diff --git a/src/hotspot/.mx.jvmci/.project b/src/hotspot/.mx.jvmci/.project deleted file mode 100644 index 5d4c97b68bc..00000000000 --- a/src/hotspot/.mx.jvmci/.project +++ /dev/null @@ -1,18 +0,0 @@ - - - mx.jvmci - - - mx - - - - org.python.pydev.PyDevBuilder - - - - - - org.python.pydev.pythonNature - - diff --git a/src/hotspot/.mx.jvmci/.pydevproject b/src/hotspot/.mx.jvmci/.pydevproject deleted file mode 100644 index 3f852ee834a..00000000000 --- a/src/hotspot/.mx.jvmci/.pydevproject +++ /dev/null @@ -1,12 +0,0 @@ - - -Default -python 2.7 - -/mx.jvmci - - -/mx - - - diff --git a/src/hotspot/share/code/nmethod.cpp b/src/hotspot/share/code/nmethod.cpp index 9a1559f53df..412331bdad0 100644 --- a/src/hotspot/share/code/nmethod.cpp +++ b/src/hotspot/share/code/nmethod.cpp @@ -409,6 +409,7 @@ void nmethod::init_defaults() { #if INCLUDE_JVMCI _jvmci_installed_code = NULL; _speculation_log = NULL; + _jvmci_installed_code_triggers_unloading = false; #endif } @@ -461,8 +462,8 @@ nmethod* nmethod::new_nmethod(const methodHandle& method, AbstractCompiler* compiler, int comp_level #if INCLUDE_JVMCI - , Handle installed_code, - Handle speculationLog + , jweak installed_code, + jweak speculationLog #endif ) { @@ -642,8 +643,8 @@ nmethod::nmethod( AbstractCompiler* compiler, int comp_level #if INCLUDE_JVMCI - , Handle installed_code, - Handle speculation_log + , jweak installed_code, + jweak speculation_log #endif ) : CompiledMethod(method, "nmethod", type, nmethod_size, sizeof(nmethod), code_buffer, offsets->value(CodeOffsets::Frame_Complete), frame_size, oop_maps, false), @@ -671,8 +672,14 @@ nmethod::nmethod( set_ctable_begin(header_begin() + _consts_offset); #if INCLUDE_JVMCI - _jvmci_installed_code = installed_code(); - _speculation_log = (instanceOop)speculation_log(); + _jvmci_installed_code = installed_code; + _speculation_log = speculation_log; + oop obj = JNIHandles::resolve(installed_code); + if (obj == NULL || (obj->is_a(HotSpotNmethod::klass()) && HotSpotNmethod::isDefault(obj))) { + _jvmci_installed_code_triggers_unloading = false; + } else { + _jvmci_installed_code_triggers_unloading = true; + } if (compiler->is_jvmci()) { // JVMCI might not produce any stub sections @@ -1026,8 +1033,6 @@ void nmethod::make_unloaded(BoolObjectClosure* is_alive, oop cause) { " unloadable, Method*(" INTPTR_FORMAT "), cause(" INTPTR_FORMAT ")", p2i(this), p2i(_method), p2i(cause)); - if (!Universe::heap()->is_gc_active()) - cause->klass()->print_on(&ls); } // Unlink the osr method, so we do not look this up again if (is_osr_method()) { @@ -1077,14 +1082,8 @@ void nmethod::make_unloaded(BoolObjectClosure* is_alive, oop cause) { #if INCLUDE_JVMCI // The method can only be unloaded after the pointer to the installed code // Java wrapper is no longer alive. Here we need to clear out this weak - // reference to the dead object. Nulling out the reference has to happen - // after the method is unregistered since the original value may be still - // tracked by the rset. + // reference to the dead object. maybe_invalidate_installed_code(); - // Clear these out after the nmethod has been unregistered and any - // updates to the InstalledCode instance have been performed. - _jvmci_installed_code = NULL; - _speculation_log = NULL; #endif // The Method* is gone at this point @@ -1246,10 +1245,6 @@ bool nmethod::make_not_entrant_or_zombie(unsigned int state) { MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag); if (nmethod_needs_unregister) { Universe::heap()->unregister_nmethod(this); -#ifdef JVMCI - _jvmci_installed_code = NULL; - _speculation_log = NULL; -#endif } flush_dependencies(NULL); } @@ -1314,6 +1309,11 @@ void nmethod::flush() { CodeCache::drop_scavenge_root_nmethod(this); } +#if INCLUDE_JVMCI + assert(_jvmci_installed_code == NULL, "should have been nulled out when transitioned to zombie"); + assert(_speculation_log == NULL, "should have been nulled out when transitioned to zombie"); +#endif + CodeBlob::flush(); CodeCache::free(this); } @@ -1500,29 +1500,18 @@ bool nmethod::do_unloading_oops(address low_boundary, BoolObjectClosure* is_aliv #if INCLUDE_JVMCI