author | jmasa |
Wed, 25 Jun 2014 20:41:16 -0700 | |
changeset 25354 | f6762819b488 |
parent 22234 | da823d78ad65 |
child 29580 | a67a581cfe11 |
permissions | -rw-r--r-- |
1 | 1 |
/* |
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* Copyright (c) 2005, 2013, Oracle and/or its affiliates. All rights reserved. |
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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* |
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* This code is free software; you can redistribute it and/or modify it |
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* under the terms of the GNU General Public License version 2 only, as |
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* published by the Free Software Foundation. |
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* |
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* This code is distributed in the hope that it will be useful, but WITHOUT |
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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* version 2 for more details (a copy is included in the LICENSE file that |
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* accompanied this code). |
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* |
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* You should have received a copy of the GNU General Public License version |
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* 2 along with this work; if not, write to the Free Software Foundation, |
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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* |
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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* or visit www.oracle.com if you need additional information or have any |
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* questions. |
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* |
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*/ |
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||
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#include "precompiled.hpp" |
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#include "utilities/macros.hpp" |
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#include "utilities/yieldingWorkgroup.hpp" |
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// Forward declaration of classes declared here. |
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class GangWorker; |
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class WorkData; |
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YieldingFlexibleWorkGang::YieldingFlexibleWorkGang( |
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const char* name, uint workers, bool are_GC_task_threads) : |
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FlexibleWorkGang(name, workers, are_GC_task_threads, false), |
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_yielded_workers(0) {} |
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GangWorker* YieldingFlexibleWorkGang::allocate_worker(uint which) { |
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YieldingFlexibleGangWorker* new_member = |
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new YieldingFlexibleGangWorker(this, which); |
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return (YieldingFlexibleGangWorker*) new_member; |
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} |
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// Run a task; returns when the task is done, or the workers yield, |
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// or the task is aborted, or the work gang is terminated via stop(). |
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// A task that has been yielded can be continued via this interface |
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// by using the same task repeatedly as the argument to the call. |
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// It is expected that the YieldingFlexibleGangTask carries the appropriate |
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// continuation information used by workers to continue the task |
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// from its last yield point. Thus, a completed task will return |
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// immediately with no actual work having been done by the workers. |
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///////////////////// |
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// Implementatiuon notes: remove before checking XXX |
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/* |
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Each gang is working on a task at a certain time. |
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Some subset of workers may have yielded and some may |
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have finished their quota of work. Until this task has |
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been completed, the workers are bound to that task. |
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Once the task has been completed, the gang unbounds |
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itself from the task. |
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||
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The yielding work gang thus exports two invokation |
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interfaces: run_task() and continue_task(). The |
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first is used to initiate a new task and bind it |
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to the workers; the second is used to continue an |
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already bound task that has yielded. Upon completion |
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the binding is released and a new binding may be |
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created. |
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||
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The shape of a yielding work gang is as follows: |
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Overseer invokes run_task(*task). |
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Lock gang monitor |
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Check that there is no existing binding for the gang |
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If so, abort with an error |
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Else, create a new binding of this gang to the given task |
