duke@435: /*
never@3494:  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #include "precompiled.hpp"
stefank@2314: #include "memory/gcLocker.inline.hpp"
stefank@2314: #include "memory/resourceArea.hpp"
stefank@2314: #include "memory/sharedHeap.hpp"
duke@435: 
duke@435: volatile jint GC_locker::_jni_lock_count = 0;
duke@435: volatile jint GC_locker::_lock_count     = 0;
duke@435: volatile bool GC_locker::_needs_gc       = false;
duke@435: volatile bool GC_locker::_doing_gc       = false;
never@3494: 
never@3494: #ifdef ASSERT
never@3494: volatile jint GC_locker::_debug_jni_lock_count = 0;
never@3494: #endif
never@3494: 
never@3494: 
never@3494: #ifdef ASSERT
never@3494: void GC_locker::verify_critical_count() {
never@3494:   if (SafepointSynchronize::is_at_safepoint()) {
never@3494:     assert(!needs_gc() || _debug_jni_lock_count == _jni_lock_count, "must agree");
never@3494:     int count = 0;
never@3494:     // Count the number of threads with critical operations in progress
never@3494:     for (JavaThread* thr = Threads::first(); thr; thr = thr->next()) {
never@3494:       if (thr->in_critical()) {
never@3494:         count++;
never@3494:       }
never@3494:     }
never@3494:     if (_jni_lock_count != count) {
never@3494:       tty->print_cr("critical counts don't match: %d != %d", _jni_lock_count, count);
never@3494:       for (JavaThread* thr = Threads::first(); thr; thr = thr->next()) {
never@3494:         if (thr->in_critical()) {
never@3494:           tty->print_cr(INTPTR_FORMAT " in_critical %d", thr, thr->in_critical());
never@3494:         }
never@3494:       }
never@3494:     }
never@3494:     assert(_jni_lock_count == count, "must be equal");
never@3494:   }
never@3494: }
never@3494: #endif
never@3494: 
never@3494: bool GC_locker::check_active_before_gc() {
never@3494:   assert(SafepointSynchronize::is_at_safepoint(), "only read at safepoint");
never@3494:   if (is_active() && !_needs_gc) {
never@3494:     verify_critical_count();
never@3494:     _needs_gc = true;
never@3494:     if (PrintJNIGCStalls && PrintGCDetails) {
never@3494:       ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
never@3571:       gclog_or_tty->print_cr("%.3f: Setting _needs_gc. Thread \"%s\" %d locked.",
never@3571:                              gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
never@3494:     }
never@3494: 
never@3494:   }
never@3494:   return is_active();
never@3494: }
duke@435: 
duke@435: void GC_locker::stall_until_clear() {
duke@435:   assert(!JavaThread::current()->in_critical(), "Would deadlock");
never@3494:   MutexLocker   ml(JNICritical_lock);
never@3494: 
never@3494:   if (needs_gc()) {
never@3494:     if (PrintJNIGCStalls && PrintGCDetails) {
never@3494:       ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
never@3571:       gclog_or_tty->print_cr("%.3f: Allocation failed. Thread \"%s\" is stalled by JNI critical section, %d locked.",
never@3571:                              gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
never@3494:     }
apetrusenko@574:   }
never@3494: 
duke@435:   // Wait for _needs_gc  to be cleared
never@3494:   while (needs_gc()) {
duke@435:     JNICritical_lock->wait();
duke@435:   }
duke@435: }
duke@435: 
never@3494: void GC_locker::jni_lock(JavaThread* thread) {
never@3494:   assert(!thread->in_critical(), "shouldn't currently be in a critical region");
duke@435:   MutexLocker mu(JNICritical_lock);
duke@435:   // Block entering threads if we know at least one thread is in a
duke@435:   // JNI critical region and we need a GC.
duke@435:   // We check that at least one thread is in a critical region before
duke@435:   // blocking because blocked threads are woken up by a thread exiting
duke@435:   // a JNI critical region.
never@3494:   while ((needs_gc() && is_jni_active()) || _doing_gc) {
duke@435:     JNICritical_lock->wait();
duke@435:   }
never@3494:   thread->enter_critical();
never@3494:   _jni_lock_count++;
never@3494:   increment_debug_jni_lock_count();
duke@435: }
duke@435: 
never@3494: void GC_locker::jni_unlock(JavaThread* thread) {
never@3494:   assert(thread->in_last_critical(), "should be exiting critical region");
duke@435:   MutexLocker mu(JNICritical_lock);
never@3494:   _jni_lock_count--;
never@3494:   decrement_debug_jni_lock_count();
never@3494:   thread->exit_critical();
duke@435:   if (needs_gc() && !is_jni_active()) {
duke@435:     // We're the last thread out. Cause a GC to occur.