bool nmethod::do_unloading_jvmci(BoolObjectClosure* is_alive, bool unloading_occurred) { - bool is_unloaded = false; - // Follow JVMCI method - BarrierSet* bs = Universe::heap()->barrier_set(); if (_jvmci_installed_code != NULL) { - if (_jvmci_installed_code->is_a(HotSpotNmethod::klass()) && HotSpotNmethod::isDefault(_jvmci_installed_code)) { - if (!is_alive->do_object_b(_jvmci_installed_code)) { + if (JNIHandles::is_global_weak_cleared(_jvmci_installed_code)) { + if (_jvmci_installed_code_triggers_unloading) { + // jweak reference processing has already cleared the referent + make_unloaded(is_alive, NULL); + return true; + } else { clear_jvmci_installed_code(); } - } else { - if (can_unload(is_alive, (oop*)&_jvmci_installed_code, unloading_occurred)) { - return true; - } } } - - if (_speculation_log != NULL) { - if (!is_alive->do_object_b(_speculation_log)) { - bs->write_ref_nmethod_pre(&_speculation_log, this); - _speculation_log = NULL; - bs->write_ref_nmethod_post(&_speculation_log, this); - } - } - return is_unloaded; + return false; } #endif @@ -1594,15 +1583,6 @@ void nmethod::oops_do(OopClosure* f, bool allow_zombie) { // (See comment above.) } -#if INCLUDE_JVMCI - if (_jvmci_installed_code != NULL) { - f->do_oop((oop*) &_jvmci_installed_code); - } - if (_speculation_log != NULL) { - f->do_oop((oop*) &_speculation_log); - } -#endif - RelocIterator iter(this, low_boundary); while (iter.next()) { @@ -2860,44 +2840,50 @@ void nmethod::print_statistics() { #if INCLUDE_JVMCI void nmethod::clear_jvmci_installed_code() { - // write_ref_method_pre/post can only be safely called at a - // safepoint or while holding the CodeCache_lock - assert(CodeCache_lock->is_locked() || - SafepointSynchronize::is_at_safepoint(), "should be performed under a lock for consistency"); + assert_locked_or_safepoint(Patching_lock); if (_jvmci_installed_code != NULL) { - // This must be done carefully to maintain nmethod remembered sets properly - BarrierSet* bs = Universe::heap()->barrier_set(); - bs->write_ref_nmethod_pre(&_jvmci_installed_code, this); + JNIHandles::destroy_weak_global(_jvmci_installed_code); _jvmci_installed_code = NULL; - bs->write_ref_nmethod_post(&_jvmci_installed_code, this); + } +} + +void nmethod::clear_speculation_log() { + assert_locked_or_safepoint(Patching_lock); + if (_speculation_log != NULL) { + JNIHandles::destroy_weak_global(_speculation_log); + _speculation_log = NULL; } } void nmethod::maybe_invalidate_installed_code() { assert(Patching_lock->is_locked() || SafepointSynchronize::is_at_safepoint(), "should be performed under a lock for consistency"); - oop installed_code = jvmci_installed_code(); + oop installed_code = JNIHandles::resolve(_jvmci_installed_code); if (installed_code != NULL) { + // Update the values in the InstalledCode instance if it still refers to this nmethod nmethod* nm = (nmethod*)InstalledCode::address(installed_code); - if (nm == NULL || nm != this) { - // The link has been broken or the InstalledCode instance is - // associated with another nmethod so do nothing. - return; - } - if (!is_alive()) { - // Break the link between nmethod and InstalledCode such that the nmethod - // can subsequently be flushed safely. The link must be maintained while - // the method could have live activations since invalidateInstalledCode - // might want to invalidate all existing activations. - InstalledCode::set_address(installed_code, 0); - InstalledCode::set_entryPoint(installed_code, 0); - } else if (is_not_entrant()) { - // Remove the entry point so any invocation will fail but keep - // the address link around that so that existing activations can - // be invalidated. - InstalledCode::set_entryPoint(installed_code, 0); + if (nm == this) { + if (!is_alive()) { + // Break the link between nmethod and InstalledCode such that the nmethod + // can subsequently be flushed safely. The link must be maintained while + // the method could have live activations since invalidateInstalledCode + // might want to invalidate all existing activations. + InstalledCode::set_address(installed_code, 0); + InstalledCode::set_entryPoint(installed_code, 