| /* |
| * Copyright (c) 2005, 2013, 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 "utilities/macros.hpp" |
| #include "utilities/yieldingWorkgroup.hpp" |
| |
| // Forward declaration of classes declared here. |
| |
| class GangWorker; |
| class WorkData; |
| |
| YieldingFlexibleWorkGang::YieldingFlexibleWorkGang( |
| const char* name, uint workers, bool are_GC_task_threads) : |
| FlexibleWorkGang(name, workers, are_GC_task_threads, false), |
| _yielded_workers(0) {} |
| |
| GangWorker* YieldingFlexibleWorkGang::allocate_worker(uint which) { |
| YieldingFlexibleGangWorker* new_member = |
| new YieldingFlexibleGangWorker(this, which); |
| return (YieldingFlexibleGangWorker*) new_member; |
| } |
| |
| // Run a task; returns when the task is done, or the workers yield, |
| // or the task is aborted, or the work gang is terminated via stop(). |
| // A task that has been yielded can be continued via this interface |
| // by using the same task repeatedly as the argument to the call. |
| // It is expected that the YieldingFlexibleGangTask carries the appropriate |
| // continuation information used by workers to continue the task |
| // from its last yield point. Thus, a completed task will return |
| // immediately with no actual work having been done by the workers. |
| ///////////////////// |
| // Implementatiuon notes: remove before checking XXX |
| /* |
| Each gang is working on a task at a certain time. |
| Some subset of workers may have yielded and some may |
| have finished their quota of work. Until this task has |
| been completed, the workers are bound to that task. |
| Once the task has been completed, the gang unbounds |
| itself from the task. |
| |
| The yielding work gang thus exports two invokation |
| interfaces: run_task() and continue_task(). The |
| first is used to initiate a new task and bind it |
| to the workers; the second is used to continue an |
| already bound task that has yielded. Upon completion |
| the binding is released and a new binding may be |
| created. |
| |
| The shape of a yielding work gang is as follows: |
| |
| Overseer invokes run_task(*task). |
| Lock gang monitor |
| Check that there is no existing binding for the gang |
| If so, abort with an error |
| Else, create a new binding of this gang to the given task |
| Set number of active workers (as asked) |
| Notify workers that work is ready to be done |
| [the requisite # workers would then start up |
| and do the task] |
| Wait on the monitor until either |
| all work is completed or the task has yielded |
| -- this is normally done through |
| yielded + completed == active |
| [completed workers are rest to idle state by overseer?] |
| return appropriate status to caller |
| |
| Overseer invokes continue_task(*task), |
| Lock gang monitor |
| Check that task is the same as current binding |
| If not, abort with an error |
| Else, set the number of active workers as requested? |
| Notify workers that they can continue from yield points |
| New workers can also start up as required |
| while satisfying the constraint that |
| active + yielded does not exceed required number |
| Wait (as above). |
| |
| NOTE: In the above, for simplicity in a first iteration |
| our gangs will be of fixed population and will not |
| therefore be flexible work gangs, just yielding work |
| gangs. Once this works well, we will in a second |
| iteration.refinement introduce flexibility into |
| the work gang. |
| |
| NOTE: we can always create a new gang per each iteration |
| in order to get the flexibility, but we will for now |
| desist that simplified route. |
| |
| */ |
| ///////////////////// |
| void YieldingFlexibleWorkGang::start_task(YieldingFlexibleGangTask* new_task) { |
| MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
| assert(task() == NULL, "Gang currently tied to a task"); |
| assert(new_task != NULL, "Null task"); |
| // Bind task to gang |
| _task = new_task; |
| new_task->set_gang(this); // Establish 2-way binding to support yielding |
| _sequence_number++; |
| |
| uint requested_size = new_task->requested_size(); |
| assert(requested_size >= 0, "Should be non-negative"); |
| if (requested_size != 0) { |
