graal-jvmci-8: src/share/vm/memory/gcLocker.hpp comparison

comparison src/share/vm/memory/gcLocker.hpp @ 0:a61af66fc99e jdk7-b24

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author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
parents
children	deb97b8ef02b

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--1:000000000000
+:a61af66fc99e
+/*
+* Copyright 1997-2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+* CA 95054 USA or visit www.sun.com if you need additional information or
+* have any questions.
+*
+*/
+// The direct lock/unlock calls do not force a collection if an unlock
+// decrements the count to zero. Avoid calling these if at all possible.
+class GC_locker: public AllStatic {
+private:
+static volatile jint _jni_lock_count;  // number of jni active instances
+static volatile jint _lock_count;      // number of other active instances
+static volatile bool _needs_gc;        // heap is filling, we need a GC
+// note: bool is typedef'd as jint
+static volatile bool _doing_gc;        // unlock_critical() is doing a GC
+// Accessors
+static bool is_jni_active() {
+return _jni_lock_count > 0;
+}
+static void set_needs_gc() {
+assert(SafepointSynchronize::is_at_safepoint(),
+"needs_gc is only set at a safepoint");
+_needs_gc = true;
+}
+static void clear_needs_gc() {
+assert_lock_strong(JNICritical_lock);
+_needs_gc = false;
+}
+static void jni_lock() {
+Atomic::inc(&_jni_lock_count);
+CHECK_UNHANDLED_OOPS_ONLY(
+if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count++; })
+assert(Universe::heap() == NULL || !Universe::heap()->is_gc_active(),
+"locking failed");
+}
+static void jni_unlock() {
+Atomic::dec(&_jni_lock_count);
+CHECK_UNHANDLED_OOPS_ONLY(
+if (CheckUnhandledOops) { Thread::current()->_gc_locked_out_count--; })
+}
+static void jni_lock_slow();
+static void jni_unlock_slow();
+public:
+// Accessors
+static bool is_active();
+static bool needs_gc()       { return _needs_gc;                        }
+// Shorthand
+static bool is_active_and_needs_gc() { return is_active() && needs_gc();}
+// Calls set_needs_gc() if is_active() is true. Returns is_active().
+static bool check_active_before_gc();
+// Stalls the caller (who should not be in a jni critical section)
+// until needs_gc() clears. Note however that needs_gc() may be
+// set at a subsequent safepoint and/or cleared under the
+// JNICritical_lock, so the caller may not safely assert upon
+// return from this method that "!needs_gc()" since that is
+// not a stable predicate.
+static void stall_until_clear();
+// Non-structured GC locking: currently needed for JNI. Use with care!
+static void lock();
+static void unlock();
+// The following two methods are used for JNI critical regions.
+// If we find that we failed to perform a GC because the GC_locker
+// was active, arrange for one as soon as possible by allowing
+// all threads in critical regions to complete, but not allowing
+// other critical regions to be entered. The reasons for that are:
+// 1) a GC request won't be starved by overlapping JNI critical
+//    region activities, which can cause unnecessary OutOfMemory errors.
+// 2) even if allocation requests can still be satisfied before GC locker
+//    becomes inactive, for example, in tenured generation possibly with
+//    heap expansion, those allocations can trigger lots of safepointing
+//    attempts (ineffective GC attempts) and require Heap_lock which
+//    slow down allocations tremendously.
+//
+// Note that critical regions can be nested in a single thread, so
+// we must allow threads already in critical regions to continue.
+//
+// JNI critical regions are the only participants in this scheme
+// because they are, by spec, well bounded while in a critical region.
+//
+// Each of the following two method is split into a fast path and a slow
+// path. JNICritical_lock is only grabbed in the slow path.
+// _needs_gc is initially false and every java thread will go
+// through the fast path (which does the same thing as the slow path
+// when _needs_gc is false). When GC happens at a safepoint,
+// GC_locker::is_active() is checked. Since there is no safepoint in the
+// fast path of lock_critical() and unlock_critical(), there is no race
+// condition between the fast path and GC. After _needs_gc is set at a
+// safepoint, every thread will go through the slow path after the safepoint.
+// Since after a safepoint, each of the following two methods is either
+// entered from the method entry and falls into the slow path, or is
+// resumed from the safepoints in the method, which only exist in the slow
+// path. So when _needs_gc is set, the slow path is always taken, till