0); + } else if (is_not_entrant()) { + // Remove the entry point so any invocation will fail but keep + // the address link around that so that existing activations can + // be invalidated. + InstalledCode::set_entryPoint(installed_code, 0); + } } } + if (!is_alive()) { + // Clear these out after the nmethod has been unregistered and any + // updates to the InstalledCode instance have been performed. + clear_jvmci_installed_code(); + clear_speculation_log(); + } } void nmethod::invalidate_installed_code(Handle installedCode, TRAPS) { @@ -2916,45 +2902,49 @@ void nmethod::invalidate_installed_code(Handle installedCode, TRAPS) { { MutexLockerEx pl(Patching_lock, Mutex::_no_safepoint_check_flag); // This relationship can only be checked safely under a lock - assert(nm == NULL || !nm->is_alive() || nm->jvmci_installed_code() == installedCode(), "sanity check"); + assert(!nm->is_alive() || nm->jvmci_installed_code() == installedCode(), "sanity check"); } #endif if (nm->is_alive()) { - // The nmethod state machinery maintains the link between the - // HotSpotInstalledCode and nmethod* so as long as the nmethod appears to be - // alive assume there is work to do and deoptimize the nmethod. + // Invalidating the InstalledCode means we want the nmethod + // to be deoptimized. nm->mark_for_deoptimization(); VM_Deoptimize op; VMThread::execute(&op); } + // Multiple threads could reach this point so we now need to + // lock and re-check the link to the nmethod so that only one + // thread clears it. MutexLockerEx pl(Patching_lock, Mutex::_no_safepoint_check_flag); - // Check that it's still associated with the same nmethod and break - // the link if it is. if (InstalledCode::address(installedCode) == nativeMethod) { - InstalledCode::set_address(installedCode, 0); + InstalledCode::set_address(installedCode, 0); } } +oop nmethod::jvmci_installed_code() { + return JNIHandles::resolve(_jvmci_installed_code); +} + +oop nmethod::speculation_log() { + return JNIHandles::resolve(_speculation_log); +} + char* nmethod::jvmci_installed_code_name(char* buf, size_t buflen) { if (!this->is_compiled_by_jvmci()) { return NULL; } - oop installedCode = this->jvmci_installed_code(); - if (installedCode != NULL) { - oop installedCodeName = NULL; - if (installedCode->is_a(InstalledCode::klass())) { - installedCodeName = InstalledCode::name(installedCode); + oop installed_code = JNIHandles::resolve(_jvmci_installed_code); + if (installed_code != NULL) { + oop installed_code_name = NULL; + if (installed_code->is_a(InstalledCode::klass())) { + installed_code_name = InstalledCode::name(installed_code); } - if (installedCodeName != NULL) { - return java_lang_String::as_utf8_string(installedCodeName, buf, (int)buflen); - } else { - jio_snprintf(buf, buflen, "null"); - return buf; + if (installed_code_name != NULL) { + return java_lang_String::as_utf8_string(installed_code_name, buf, (int)buflen); } } - jio_snprintf(buf, buflen, "noInstalledCode"); - return buf; + return NULL; } #endif diff --git a/src/hotspot/share/code/nmethod.hpp b/src/hotspot/share/code/nmethod.hpp index 600c34fcb23..73fe7e236ec 100644 --- a/src/hotspot/share/code/nmethod.hpp +++ b/src/hotspot/share/code/nmethod.hpp @@ -63,9 +63,22 @@ class nmethod : public CompiledMethod { jmethodID _jmethod_id; // Cache of method()->jmethod_id() #if INCLUDE_JVMCI - // Needed to keep nmethods alive that are not the default nmethod for the associated Method. - oop _jvmci_installed_code; - oop _speculation_log; + // A weak reference to an InstalledCode object associated with + // this nmethod. + jweak _jvmci_installed_code; + + // A weak reference to a SpeculationLog object associated with + // this nmethod. + jweak _speculation_log; + + // Determines whether this nmethod is unloaded when the + // referent in _jvmci_installed_code is cleared. This + // will be false if the referent is initialized to a + // HotSpotNMethod object whose isDefault field is true. + // That is, installed code other than a "default" + // HotSpotNMethod causes nmethod unloading. + // This field is ignored once _jvmci_installed_code is