| _active_workers = MIN2(requested_size, total_workers()); |
| } else { |
| _active_workers = active_workers(); |
| } |
| new_task->set_actual_size(_active_workers); |
| new_task->set_for_termination(_active_workers); |
| |
| assert(_started_workers == 0, "Tabula rasa non"); |
| assert(_finished_workers == 0, "Tabula rasa non"); |
| assert(_yielded_workers == 0, "Tabula rasa non"); |
| yielding_task()->set_status(ACTIVE); |
| |
| // Wake up all the workers, the first few will get to work, |
| // and the rest will go back to sleep |
| monitor()->notify_all(); |
| wait_for_gang(); |
| } |
| |
| void YieldingFlexibleWorkGang::wait_for_gang() { |
| |
| assert(monitor()->owned_by_self(), "Data race"); |
| // Wait for task to complete or yield |
| for (Status status = yielding_task()->status(); |
| status != COMPLETED && status != YIELDED && status != ABORTED; |
| status = yielding_task()->status()) { |
| assert(started_workers() <= active_workers(), "invariant"); |
| assert(finished_workers() <= active_workers(), "invariant"); |
| assert(yielded_workers() <= active_workers(), "invariant"); |
| monitor()->wait(Mutex::_no_safepoint_check_flag); |
| } |
| switch (yielding_task()->status()) { |
| case COMPLETED: |
| case ABORTED: { |
| assert(finished_workers() == active_workers(), "Inconsistent status"); |
| assert(yielded_workers() == 0, "Invariant"); |
| reset(); // for next task; gang<->task binding released |
| break; |
| } |
| case YIELDED: { |
| assert(yielded_workers() > 0, "Invariant"); |
| assert(yielded_workers() + finished_workers() == active_workers(), |
| "Inconsistent counts"); |
| break; |
| } |
| case ACTIVE: |
| case INACTIVE: |
| case COMPLETING: |
| case YIELDING: |
| case ABORTING: |
| default: |
| ShouldNotReachHere(); |
| } |
| } |
| |
| void YieldingFlexibleWorkGang::continue_task( |
| YieldingFlexibleGangTask* gang_task) { |
| |
| MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
| assert(task() != NULL && task() == gang_task, "Incorrect usage"); |
| assert(_started_workers == _active_workers, "Precondition"); |
| assert(_yielded_workers > 0 && yielding_task()->status() == YIELDED, |
| "Else why are we calling continue_task()"); |
| // Restart the yielded gang workers |
| yielding_task()->set_status(ACTIVE); |
| monitor()->notify_all(); |
| wait_for_gang(); |
| } |
| |
| void YieldingFlexibleWorkGang::reset() { |
| _started_workers = 0; |
| _finished_workers = 0; |
| yielding_task()->set_gang(NULL); |
| _task = NULL; // unbind gang from task |
| } |
| |
| void YieldingFlexibleWorkGang::yield() { |
| assert(task() != NULL, "Inconsistency; should have task binding"); |
| MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
| assert(yielded_workers() < active_workers(), "Consistency check"); |
| if (yielding_task()->status() == ABORTING) { |
| // Do not yield; we need to abort as soon as possible |
| // XXX NOTE: This can cause a performance pathology in the |
| // current implementation in Mustang, as of today, and |
| // pre-Mustang in that as soon as an overflow occurs, |
| // yields will not be honoured. The right way to proceed |
| // of course is to fix bug # TBF, so that abort's cause |
| // us to return at each potential yield point. |
| return; |
| } |
| if (++_yielded_workers + finished_workers() == active_workers()) { |
| yielding_task()->set_status(YIELDED); |
| monitor()->notify_all(); |
| } else { |
| yielding_task()->set_status(YIELDING); |
| } |
| |
| while (true) { |
| switch (yielding_task()->status()) { |
| case YIELDING: |
| case YIELDED: { |
| monitor()->wait(Mutex::_no_safepoint_check_flag); |
| break; // from switch |
| } |
| case ACTIVE: |
| case ABORTING: |
| case COMPLETING: { |
| assert(_yielded_workers > 0, "Else why am i here?"); |
| _yielded_workers--; |
| return; |
| } |
| case INACTIVE: |
| case ABORTED: |
| case COMPLETED: |
| default: { |
| ShouldNotReachHere(); |
| } |
| } |
| } |
| // Only return is from inside switch statement above |
| ShouldNotReachHere(); |
| } |
| |
| void YieldingFlexibleWorkGang::abort() { |
| assert(task() != NULL, "Inconsistency; should have task binding"); |
| MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
