aoqi@0: /*
aoqi@0:  * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  *
aoqi@0:  */
aoqi@0: 
aoqi@0: #include "precompiled.hpp"
aoqi@0: #include "memory/gcLocker.inline.hpp"
aoqi@0: #include "memory/resourceArea.hpp"
aoqi@0: #include "memory/sharedHeap.hpp"
aoqi@0: 
aoqi@0: volatile jint GC_locker::_jni_lock_count = 0;
aoqi@0: volatile bool GC_locker::_needs_gc       = false;
aoqi@0: volatile bool GC_locker::_doing_gc       = false;
aoqi@0: 
aoqi@0: #ifdef ASSERT
aoqi@0: volatile jint GC_locker::_debug_jni_lock_count = 0;
aoqi@0: #endif
aoqi@0: 
aoqi@0: 
aoqi@0: #ifdef ASSERT
aoqi@0: void GC_locker::verify_critical_count() {
aoqi@0:   if (SafepointSynchronize::is_at_safepoint()) {
aoqi@0:     assert(!needs_gc() || _debug_jni_lock_count == _jni_lock_count, "must agree");
aoqi@0:     int count = 0;
aoqi@0:     // Count the number of threads with critical operations in progress
aoqi@0:     for (JavaThread* thr = Threads::first(); thr; thr = thr->next()) {
aoqi@0:       if (thr->in_critical()) {
aoqi@0:         count++;
aoqi@0:       }
aoqi@0:     }
aoqi@0:     if (_jni_lock_count != count) {
aoqi@0:       tty->print_cr("critical counts don't match: %d != %d", _jni_lock_count, count);
aoqi@0:       for (JavaThread* thr = Threads::first(); thr; thr = thr->next()) {
aoqi@0:         if (thr->in_critical()) {
aoqi@0:           tty->print_cr(INTPTR_FORMAT " in_critical %d", p2i(thr), thr->in_critical());
aoqi@0:         }
aoqi@0:       }
aoqi@0:     }
aoqi@0:     assert(_jni_lock_count == count, "must be equal");
aoqi@0:   }
aoqi@0: }
aoqi@0: #endif
aoqi@0: 
aoqi@0: bool GC_locker::check_active_before_gc() {
aoqi@0:   assert(SafepointSynchronize::is_at_safepoint(), "only read at safepoint");
aoqi@0:   if (is_active() && !_needs_gc) {
aoqi@0:     verify_critical_count();
aoqi@0:     _needs_gc = true;
aoqi@0:     if (PrintJNIGCStalls && PrintGCDetails) {
aoqi@0:       ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
aoqi@0:       gclog_or_tty->print_cr("%.3f: Setting _needs_gc. Thread \"%s\" %d locked.",
aoqi@0:                              gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
aoqi@0:     }
aoqi@0: 
aoqi@0:   }
aoqi@0:   return is_active();
aoqi@0: }
aoqi@0: 
aoqi@0: void GC_locker::stall_until_clear() {
aoqi@0:   assert(!JavaThread::current()->in_critical(), "Would deadlock");
aoqi@0:   MutexLocker   ml(JNICritical_lock);
aoqi@0: 
aoqi@0:   if (needs_gc()) {
aoqi@0:     if (PrintJNIGCStalls && PrintGCDetails) {
aoqi@0:       ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
aoqi@0:       gclog_or_tty->print_cr("%.3f: Allocation failed. Thread \"%s\" is stalled by JNI critical section, %d locked.",
aoqi@0:                              gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
aoqi@0:     }
aoqi@0:   }
aoqi@0: 
aoqi@0:   // Wait for _needs_gc  to be cleared
aoqi@0:   while (needs_gc()) {
aoqi@0:     JNICritical_lock->wait();
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: void GC_locker::jni_lock(JavaThread* thread) {
aoqi@0:   assert(!thread->in_critical(), "shouldn't currently be in a critical region");
aoqi@0:   MutexLocker mu(JNICritical_lock);
aoqi@0:   // Block entering threads if we know at least one thread is in a
aoqi@0:   // JNI critical region and we need a GC.
aoqi@0:   // We check that at least one thread is in a critical region before
aoqi@0:   // blocking because blocked threads are woken up by a thread exiting
aoqi@0:   // a JNI critical region.
aoqi@0:   while (is_active_and_needs_gc() || _doing_gc) {
aoqi@0:     JNICritical_lock->wait();
aoqi@0:   }
aoqi@0:   thread->enter_critical();
aoqi@0:   _jni_lock_count++;
aoqi@0:   increment_debug_jni_lock_count();
aoqi@0: }
aoqi@0: 
aoqi@0: void GC_locker::jni_unlock(JavaThread* thread) {
aoqi@0:   assert(thread->in_last_critical(), "should be exiting critical region");
aoqi@0:   MutexLocker mu(JNICritical_lock);
aoqi@0:   _jni_lock_count--;
aoqi@0:   decrement_debug_jni_lock_count();
aoqi@0:   thread->exit_critical();
aoqi@0:   if (needs_gc() && !is_active_internal()) {
aoqi@0:     // We're the last thread out. Cause a GC to occur.