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Set number of active workers (as asked) |
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Notify workers that work is ready to be done |
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[the requisite # workers would then start up |
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and do the task] |
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Wait on the monitor until either |
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all work is completed or the task has yielded |
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-- this is normally done through |
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yielded + completed == active |
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[completed workers are rest to idle state by overseer?] |
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return appropriate status to caller |
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Overseer invokes continue_task(*task), |
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Lock gang monitor |
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Check that task is the same as current binding |
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If not, abort with an error |
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Else, set the number of active workers as requested? |
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Notify workers that they can continue from yield points |
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New workers can also start up as required |
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while satisfying the constraint that |
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active + yielded does not exceed required number |
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Wait (as above). |
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NOTE: In the above, for simplicity in a first iteration |
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our gangs will be of fixed population and will not |
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therefore be flexible work gangs, just yielding work |
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gangs. Once this works well, we will in a second |
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iteration.refinement introduce flexibility into |
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the work gang. |
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NOTE: we can always create a new gang per each iteration |
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in order to get the flexibility, but we will for now |
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desist that simplified route. |
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*/ |
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///////////////////// |
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void YieldingFlexibleWorkGang::start_task(YieldingFlexibleGangTask* new_task) { |
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MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
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assert(task() == NULL, "Gang currently tied to a task"); |
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assert(new_task != NULL, "Null task"); |
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// Bind task to gang |
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_task = new_task; |
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new_task->set_gang(this); // Establish 2-way binding to support yielding |
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_sequence_number++; |
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uint requested_size = new_task->requested_size(); |
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assert(requested_size >= 0, "Should be non-negative"); |
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if (requested_size != 0) { |
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_active_workers = MIN2(requested_size, total_workers()); |
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} else { |
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_active_workers = active_workers(); |
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} |
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new_task->set_actual_size(_active_workers); |
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new_task->set_for_termination(_active_workers); |
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assert(_started_workers == 0, "Tabula rasa non"); |
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assert(_finished_workers == 0, "Tabula rasa non"); |
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assert(_yielded_workers == 0, "Tabula rasa non"); |
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yielding_task()->set_status(ACTIVE); |
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// Wake up all the workers, the first few will get to work, |
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// and the rest will go back to sleep |
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monitor()->notify_all(); |
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wait_for_gang(); |
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} |
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void YieldingFlexibleWorkGang::wait_for_gang() { |
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assert(monitor()->owned_by_self(), "Data race"); |
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// Wait for task to complete or yield |
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for (Status status = yielding_task()->status(); |
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status != COMPLETED && status != YIELDED && status != ABORTED; |
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status = yielding_task()->status()) { |
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assert(started_workers() <= active_workers(), "invariant"); |
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assert(finished_workers() <= active_workers(), "invariant"); |
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assert(yielded_workers() <= active_workers(), "invariant"); |
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monitor()->wait(Mutex::_no_safepoint_check_flag); |
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} |
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switch (yielding_task()->status()) { |
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case COMPLETED: |
