Mercurial > hg > graal-compiler
view src/share/vm/memory/gcLocker.hpp @ 599:0ad1cb407fa1
6805427: adlc compiler may generate incorrect machnode emission code
Reviewed-by: kvn, twisti
author | never |
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date | Wed, 25 Feb 2009 10:53:14 -0800 |
parents | d1605aabd0a1 |
children | 821269eca479 |
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/* * Copyright 1997-2008 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), _activated(activated) { _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 };