aoqi@0:     _doing_gc = true;
aoqi@0:     {
aoqi@0:       // Must give up the lock while at a safepoint
aoqi@0:       MutexUnlocker munlock(JNICritical_lock);
aoqi@0:       if (PrintJNIGCStalls && PrintGCDetails) {
aoqi@0:         ResourceMark rm; // JavaThread::name() allocates to convert to UTF8
aoqi@0:         gclog_or_tty->print_cr("%.3f: Thread \"%s\" is performing GC after exiting critical section, %d locked",
aoqi@0:             gclog_or_tty->time_stamp().seconds(), Thread::current()->name(), _jni_lock_count);
aoqi@0:       }
aoqi@0:       Universe::heap()->collect(GCCause::_gc_locker);
aoqi@0:     }
aoqi@0:     _doing_gc = false;
aoqi@0:     _needs_gc = false;
aoqi@0:     JNICritical_lock->notify_all();
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: // Implementation of No_GC_Verifier
aoqi@0: 
aoqi@0: #ifdef ASSERT
aoqi@0: 
aoqi@0: No_GC_Verifier::No_GC_Verifier(bool verifygc) {
aoqi@0:   _verifygc = verifygc;
aoqi@0:   if (_verifygc) {
aoqi@0:     CollectedHeap* h = Universe::heap();
aoqi@0:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
aoqi@0:     _old_invocations = h->total_collections();
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: No_GC_Verifier::~No_GC_Verifier() {
aoqi@0:   if (_verifygc) {
aoqi@0:     CollectedHeap* h = Universe::heap();
aoqi@0:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
aoqi@0:     if (_old_invocations != h->total_collections()) {
aoqi@0:       fatal("collection in a No_GC_Verifier secured function");
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: Pause_No_GC_Verifier::Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {
aoqi@0:   _ngcv = ngcv;
aoqi@0:   if (_ngcv->_verifygc) {
aoqi@0:     // if we were verifying, then make sure that nothing is
aoqi@0:     // wrong before we "pause" verification
aoqi@0:     CollectedHeap* h = Universe::heap();
aoqi@0:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
aoqi@0:     if (_ngcv->_old_invocations != h->total_collections()) {
aoqi@0:       fatal("collection in a No_GC_Verifier secured function");
aoqi@0:     }
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: Pause_No_GC_Verifier::~Pause_No_GC_Verifier() {
aoqi@0:   if (_ngcv->_verifygc) {
aoqi@0:     // if we were verifying before, then reenable verification
aoqi@0:     CollectedHeap* h = Universe::heap();
aoqi@0:     assert(!h->is_gc_active(), "GC active during No_GC_Verifier");
aoqi@0:     _ngcv->_old_invocations = h->total_collections();
aoqi@0:   }
aoqi@0: }
aoqi@0: 
aoqi@0: 
aoqi@0: // JRT_LEAF rules:
aoqi@0: // A JRT_LEAF method may not interfere with safepointing by
aoqi@0: //   1) acquiring or blocking on a Mutex or JavaLock - checked
aoqi@0: //   2) allocating heap memory - checked
aoqi@0: //   3) executing a VM operation - checked
aoqi@0: //   4) executing a system call (including malloc) that could block or grab a lock
aoqi@0: //   5) invoking GC
aoqi@0: //   6) reaching a safepoint
aoqi@0: //   7) running too long
aoqi@0: // Nor may any method it calls.
aoqi@0: JRT_Leaf_Verifier::JRT_Leaf_Verifier()
aoqi@0:   : No_Safepoint_Verifier(true, JRT_Leaf_Verifier::should_verify_GC())
aoqi@0: {
aoqi@0: }
aoqi@0: 
aoqi@0: JRT_Leaf_Verifier::~JRT_Leaf_Verifier()
aoqi@0: {
aoqi@0: }
aoqi@0: 
aoqi@0: bool JRT_Leaf_Verifier::should_verify_GC() {
aoqi@0:   switch (JavaThread::current()->thread_state()) {
aoqi@0:   case _thread_in_Java:
aoqi@0:     // is in a leaf routine, there must be no safepoint.
aoqi@0:     return true;
aoqi@0:   case _thread_in_native:
aoqi@0:     // A native thread is not subject to safepoints.
aoqi@0:     // Even while it is in a leaf routine, GC is ok
aoqi@0:     return false;
aoqi@0:   default:
aoqi@0:     // Leaf routines cannot be called from other contexts.
aoqi@0:     ShouldNotReachHere();
aoqi@0:     return false;
aoqi@0:   }
aoqi@0: }
aoqi@0: #endif