/*
* Copyright (c) 2001, 2011, 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 "memory/allocation.hpp"
#include "memory/allocation.inline.hpp"
#include "runtime/os.hpp"
#include "utilities/workgroup.hpp"
// Definitions of WorkGang methods.
AbstractWorkGang::AbstractWorkGang(const char* name,
bool are_GC_task_threads,
bool are_ConcurrentGC_threads) :
_name(name),
_are_GC_task_threads(are_GC_task_threads),
_are_ConcurrentGC_threads(are_ConcurrentGC_threads) {
assert(!(are_GC_task_threads && are_ConcurrentGC_threads),
"They cannot both be STW GC and Concurrent threads" );
// Other initialization.
_monitor = new Monitor(/* priority */ Mutex::leaf,
/* name */ "WorkGroup monitor",
/* allow_vm_block */ are_GC_task_threads);
assert(monitor() != NULL, "Failed to allocate monitor");
_terminate = false;
_task = NULL;
_sequence_number = 0;
_started_workers = 0;
_finished_workers = 0;
}
WorkGang::WorkGang(const char* name,
uint workers,
bool are_GC_task_threads,
bool are_ConcurrentGC_threads) :
AbstractWorkGang(name, are_GC_task_threads, are_ConcurrentGC_threads) {
_total_workers = workers;
}
GangWorker* WorkGang::allocate_worker(uint which) {
GangWorker* new_worker = new GangWorker(this, which);
return new_worker;
}
// The current implementation will exit if the allocation
// of any worker fails. Still, return a boolean so that
// a future implementation can possibly do a partial
// initialization of the workers and report such to the
// caller.
bool WorkGang::initialize_workers() {
if (TraceWorkGang) {
tty->print_cr("Constructing work gang %s with %d threads",
name(),
total_workers());
}
_gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, total_workers(), mtInternal);
if (gang_workers() == NULL) {
vm_exit_out_of_memory(0, "Cannot create GangWorker array.");
return false;
}
os::ThreadType worker_type;
if (are_ConcurrentGC_threads()) {
worker_type = os::cgc_thread;
} else {
worker_type = os::pgc_thread;
}
for (uint worker = 0; worker < total_workers(); worker += 1) {
GangWorker* new_worker = allocate_worker(worker);
assert(new_worker != NULL, "Failed to allocate GangWorker");
_gang_workers[worker] = new_worker;
if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {
vm_exit_out_of_memory(0, "Cannot create worker GC thread. Out of system resources.");
return false;
}
if (!DisableStartThread) {
os::start_thread(new_worker);
}
}
return true;
}
AbstractWorkGang::~AbstractWorkGang() {
if (TraceWorkGang) {
tty->print_cr("Destructing work gang %s", name());
}
stop(); // stop all the workers
for (uint worker = 0; worker < total_workers(); worker += 1) {
delete gang_worker(worker);
}
delete gang_workers();
delete monitor();
}
GangWorker* AbstractWorkGang::gang_worker(uint i) const {
// Array index bounds checking.
GangWorker* result = NULL;
assert(gang_workers() != NULL, "No workers for indexing");
assert(((i >= 0) && (i < total_workers())), "Worker index out of bounds");
result = _gang_workers[i];
assert(result != NULL, "Indexing to null worker");
return result;
}
void WorkGang::run_task(AbstractGangTask* task) {
run_task(task, total_workers());
}
void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {
task->set_for_termination(no_of_parallel_workers);
// This thread is executed by the VM thread which does not block
// on ordinary MutexLocker's.
MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
if (TraceWorkGang) {
tty->print_cr("Running work gang %s task %s", name(), task->name());
}
// Tell all the workers to run a task.
assert(task != NULL, "Running a null task");
// Initialize.
_task = task;
_sequence_number += 1;
_started_workers = 0;
_finished_workers = 0;
// Tell the workers to get to work.
monitor()->notify_all();
// Wait for them to be finished
while (finished_workers() < no_of_parallel_workers) {
if (TraceWorkGang) {
tty->print_cr("Waiting in work gang %s: %d/%d finished sequence %d",
name(), finished_workers(), no_of_parallel_workers,
_sequence_number);
}
monitor()->wait(/* no_safepoint_check */ true);
}
_task = NULL;
if (TraceWorkGang) {
tty->print_cr("\nFinished work gang %s: %d/%d sequence %d",
name(), finished_workers(), no_of_parallel_workers,
_sequence_number);
Thread* me = Thread::current();
tty->print_cr(" T: 0x%x VM_thread: %d", me, me->is_VM_thread());
}
}
void FlexibleWorkGang::run_task(AbstractGangTask* task) {
// If active_workers() is passed, _finished_workers
// must only be incremented for workers that find non_null
// work (as opposed to all those that just check that the
// task is not null).
