Yet another degenerate version of Monitor::lock() or lock_without_safepoint_check()

// jvm_raw_lock() and _unlock() can be called by non-Java threads via JVM_RawMonitorEnter.

// There's no expectation that JVM_RawMonitors will interoperate properly with the native

// Mutex-Monitor constructs.  We happen to implement JVM_RawMonitors in terms of

// native Mutex-Monitors simply as a matter of convenience.

void Monitor::jvm_raw_lock() {

  _lock.lock();

  assert_owner(NULL);

}

void Monitor::jvm_raw_unlock() {

  assert_owner(NULL);

  _lock.unlock();

}

Monitor::~Monitor() {

  assert_owner(NULL);

}

void Monitor::ClearMonitor(Monitor * m, const char *name) {

  m->_owner             = NULL;

  if (name == NULL) {

    strcpy(m->_name, "UNKNOWN");

  } else {

    strncpy(m->_name, name, MONITOR_NAME_LEN - 1);

    m->_name[MONITOR_NAME_LEN - 1] = '\0';

  }

}

Monitor::Monitor() {

  assert(os::mutex_init_done(), "Too early!");

  ClearMonitor(this);

}

// Only Threads_lock, Heap_lock and SR_lock may be safepoint_check_sometimes.

bool is_sometimes_ok(const char* name) {

  return (strcmp(name, "Threads_lock") == 0 || strcmp(name, "Heap_lock") == 0 || strcmp(name, "SR_lock") == 0);

}

Monitor::Monitor(int Rank, const char * name, bool allow_vm_block,

                 SafepointCheckRequired safepoint_check_required) {

  assert(os::mutex_init_done(), "Too early!");

  ClearMonitor(this, name);

#ifdef ASSERT

  _allow_vm_block  = allow_vm_block;

  _rank            = Rank;

  NOT_PRODUCT(_safepoint_check_required = safepoint_check_required;)

  assert(_safepoint_check_required != Monitor::_safepoint_check_sometimes || is_sometimes_ok(name),

         "Lock has _safepoint_check_sometimes %s", name);

#endif

}

Mutex::Mutex(int Rank, const char * name, bool allow_vm_block,

             SafepointCheckRequired safepoint_check_required) {

  ClearMonitor((Monitor *) this, name);

#ifdef ASSERT

  _allow_vm_block   = allow_vm_block;

  _rank             = Rank;

  NOT_PRODUCT(_safepoint_check_required = safepoint_check_required;)

  assert(_safepoint_check_required != Monitor::_safepoint_check_sometimes || is_sometimes_ok(name),

         "Lock has _safepoint_check_sometimes %s", name);

#endif

}

bool Monitor::owned_by_self() const {

  return _owner == Thread::current();

}

void Monitor::print_on_error(outputStream* st) const {

  st->print("[" PTR_FORMAT, p2i(this));

  st->print("] %s", _name);

  st->print(" - owner thread: " PTR_FORMAT, p2i(_owner));

}

// ----------------------------------------------------------------------------------

// Non-product code

#ifndef PRODUCT

void Monitor::print_on(outputStream* st) const {

  st->print_cr("Mutex: [" PTR_FORMAT "] %s - owner: " PTR_FORMAT,

               p2i(this), _name, p2i(_owner));

}

#endif

#ifndef PRODUCT

#ifdef ASSERT

void Monitor::assert_owner(Thread * expected) {

  const char* msg = "invalid owner";

  if (expected == NULL) {

    msg = "should be un-owned";

  }

  else if (expected == Thread::current()) {

    msg = "should be owned by current thread";

  }

  assert(_owner == expected,

         "%s: owner=" INTPTR_FORMAT ", should be=" INTPTR_FORMAT,

         msg, p2i(_owner), p2i(expected));

}

Monitor * Monitor::get_least_ranked_lock(Monitor * locks) {

  Monitor *res, *tmp;

  for (res = tmp = locks; tmp != NULL; tmp = tmp->next()) {

    if (tmp->rank() < res->rank()) {

      res = tmp;

    }

  }

  if (!SafepointSynchronize::is_at_safepoint()) {

    // In this case, we expect the held locks to be

    // in increasing rank order (modulo any native ranks)

    for (tmp = locks; tmp != NULL; tmp = tmp->next()) {

      if (tmp->next() != NULL) {

        assert(tmp->rank() == Mutex::native ||

               tmp->rank() <= tmp->next()->rank(), "mutex rank anomaly?");

      }

    }

  }

  return res;