duke@435:     // GC will also check is_active, so this check is not
duke@435:     // strictly needed. It's added here to make it clear that
duke@435:     // the GC will NOT be performed if any other caller
duke@435:     // of GC_locker::lock() still needs GC locked.
stefank@5769:     if (!is_active_internal()) {
duke@435:       _doing_gc = true;
duke@435:       {
duke@435:         // Must give up the lock while at a safepoint
duke@435:         MutexUnlocker munlock(JNICritical_lock);
never@3494:         if (PrintJNIGCStalls && PrintGCDetails) {
never@3494:           ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
never@3571:           gclog_or_tty->print_cr("%.3f: Thread \"%s\" is performing GC after exiting critical section, %d locked",
never@3571:                                  gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
never@3494:         }
duke@435:         Universe::heap()->collect(GCCause::_gc_locker);
duke@435:       }
duke@435:       _doing_gc = false;
duke@435:     }
never@3494: 
never@3494:     _needs_gc = false;
duke@435:     JNICritical_lock->notify_all();
duke@435:   }
duke@435: }
duke@435: 
duke@435: // Implementation of No_GC_Verifier
duke@435: 
duke@435: #ifdef ASSERT
duke@435: 
duke@435: No_GC_Verifier::No_GC_Verifier(bool verifygc) {
duke@435:   _verifygc = verifygc;
duke@435:   if (_verifygc) {
duke@435:     CollectedHeap* h = Universe::heap();
duke@435:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
duke@435:     _old_invocations = h->total_collections();
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: No_GC_Verifier::~No_GC_Verifier() {
duke@435:   if (_verifygc) {
duke@435:     CollectedHeap* h = Universe::heap();
duke@435:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
duke@435:     if (_old_invocations != h->total_collections()) {
duke@435:       fatal("collection in a No_GC_Verifier secured function");
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {
duke@435:   _ngcv = ngcv;
duke@435:   if (_ngcv->_verifygc) {
duke@435:     // if we were verifying, then make sure that nothing is
duke@435:     // wrong before we "pause" verification
duke@435:     CollectedHeap* h = Universe::heap();
duke@435:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
duke@435:     if (_ngcv->_old_invocations != h->total_collections()) {
duke@435:       fatal("collection in a No_GC_Verifier secured function");
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: Pause_No_GC_Verifier::~Pause_No_GC_Verifier() {
duke@435:   if (_ngcv->_verifygc) {
duke@435:     // if we were verifying before, then reenable verification
duke@435:     CollectedHeap* h = Universe::heap();
duke@435:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
duke@435:     _ngcv->_old_invocations = h->total_collections();
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: // JRT_LEAF rules:
duke@435: // A JRT_LEAF method may not interfere with safepointing by
duke@435: //   1) acquiring or blocking on a Mutex or JavaLock - checked
duke@435: //   2) allocating heap memory - checked
duke@435: //   3) executing a VM operation - checked
duke@435: //   4) executing a system call (including malloc) that could block or grab a lock
duke@435: //   5) invoking GC
duke@435: //   6) reaching a safepoint
duke@435: //   7) running too long
duke@435: // Nor may any method it calls.
duke@435: JRT_Leaf_Verifier::JRT_Leaf_Verifier()
duke@435:   : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC())
duke@435: {
duke@435: }
duke@435: 
duke@435: JRT_Leaf_Verifier::~JRT_Leaf_Verifier()
duke@435: {
duke@435: }
duke@435: 
duke@435: bool JRT_Leaf_Verifier::should_verify_GC() {
duke@435:   switch (JavaThread::current()->thread_state()) {
duke@435:   case _thread_in_Java:
duke@435:     // is in a leaf routine, there must be no safepoint.
duke@435:     return true;
duke@435:   case _thread_in_native:
duke@435:     // A native thread is not subject to safepoints.
duke@435:     // Even while it is in a leaf routine, GC is ok
duke@435:     return false;
duke@435:   default:
duke@435:     // Leaf routines cannot be called from other contexts.
duke@435:     ShouldNotReachHere();
duke@435:     return false;
duke@435:   }
duke@435: }
duke@435: #endif