| assert(yielded_workers() < active_workers(), "Consistency check"); |
| #ifndef PRODUCT |
| switch (yielding_task()->status()) { |
| // allowed states |
| case ACTIVE: |
| case ABORTING: |
| case COMPLETING: |
| case YIELDING: |
| break; |
| // not allowed states |
| case INACTIVE: |
| case ABORTED: |
| case COMPLETED: |
| case YIELDED: |
| default: |
| ShouldNotReachHere(); |
| } |
| #endif // !PRODUCT |
| Status prev_status = yielding_task()->status(); |
| yielding_task()->set_status(ABORTING); |
| if (prev_status == YIELDING) { |
| assert(yielded_workers() > 0, "Inconsistency"); |
| // At least one thread has yielded, wake it up |
| // so it can go back to waiting stations ASAP. |
| monitor()->notify_all(); |
| } |
| } |
| |
| /////////////////////////////// |
| // YieldingFlexibleGangTask |
| /////////////////////////////// |
| void YieldingFlexibleGangTask::yield() { |
| assert(gang() != NULL, "No gang to signal"); |
| gang()->yield(); |
| } |
| |
| void YieldingFlexibleGangTask::abort() { |
| assert(gang() != NULL, "No gang to signal"); |
| gang()->abort(); |
| } |
| |
| /////////////////////////////// |
| // YieldingFlexibleGangWorker |
| /////////////////////////////// |
| void YieldingFlexibleGangWorker::loop() { |
| int previous_sequence_number = 0; |
| Monitor* gang_monitor = gang()->monitor(); |
| MutexLockerEx ml(gang_monitor, Mutex::_no_safepoint_check_flag); |
| WorkData data; |
| int id; |
| while (true) { |
| // Check if there is work to do or if we have been asked |
| // to terminate |
| gang()->internal_worker_poll(&data); |
| if (data.terminate()) { |
| // We have been asked to terminate. |
| assert(gang()->task() == NULL, "No task binding"); |
| // set_status(TERMINATED); |
| return; |
| } else if (data.task() != NULL && |
| data.sequence_number() != previous_sequence_number) { |
| // There is work to be done. |
| // First check if we need to become active or if there |
| // are already the requisite number of workers |
| if (gang()->started_workers() == yf_gang()->active_workers()) { |
| // There are already enough workers, we do not need to |
| // to run; fall through and wait on monitor. |
| } else { |
| // We need to pitch in and do the work. |
| assert(gang()->started_workers() < yf_gang()->active_workers(), |
| "Unexpected state"); |
| id = gang()->started_workers(); |
| gang()->internal_note_start(); |
| // Now, release the gang mutex and do the work. |
| { |
| MutexUnlockerEx mul(gang_monitor, Mutex::_no_safepoint_check_flag); |
| data.task()->work(id); // This might include yielding |
| } |
| // Reacquire monitor and note completion of this worker |
| gang()->internal_note_finish(); |
| // Update status of task based on whether all workers have |
| // finished or some have yielded |
| assert(data.task() == gang()->task(), "Confused task binding"); |
| if (gang()->finished_workers() == yf_gang()->active_workers()) { |
| switch (data.yf_task()->status()) { |
| case ABORTING: { |
| data.yf_task()->set_status(ABORTED); |
| break; |
| } |
| case ACTIVE: |
| case COMPLETING: { |
| data.yf_task()->set_status(COMPLETED); |
| break; |
| } |
| default: |
| ShouldNotReachHere(); |
| } |
| gang_monitor->notify_all(); // Notify overseer |
| } else { // at least one worker is still working or yielded |
| assert(gang()->finished_workers() < yf_gang()->active_workers(), |
| "Counts inconsistent"); |
| switch (data.yf_task()->status()) { |
| case ACTIVE: { |
| // first, but not only thread to complete |
| data.yf_task()->set_status(COMPLETING); |
| break; |
| } |
| case YIELDING: { |
| if (gang()->finished_workers() + yf_gang()->yielded_workers() |
| == yf_gang()->active_workers()) { |
| data.yf_task()->set_status(YIELDED); |
| gang_monitor->notify_all(); // notify overseer |
| } |
| break; |
| } |
| case ABORTING: |
| case COMPLETING: { |
| break; // nothing to do |
| } |
| default: // everything else: INACTIVE, YIELDED, ABORTED, COMPLETED |
| ShouldNotReachHere(); |
| } |
| } |
| } |
| } |
| // Remember the sequence number |
| previous_sequence_number = data.sequence_number(); |
| // Wait for more work |
| gang_monitor->wait(Mutex::_no_safepoint_check_flag); |
| } |
| } |