}

Monitor* Monitor::get_least_ranked_lock_besides_this(Monitor* locks) {

  Monitor *res, *tmp;

  for (res = NULL, tmp = locks; tmp != NULL; tmp = tmp->next()) {

    if (tmp != this && (res == NULL || tmp->rank() < res->rank())) {

      res = tmp;

    }

  }

  if (!SafepointSynchronize::is_at_safepoint()) {

    // In this case, we expect the held locks to be

    // in increasing rank order (modulo any native ranks)

    for (tmp = locks; tmp != NULL; tmp = tmp->next()) {

      if (tmp->next() != NULL) {

        assert(tmp->rank() == Mutex::native ||

               tmp->rank() <= tmp->next()->rank(), "mutex rank anomaly?");

      }

    }

  }

  return res;

}

bool Monitor::contains(Monitor* locks, Monitor * lock) {

  for (; locks != NULL; locks = locks->next()) {

    if (locks == lock) {

      return true;

    }

  }

  return false;

}

#endif

// Called immediately after lock acquisition or release as a diagnostic

// to track the lock-set of the thread and test for rank violations that

// might indicate exposure to deadlock.

// Rather like an EventListener for _owner (:>).

void Monitor::set_owner_implementation(Thread *new_owner) {

  // This function is solely responsible for maintaining

  // and checking the invariant that threads and locks

  // are in a 1/N relation, with some some locks unowned.

  // It uses the Mutex::_owner, Mutex::_next, and

  // Thread::_owned_locks fields, and no other function

  // changes those fields.

  // It is illegal to set the mutex from one non-NULL

  // owner to another--it must be owned by NULL as an

  // intermediate state.

  if (new_owner != NULL) {

    // the thread is acquiring this lock

    assert(new_owner == Thread::current(), "Should I be doing this?");

    assert(_owner == NULL, "setting the owner thread of an already owned mutex");

    _owner = new_owner; // set the owner

    // link "this" into the owned locks list

#ifdef ASSERT  // Thread::_owned_locks is under the same ifdef

    Monitor* locks = get_least_ranked_lock(new_owner->owned_locks());

    // Mutex::set_owner_implementation is a friend of Thread

    assert(this->rank() >= 0, "bad lock rank");

    // Deadlock avoidance rules require us to acquire Mutexes only in

    // a global total order. For example m1 is the lowest ranked mutex

    // that the thread holds and m2 is the mutex the thread is trying

    // to acquire, then deadlock avoidance rules require that the rank

    // of m2 be less than the rank of m1.

    // The rank Mutex::native  is an exception in that it is not subject

    // to the verification rules.

    if (this->rank() != Mutex::native &&

        this->rank() != Mutex::suspend_resume &&

        locks != NULL && locks->rank() <= this->rank() &&

        !SafepointSynchronize::is_at_safepoint()) {

      new_owner->print_owned_locks();

      fatal("acquiring lock %s/%d out of order with lock %s/%d -- "

            "possible deadlock", this->name(), this->rank(),

            locks->name(), locks->rank());

    }

    this->_next = new_owner->_owned_locks;

    new_owner->_owned_locks = this;

#endif

  } else {

    // the thread is releasing this lock

    Thread* old_owner = _owner;

    DEBUG_ONLY(_last_owner = old_owner;)

    assert(old_owner != NULL, "removing the owner thread of an unowned mutex");

    assert(old_owner == Thread::current(), "removing the owner thread of an unowned mutex");

    _owner = NULL; // set the owner

#ifdef ASSERT

    Monitor *locks = old_owner->owned_locks();

    // remove "this" from the owned locks list

    Monitor *prev = NULL;

    bool found = false;

    for (; locks != NULL; prev = locks, locks = locks->next()) {

      if (locks == this) {

        found = true;

        break;

      }

    }

    assert(found, "Removing a lock not owned");

    if (prev == NULL) {

      old_owner->_owned_locks = _next;

    } else {

      prev->_next = _next;

    }

    _next = NULL;

#endif

  }

}

// Factored out common sanity checks for locking mutex'es. Used by lock() and try_lock()

void Monitor::check_prelock_state(Thread *thread, bool safepoint_check) {

  if (safepoint_check) {

    assert((!thread->is_Java_thread() || ((JavaThread *)thread)->thread_state() == _thread_in_vm)

           || rank() == Mutex::special, "wrong thread state for using locks");

    if (thread->is_VM_thread() && !allow_vm_block()) {

      fatal("VM thread using lock %s (not allowed to block on)", name());

    }

    DEBUG_ONLY(if (rank() != Mutex::special) \

               thread->check_for_valid_safepoint_state(false);)

  }

  assert(!os::ThreadCrashProtection::is_crash_protected(thread),

         "locking not allowed when crash protection is set");