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case ABORTED: { |
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assert(finished_workers() == active_workers(), "Inconsistent status"); |
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assert(yielded_workers() == 0, "Invariant"); |
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reset(); // for next task; gang<->task binding released |
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break; |
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} |
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case YIELDED: { |
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assert(yielded_workers() > 0, "Invariant"); |
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assert(yielded_workers() + finished_workers() == active_workers(), |
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"Inconsistent counts"); |
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break; |
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} |
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case ACTIVE: |
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case INACTIVE: |
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case COMPLETING: |
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case YIELDING: |
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case ABORTING: |
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default: |
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ShouldNotReachHere(); |
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} |
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} |
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void YieldingFlexibleWorkGang::continue_task( |
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YieldingFlexibleGangTask* gang_task) { |
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MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
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assert(task() != NULL && task() == gang_task, "Incorrect usage"); |
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assert(_started_workers == _active_workers, "Precondition"); |
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assert(_yielded_workers > 0 && yielding_task()->status() == YIELDED, |
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"Else why are we calling continue_task()"); |
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// Restart the yielded gang workers |
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yielding_task()->set_status(ACTIVE); |
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monitor()->notify_all(); |
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wait_for_gang(); |
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} |
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void YieldingFlexibleWorkGang::reset() { |
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_started_workers = 0; |
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_finished_workers = 0; |
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yielding_task()->set_gang(NULL); |
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_task = NULL; // unbind gang from task |
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} |
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void YieldingFlexibleWorkGang::yield() { |
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assert(task() != NULL, "Inconsistency; should have task binding"); |
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MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
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assert(yielded_workers() < active_workers(), "Consistency check"); |
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if (yielding_task()->status() == ABORTING) { |
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// Do not yield; we need to abort as soon as possible |
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// XXX NOTE: This can cause a performance pathology in the |
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// current implementation in Mustang, as of today, and |
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// pre-Mustang in that as soon as an overflow occurs, |
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// yields will not be honoured. The right way to proceed |
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// of course is to fix bug # TBF, so that abort's cause |
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// us to return at each potential yield point. |
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return; |
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} |
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if (++_yielded_workers + finished_workers() == active_workers()) { |
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yielding_task()->set_status(YIELDED); |
216 |
monitor()->notify_all(); |
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} else { |
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yielding_task()->set_status(YIELDING); |
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} |
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||
221 |
while (true) { |
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switch (yielding_task()->status()) { |
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case YIELDING: |
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case YIELDED: { |
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monitor()->wait(Mutex::_no_safepoint_check_flag); |
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break; // from switch |
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} |
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case ACTIVE: |
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case ABORTING: |
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case COMPLETING: { |
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assert(_yielded_workers > 0, "Else why am i here?"); |
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_yielded_workers--; |
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return; |
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} |
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case INACTIVE: |
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236 |
case ABORTED: |
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237 |
case COMPLETED: |
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238 |
default: { |
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ShouldNotReachHere(); |
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240 |
} |