+// _needs_gc is cleared.
+static void lock_critical(JavaThread* thread);
+static void unlock_critical(JavaThread* thread);
+};
+// A No_GC_Verifier object can be placed in methods where one assumes that
+// no garbage collection will occur. The destructor will verify this property
+// unless the constructor is called with argument false (not verifygc).
+//
+// The check will only be done in debug mode and if verifygc true.
+class No_GC_Verifier: public StackObj {
+friend class Pause_No_GC_Verifier;
+protected:
+bool _verifygc;
+unsigned int _old_invocations;
+public:
+#ifdef ASSERT
+No_GC_Verifier(bool verifygc = true);
+~No_GC_Verifier();
+#else
+No_GC_Verifier(bool verifygc = true) {}
+~No_GC_Verifier() {}
+#endif
+};
+// A Pause_No_GC_Verifier is used to temporarily pause the behavior
+// of a No_GC_Verifier object. If we are not in debug mode or if the
+// No_GC_Verifier object has a _verifygc value of false, then there
+// is nothing to do.
+class Pause_No_GC_Verifier: public StackObj {
+private:
+No_GC_Verifier * _ngcv;
+public:
+#ifdef ASSERT
+Pause_No_GC_Verifier(No_GC_Verifier * ngcv);
+~Pause_No_GC_Verifier();
+#else
+Pause_No_GC_Verifier(No_GC_Verifier * ngcv) {}
+~Pause_No_GC_Verifier() {}
+#endif
+};
+// A No_Safepoint_Verifier object will throw an assertion failure if
+// the current thread passes a possible safepoint while this object is
+// instantiated. A safepoint, will either be: an oop allocation, blocking
+// on a Mutex or JavaLock, or executing a VM operation.
+//
+// If StrictSafepointChecks is turned off, it degrades into a No_GC_Verifier
+//
+class No_Safepoint_Verifier : public No_GC_Verifier {
+friend class Pause_No_Safepoint_Verifier;
+private:
+bool _activated;
+Thread *_thread;
+public:
+#ifdef ASSERT
+No_Safepoint_Verifier(bool activated = true, bool verifygc = true ) : No_GC_Verifier(verifygc) {
+_thread = Thread::current();
+if (_activated) {
+_thread->_allow_allocation_count++;
+_thread->_allow_safepoint_count++;
+}
+}
+~No_Safepoint_Verifier() {
+if (_activated) {
+_thread->_allow_allocation_count--;
+_thread->_allow_safepoint_count--;
+}
+}
+#else
+No_Safepoint_Verifier(bool activated = true, bool verifygc = true) : No_GC_Verifier(verifygc){}
+~No_Safepoint_Verifier() {}
+#endif
+};
+// A Pause_No_Safepoint_Verifier is used to temporarily pause the
+// behavior of a No_Safepoint_Verifier object. If we are not in debug
+// mode then there is nothing to do. If the No_Safepoint_Verifier
+// object has an _activated value of false, then there is nothing to
+// do for safepoint and allocation checking, but there may still be
+// something to do for the underlying No_GC_Verifier object.
+class Pause_No_Safepoint_Verifier : public Pause_No_GC_Verifier {
+private:
+No_Safepoint_Verifier * _nsv;
+public:
+#ifdef ASSERT
+Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv)
+: Pause_No_GC_Verifier(nsv) {
+_nsv = nsv;
+if (_nsv->_activated) {
+_nsv->_thread->_allow_allocation_count--;
+_nsv->_thread->_allow_safepoint_count--;
+}
+}
+~Pause_No_Safepoint_Verifier() {
+if (_nsv->_activated) {
+_nsv->_thread->_allow_allocation_count++;
+_nsv->_thread->_allow_safepoint_count++;
+}
+}
+#else
+Pause_No_Safepoint_Verifier(No_Safepoint_Verifier * nsv)
+: Pause_No_GC_Verifier(nsv) {}
+~Pause_No_Safepoint_Verifier() {}
+#endif
+};
+// JRT_LEAF currently can be called from either _thread_in_Java or
+// _thread_in_native mode. In _thread_in_native, it is ok
+// for another thread to trigger GC. The rest of the JRT_LEAF
+// rules apply.
+class JRT_Leaf_Verifier : public No_Safepoint_Verifier {
+static bool should_verify_GC();
+public:
+#ifdef ASSERT
+JRT_Leaf_Verifier();
+~JRT_Leaf_Verifier();
+#else
+JRT_Leaf_Verifier() {}
+~JRT_Leaf_Verifier() {}
+#endif
+};
+// A No_Alloc_Verifier object can be placed in methods where one assumes that
+// no allocation will occur. The destructor will verify this property
+// unless the constructor is called with argument false (not activated).
+//
+// The check will only be done in debug mode and if activated.
+// Note: this only makes sense at safepoints (otherwise, other threads may
+// allocate concurrently.)
+class No_Alloc_Verifier : public StackObj {
+private:
+bool  _activated;
+public:
+#ifdef ASSERT
+No_Alloc_Verifier(bool activated = true) {
+_activated = activated;
+if (_activated) Thread::current()->_allow_allocation_count++;
+}
+~No_Alloc_Verifier() {
+if (_activated) Thread::current()->_allow_allocation_count--;
+}
+#else
+No_Alloc_Verifier(bool activated = true) {}
+~No_Alloc_Verifier() {}
+#endif
+};

Mercurial > hg > graal-jvmci-8

comparison src/share/vm/memory/gcLocker.hpp @ 0:a61af66fc99e jdk7-b24