| /* |
| * Copyright (c) 2018, Red Hat, Inc. All rights reserved. |
| * |
| * 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 "gc/shenandoah/shenandoahHeap.inline.hpp" |
| #include "gc/shenandoah/shenandoahUtils.hpp" |
| #include "gc/shenandoah/shenandoahEvacOOMHandler.hpp" |
| #include "gc/shenandoah/shenandoahThreadLocalData.hpp" |
| #include "runtime/orderAccess.hpp" |
| #include "runtime/os.hpp" |
| #include "runtime/thread.hpp" |
| |
| const jint ShenandoahEvacOOMHandler::OOM_MARKER_MASK = 0x80000000; |
| |
| ShenandoahEvacOOMHandler::ShenandoahEvacOOMHandler() : |
| _threads_in_evac(0) { |
| } |
| |
| void ShenandoahEvacOOMHandler::wait_for_no_evac_threads() { |
| while ((OrderAccess::load_acquire(&_threads_in_evac) & ~OOM_MARKER_MASK) != 0) { |
| os::naked_short_sleep(1); |
| } |
| // At this point we are sure that no threads can evacuate anything. Raise |
| // the thread-local oom_during_evac flag to indicate that any attempt |
| // to evacuate should simply return the forwarding pointer instead (which is safe now). |
| ShenandoahThreadLocalData::set_oom_during_evac(Thread::current(), true); |
| } |
| |
| void ShenandoahEvacOOMHandler::enter_evacuation() { |
| jint threads_in_evac = OrderAccess::load_acquire(&_threads_in_evac); |
| |
| assert(!ShenandoahThreadLocalData::is_evac_allowed(Thread::current()), "sanity"); |
| assert(!ShenandoahThreadLocalData::is_oom_during_evac(Thread::current()), "TL oom-during-evac must not be set"); |
| |
| if ((threads_in_evac & OOM_MARKER_MASK) != 0) { |
| wait_for_no_evac_threads(); |
| return; |
| } |
| |
| while (true) { |
| jint other = Atomic::cmpxchg(threads_in_evac + 1, &_threads_in_evac, threads_in_evac); |
| if (other == threads_in_evac) { |
| // Success: caller may safely enter evacuation |
| DEBUG_ONLY(ShenandoahThreadLocalData::set_evac_allowed(Thread::current(), true)); |
| return; |
| } else { |
| // Failure: |
| // - if offender has OOM_MARKER_MASK, then loop until no more threads in evac |
| // - otherwise re-try CAS |
| if ((other & OOM_MARKER_MASK) != 0) { |
| wait_for_no_evac_threads(); |
| return; |
| } |
| threads_in_evac = other; |
| } |
| } |
| } |
| |
| void ShenandoahEvacOOMHandler::leave_evacuation() { |
| if (!ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) { |
| assert((OrderAccess::load_acquire(&_threads_in_evac) & ~OOM_MARKER_MASK) > 0, "sanity"); |
| // NOTE: It's ok to simply decrement, even with mask set, because unmasked value is positive. |
| Atomic::dec(&_threads_in_evac); |
| } else { |
| // If we get here, the current thread has already gone through the |
| // OOM-during-evac protocol and has thus either never entered or successfully left |
| // the evacuation region. Simply flip its TL oom-during-evac flag back off. |
| ShenandoahThreadLocalData::set_oom_during_evac(Thread::current(), false); |
| } |
| DEBUG_ONLY(ShenandoahThreadLocalData::set_evac_allowed(Thread::current(), false)); |
| assert(!ShenandoahThreadLocalData::is_oom_during_evac(Thread::current()), "TL oom-during-evac must be turned off"); |
| } |
| |
| void ShenandoahEvacOOMHandler::handle_out_of_memory_during_evacuation() { |
| assert(ShenandoahThreadLocalData::is_evac_allowed(Thread::current()), "sanity"); |
| assert(!ShenandoahThreadLocalData::is_oom_during_evac(Thread::current()), "TL oom-during-evac must not be set"); |
| |
| jint threads_in_evac = OrderAccess::load_acquire(&_threads_in_evac); |
| while (true) { |
| jint other = Atomic::cmpxchg((threads_in_evac - 1) | OOM_MARKER_MASK, |
| &_threads_in_evac, threads_in_evac); |
| if (other == threads_in_evac) { |
| // Success: wait for other threads to get out of the protocol and return. |
| wait_for_no_evac_threads(); |
| return; |
| } else { |
| // Failure: try again with updated new value. |
| threads_in_evac = other; |
| } |
| } |
| } |
| |
| void ShenandoahEvacOOMHandler::clear() { |
| assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "must be at a safepoint"); |
| assert((OrderAccess::load_acquire(&_threads_in_evac) & ~OOM_MARKER_MASK) == 0, "sanity"); |
| OrderAccess::release_store_fence<jint>(&_threads_in_evac, 0); |
| } |
| |
| ShenandoahEvacOOMScope::ShenandoahEvacOOMScope() { |
| ShenandoahHeap::heap()->enter_evacuation(); |
| } |
| |
| ShenandoahEvacOOMScope::~ShenandoahEvacOOMScope() { |
| ShenandoahHeap::heap()->leave_evacuation(); |
| } |