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} |
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} |
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// Only return is from inside switch statement above |
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ShouldNotReachHere(); |
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} |
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||
247 |
void YieldingFlexibleWorkGang::abort() { |
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248 |
assert(task() != NULL, "Inconsistency; should have task binding"); |
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249 |
MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag); |
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250 |
assert(yielded_workers() < active_workers(), "Consistency check"); |
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#ifndef PRODUCT |
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252 |
switch (yielding_task()->status()) { |
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253 |
// allowed states |
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254 |
case ACTIVE: |
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255 |
case ABORTING: |
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256 |
case COMPLETING: |
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257 |
case YIELDING: |
|
258 |
break; |
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259 |
// not allowed states |
|
260 |
case INACTIVE: |
|
261 |
case ABORTED: |
|
262 |
case COMPLETED: |
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263 |
case YIELDED: |
|
264 |
default: |
|
265 |
ShouldNotReachHere(); |
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266 |
} |
|
267 |
#endif // !PRODUCT |
|
268 |
Status prev_status = yielding_task()->status(); |
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269 |
yielding_task()->set_status(ABORTING); |
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270 |
if (prev_status == YIELDING) { |
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271 |
assert(yielded_workers() > 0, "Inconsistency"); |
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272 |
// At least one thread has yielded, wake it up |
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273 |
// so it can go back to waiting stations ASAP. |
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274 |
monitor()->notify_all(); |
|
275 |
} |
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276 |
} |
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277 |
||
278 |
/////////////////////////////// |
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279 |
// YieldingFlexibleGangTask |
|
280 |
/////////////////////////////// |
|
281 |
void YieldingFlexibleGangTask::yield() { |
|
282 |
assert(gang() != NULL, "No gang to signal"); |
|
283 |
gang()->yield(); |
|
284 |
} |
|
285 |
||
286 |
void YieldingFlexibleGangTask::abort() { |
|
287 |
assert(gang() != NULL, "No gang to signal"); |
|
288 |
gang()->abort(); |
|
289 |
} |
|
290 |
||
291 |
/////////////////////////////// |
|
292 |
// YieldingFlexibleGangWorker |
|
293 |
/////////////////////////////// |
|
294 |
void YieldingFlexibleGangWorker::loop() { |
|
295 |
int previous_sequence_number = 0; |
|
296 |
Monitor* gang_monitor = gang()->monitor(); |
|
297 |
MutexLockerEx ml(gang_monitor, Mutex::_no_safepoint_check_flag); |
|
298 |
WorkData data; |
|
299 |
int id; |
|
300 |
while (true) { |
|
301 |
// Check if there is work to do or if we have been asked |
|
302 |
// to terminate |
|
303 |
gang()->internal_worker_poll(&data); |
|
304 |
if (data.terminate()) { |
|
305 |
// We have been asked to terminate. |
|
306 |
assert(gang()->task() == NULL, "No task binding"); |
|
307 |
// set_status(TERMINATED); |
|
308 |
return; |
|
309 |
} else if (data.task() != NULL && |
|
310 |
data.sequence_number() != previous_sequence_number) { |
|
311 |
// There is work to be done. |
|
312 |
// First check if we need to become active or if there |
|
313 |
// are already the requisite number of workers |
|
314 |
if (gang()->started_workers() == yf_gang()->active_workers()) { |
|
315 |
// There are already enough workers, we do not need to |
|
316 |
// to run; fall through and wait on monitor. |
|
317 |
} else { |
|
318 |
// We need to pitch in and do the work. |
|
319 |
assert(gang()->started_workers() < yf_gang()->active_workers(), |
|
320 |
"Unexpected state"); |
|
321 |
id = gang()->started_workers(); |
|
322 |
gang()->internal_note_start(); |
|
323 |
// Now, release the gang mutex and do the work. |
|
324 |
{ |
|
325 |
MutexUnlockerEx mul(gang_monitor, Mutex::_no_safepoint_check_flag); |
|
326 |
data.task()->work(id); // This might include yielding |
|
327 |
} |
|
328 |
// Reacquire monitor and note completion of this worker |
|
329 |
gang()->internal_note_finish(); |
|
330 |
// Update status of task based on whether all workers have |
|
331 |
// finished or some have yielded |
|
332 |
assert(data.task() == gang()->task(), "Confused task binding"); |
|
333 |
if (gang()->finished_workers() == yf_gang()->active_workers()) { |
|
334 |
switch (data.yf_task()->status()) { |
|
335 |
case ABORTING: { |
|
336 |
data.yf_task()->set_status(ABORTED); |
|
337 |
break; |
|
338 |
} |
|
339 |
case ACTIVE: |
|
340 |
case COMPLETING: { |
|
341 |
data.yf_task()->set_status(COMPLETED); |
|
342 |
break; |
|
343 |
} |
|
344 |
default: |
|
345 |
ShouldNotReachHere(); |
|
346 |
} |
|
347 |
gang_monitor->notify_all(); // Notify overseer |
|
348 |
} else { // at least one worker is still working or yielded |
|
349 |
assert(gang()->finished_workers() < yf_gang()->active_workers(), |
|
350 |
"Counts inconsistent"); |
|
351 |
switch (data.yf_task()->status()) { |
|
352 |
case ACTIVE: { |
|
353 |
// first, but not only thread to complete |
|
354 |
data.yf_task()->set_status(COMPLETING); |
|
355 |
break; |
|
356 |
} |
|
357 |
case YIELDING: { |
|
358 |
if (gang()->finished_workers() + yf_gang()->yielded_workers() |
|
359 |
== yf_gang()->active_workers()) { |
|
360 |
data.yf_task()->set_status(YIELDED); |
|
361 |
gang_monitor->notify_all(); // notify overseer |
|
362 |
} |
|
363 |
break; |
|
364 |
} |
|
365 |
case ABORTING: |
|
366 |
case COMPLETING: { |
|
367 |
break; // nothing to do |
|
368 |
} |
|
369 |
default: // everything else: INACTIVE, YIELDED, ABORTED, COMPLETED |
|
370 |
ShouldNotReachHere(); |
|
371 |
} |
|
372 |
} |
|
373 |
} |
|
374 |
} |
|
375 |
// Remember the sequence number |
|
376 |
previous_sequence_number = data.sequence_number(); |
|
377 |
// Wait for more work |
|
378 |
gang_monitor->wait(Mutex::_no_safepoint_check_flag); |
|
379 |
} |
|
380 |
} |