WorkGang::run_task(task, (uint) active_workers());
}
void AbstractWorkGang::stop() {
// Tell all workers to terminate, then wait for them to become inactive.
MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);
if (TraceWorkGang) {
tty->print_cr("Stopping work gang %s task %s", name(), task()->name());
}
_task = NULL;
_terminate = true;
monitor()->notify_all();
while (finished_workers() < active_workers()) {
if (TraceWorkGang) {
tty->print_cr("Waiting in work gang %s: %d/%d finished",
name(), finished_workers(), active_workers());
}
monitor()->wait(/* no_safepoint_check */ true);
}
}
void AbstractWorkGang::internal_worker_poll(WorkData* data) const {
assert(monitor()->owned_by_self(), "worker_poll is an internal method");
assert(data != NULL, "worker data is null");
data->set_terminate(terminate());
data->set_task(task());
data->set_sequence_number(sequence_number());
}
void AbstractWorkGang::internal_note_start() {
assert(monitor()->owned_by_self(), "note_finish is an internal method");
_started_workers += 1;
}
void AbstractWorkGang::internal_note_finish() {
assert(monitor()->owned_by_self(), "note_finish is an internal method");
_finished_workers += 1;
}
void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {
uint num_thr = total_workers();
for (uint i = 0; i < num_thr; i++) {
gang_worker(i)->print_on(st);
st->cr();
}
}
void AbstractWorkGang::threads_do(ThreadClosure* tc) const {
assert(tc != NULL, "Null ThreadClosure");
uint num_thr = total_workers();
for (uint i = 0; i < num_thr; i++) {
tc->do_thread(gang_worker(i));
}
}
// GangWorker methods.
GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {
_gang = gang;
set_id(id);
set_name("Gang worker#%d (%s)", id, gang->name());
}
void GangWorker::run() {
initialize();
loop();
}
void GangWorker::initialize() {
this->initialize_thread_local_storage();
this->record_stack_base_and_size();
assert(_gang != NULL, "No gang to run in");
os::set_priority(this, NearMaxPriority);
if (TraceWorkGang) {
tty->print_cr("Running gang worker for gang %s id %d",
gang()->name(), id());
}
// The VM thread should not execute here because MutexLocker's are used
// as (opposed to MutexLockerEx's).
assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"
" of a work gang");
}
void GangWorker::loop() {
int previous_sequence_number = 0;
Monitor* gang_monitor = gang()->monitor();
for ( ; /* !terminate() */; ) {
WorkData data;
int part; // Initialized below.
{
// Grab the gang mutex.
MutexLocker ml(gang_monitor);
// Wait for something to do.
// Polling outside the while { wait } avoids missed notifies
// in the outer loop.
gang()->internal_worker_poll(&data);
if (TraceWorkGang) {
tty->print("Polled outside for work in gang %s worker %d",
gang()->name(), id());
tty->print(" terminate: %s",
data.terminate() ? "true" : "false");
tty->print(" sequence: %d (prev: %d)",
data.sequence_number(), previous_sequence_number);
if (data.task() != NULL) {
tty->print(" task: %s", data.task()->name());
} else {
tty->print(" task: NULL");
}
tty->cr();
}
for ( ; /* break or return */; ) {
// Terminate if requested.
if (data.terminate()) {
gang()->internal_note_finish();
gang_monitor->notify_all();
return;
}
// Check for new work.
if ((data.task() != NULL) &&
(data.sequence_number() != previous_sequence_number)) {
if (gang()->needs_more_workers()) {
gang()->internal_note_start();
gang_monitor->notify_all();
part = gang()->started_workers() - 1;
break;
}
}
// Nothing to do.
gang_monitor->wait(/* no_safepoint_check */ true);
gang()->internal_worker_poll(&data);
if (TraceWorkGang) {
tty->print("Polled inside for work in gang %s worker %d",
gang()->name(), id());
tty->print(" terminate: %s",
data.terminate() ? "true" : "false");
tty->print(" sequence: %d (prev: %d)",
data.sequence_number(), previous_sequence_number);
if (data.task() != NULL) {
tty->print(" task: %s", data.task()->name());
} else {
tty->print(" task: NULL");
}
tty->cr();
}
}
// Drop gang mutex.
}
if (TraceWorkGang) {
tty->print("Work for work gang %s id %d task %s part %d",
gang()->name(), id(), data.task()->name(), part);
}
assert(data.task() != NULL, "Got null task");
data.task()->work(part);
{
if (TraceWorkGang) {
tty->print("Finish for work gang %s id %d task %s part %d",
gang()->name(), id(), data.task()->name(), part);
}
// Grab the gang mutex.
MutexLocker ml(gang_monitor);
gang()->internal_note_finish();
// Tell the gang you are done.
gang_monitor->notify_all();
// Drop the gang mutex.
}
previous_sequence_number = data.sequence_number();
}
}
bool GangWorker::is_GC_task_thread() const {
return gang()->are_GC_task_threads();
}
bool GangWorker::is_ConcurrentGC_thread() const {
return gang()->are_ConcurrentGC_threads();
}
void GangWorker::print_on(outputStream* st) const {
st->print("\"%s\" ", name());
Thread::print_on(st);
st->cr();
}
// Printing methods
const char* AbstractWorkGang::name() const {
return _name;
}
#ifndef PRODUCT
const char* AbstractGangTask::name() const {
return _name;
}
#endif /* PRODUCT */
// FlexibleWorkGang
// *** WorkGangBarrierSync
WorkGangBarrierSync::WorkGangBarrierSync()
: _monitor(Mutex::safepoint, "work gang barrier sync", true),
_n_workers(0), _n_completed(0), _should_reset(false) {
}
WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)
: _monitor(Mutex::safepoint, name, true),
_n_workers(n_workers), _n_completed(0), _should_reset(false) {
}
void WorkGangBarrierSync::set_n_workers(uint n_workers) {
_n_workers = n_workers;
_n_completed = 0;
_should_reset = false;
}
void WorkGangBarrierSync::enter() {
MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);
if (should_reset()) {
// The should_reset() was set and we are the first worker to enter
// the sync barrier. We will zero the n_completed() count which
// effectively resets the barrier.
zero_completed();
set_should_reset(false);
}
inc_completed();
if (n_completed() == n_workers()) {
// At this point we would like to reset the barrier to be ready in
// case it is used again. However, we cannot set n_completed() to
// 0, even after the notify_all(), given that some other workers
// might still be waiting for n_completed() to become ==
// n_workers(). So, if we set n_completed() to 0, those workers
// will get stuck (as they will wake up, see that n_completed() !=
// n_workers() and go back to sleep). Instead, we raise the
// should_reset() flag and the barrier will be reset the first
// time a worker enters it again.
set_should_reset(true);
monitor()->notify_all();
} else {
while (n_completed() != n_workers()) {
monitor()->wait(/* no_safepoint_check */ true);
}
}
}
// SubTasksDone functions.
SubTasksDone::SubTasksDone(uint n) :
_n_tasks(n), _n_threads(1), _tasks(NULL) {
_tasks = NEW_C_HEAP_ARRAY(uint, n, mtInternal);
guarantee(_tasks != NULL, "alloc failure");
clear();
}
bool SubTasksDone::valid() {
return _tasks != NULL;
}
void SubTasksDone::set_n_threads(uint t) {
assert(_claimed == 0 || _threads_completed == _n_threads,
"should not be called while tasks are being processed!");
_n_threads = (t == 0 ? 1 : t);
}
void SubTasksDone::clear() {
for (uint i = 0; i < _n_tasks; i++) {
_tasks[i] = 0;
}
_threads_completed = 0;
#ifdef ASSERT
_claimed = 0;
#endif
}
bool SubTasksDone::is_task_claimed(uint t) {
assert(0 <= t && t < _n_tasks, "bad task id.");
uint old = _tasks[t];
if (old == 0) {
old = Atomic::cmpxchg(1, &_tasks[t], 0);
}
assert(_tasks[t] == 1, "What else?");
bool res = old != 0;
#ifdef ASSERT
if (!res) {
assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");
Atomic::inc((volatile jint*) &_claimed);
}
#endif
return res;
}
void SubTasksDone::all_tasks_completed() {
jint observed = _threads_completed;
jint old;
do {
old = observed;
observed = Atomic::cmpxchg(old+1, &_threads_completed, old);
} while (observed != old);
// If this was the last thread checking in, clear the tasks.
if (observed+1 == (jint)_n_threads) clear();
}
SubTasksDone::~SubTasksDone() {
if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks, mtInternal);
}
// *** SequentialSubTasksDone
void SequentialSubTasksDone::clear() {
_n_tasks = _n_claimed = 0;
_n_threads = _n_completed = 0;
}
bool SequentialSubTasksDone::valid() {
return _n_threads > 0;
}
bool SequentialSubTasksDone::is_task_claimed(uint& t) {
uint* n_claimed_ptr = &_n_claimed;
t = *n_claimed_ptr;
while (t < _n_tasks) {
jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);
if (res == (jint)t) {
return false;
}
t = *n_claimed_ptr;
}
return true;
}
bool SequentialSubTasksDone::all_tasks_completed() {
uint* n_completed_ptr = &_n_completed;
uint complete = *n_completed_ptr;
while (true) {
uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);
if (res == complete) {
break;
}
complete = res;
}
if (complete+1 == _n_threads) {
clear();
return true;
}
return false;
}
bool FreeIdSet::_stat_init = false;
FreeIdSet* FreeIdSet::_sets[NSets];
bool FreeIdSet::_safepoint;
FreeIdSet::FreeIdSet(int sz, Monitor* mon) :
_sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)
{
_ids = new int[sz];
for (int i = 0; i < sz; i++) _ids[i] = i+1;
_ids[sz-1] = end_of_list; // end of list.
if (_stat_init) {
for (int j = 0; j < NSets; j++) _sets[j] = NULL;
_stat_init = true;
}
// Add to sets. (This should happen while the system is still single-threaded.)
for (int j = 0; j < NSets; j++) {
if (_sets[j] == NULL) {
_sets[j] = this;
_index = j;
break;
}
}
guarantee(_index != -1, "Too many FreeIdSets in use!");
}
FreeIdSet::~FreeIdSet() {
_sets[_index] = NULL;
}
void FreeIdSet::set_safepoint(bool b) {
_safepoint = b;
if (b) {
for (int j = 0; j < NSets; j++) {
if (_sets[j] != NULL && _sets[j]->_waiters > 0) {
Monitor* mon = _sets[j]->_mon;
mon->lock_without_safepoint_check();
mon->notify_all();
mon->unlock();
}
}
}
}
#define FID_STATS 0
int FreeIdSet::claim_par_id() {
#if FID_STATS
thread_t tslf = thr_self();
tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);
#endif
MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
while (!_safepoint && _hd == end_of_list) {
_waiters++;
#if FID_STATS
if (_waiters > 5) {
tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",
tslf, _waiters, _claimed);
}
#endif
_mon->wait(Mutex::_no_safepoint_check_flag);
_waiters--;
}
if (_hd == end_of_list) {
#if FID_STATS
tty->print("claim_par_id[%d]: returning EOL.\n", tslf);
#endif
return -1;
} else {
int res = _hd;
_hd = _ids[res];
_ids[res] = claimed; // For debugging.
_claimed++;
#if FID_STATS
tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",
tslf, res, _claimed);
#endif
return res;
}
}
bool FreeIdSet::claim_perm_id(int i) {
assert(0 <= i && i < _sz, "Out of range.");
MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
int prev = end_of_list;
int cur = _hd;
while (cur != end_of_list) {
if (cur == i) {
if (prev == end_of_list) {
_hd = _ids[cur];
} else {
_ids[prev] = _ids[cur];
}
_ids[cur] = claimed;
_claimed++;
return true;
} else {
prev = cur;
cur = _ids[cur];
}
}
return false;
}
void FreeIdSet::release_par_id(int id) {
MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);
assert(_ids[id] == claimed, "Precondition.");
_ids[id] = _hd;
_hd = id;
_claimed--;
#if FID_STATS
tty->print("[%d] release_par_id(%d), waiters =%d, claimed = %d.\n",
thr_self(), id, _waiters, _claimed);
#endif
if (_waiters > 0)
// Notify all would be safer, but this is OK, right?
_mon->notify_all();
}