NULL. + bool _jvmci_installed_code_triggers_unloading; #endif // To support simple linked-list chaining of nmethods: @@ -192,8 +205,8 @@ class nmethod : public CompiledMethod { AbstractCompiler* compiler, int comp_level #if INCLUDE_JVMCI - , Handle installed_code, - Handle speculation_log + , jweak installed_code, + jweak speculation_log #endif ); @@ -236,8 +249,8 @@ class nmethod : public CompiledMethod { AbstractCompiler* compiler, int comp_level #if INCLUDE_JVMCI - , Handle installed_code = Handle(), - Handle speculation_log = Handle() + , jweak installed_code = NULL, + jweak speculation_log = NULL #endif ); @@ -433,27 +446,46 @@ public: void set_method(Method* method) { _method = method; } #if INCLUDE_JVMCI - oop jvmci_installed_code() { return _jvmci_installed_code ; } + // Gets the InstalledCode object associated with this nmethod + // which may be NULL if this nmethod was not compiled by JVMCI + // or the weak reference has been cleared. + oop jvmci_installed_code(); + + // Copies the value of the name field in the InstalledCode + // object (if any) associated with this nmethod into buf. + // Returns the value of buf if it was updated otherwise NULL. char* jvmci_installed_code_name(char* buf, size_t buflen); - // Update the state of any InstalledCode instance associated with + // Updates the state of the InstalledCode (if any) associated with // this nmethod based on the current value of _state. void maybe_invalidate_installed_code(); - // Helper function to invalidate InstalledCode instances + // Deoptimizes the nmethod (if any) in the address field of a given + // InstalledCode object. The address field is zeroed upon return. static void invalidate_installed_code(Handle installed_code, TRAPS); - oop speculation_log() { return _speculation_log ; } + // Gets the SpeculationLog object associated with this nmethod + // which may be NULL if this nmethod was not compiled by JVMCI + // or the weak reference has been cleared. + oop speculation_log(); private: + // Deletes the weak reference (if any) to the InstalledCode object + // associated with this nmethod. void clear_jvmci_installed_code(); + // Deletes the weak reference (if any) to the SpeculationLog object + // associated with this nmethod. + void clear_speculation_log(); + public: #endif protected: virtual bool do_unloading_oops(address low_boundary, BoolObjectClosure* is_alive, bool unloading_occurred); #if INCLUDE_JVMCI + // See comment for _jvmci_installed_code_triggers_unloading field. + // Returns whether this nmethod was unloaded. virtual bool do_unloading_jvmci(BoolObjectClosure* is_alive, bool unloading_occurred); #endif diff --git a/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.cpp b/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.cpp index c8ff35ddf63..4ed16f6e7a4 100644 --- a/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.cpp +++ b/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.cpp @@ -214,52 +214,3 @@ G1SATBCardTableLoggingModRefBS::invalidate(MemRegion mr) { } } } - -void G1SATBCardTableModRefBS::write_ref_nmethod_post(oop* dst, nmethod* nm) { - oop obj = oopDesc::load_heap_oop(dst); - if (obj != NULL) { - G1CollectedHeap* g1h = G1CollectedHeap::heap(); - HeapRegion* hr = g1h->heap_region_containing(obj); - hr->add_strong_code_root(nm); - } -} - -class G1EnsureLastRefToRegion : public OopClosure { - G1CollectedHeap* _g1h; - HeapRegion* _hr; - oop* _dst; - - bool _value; -public: - G1EnsureLastRefToRegion(G1CollectedHeap* g1h, HeapRegion* hr, oop* dst) : - _g1h(g1h), _hr(hr), _dst(dst), _value(true) {} - - void do_oop(oop* p) { - if (_value && p != _dst) { - oop obj = oopDesc::load_heap_oop(p); - if (obj != NULL) { - HeapRegion* hr = _g1h->heap_region_containing(obj); - if (hr == _hr) { - // Another reference to the same region. - _value = false; - } - } - } - } - void do_oop(narrowOop* p) { ShouldNotReachHere(); } - bool value() const { return _value; } -}; - -void G1SATBCardTableModRefBS::write_ref_nmethod_pre(oop* dst, nmethod* nm) { - oop obj = oopDesc::load_heap_oop(dst); - if (obj != NULL) { - G1CollectedHeap* g1h = G1CollectedHeap::heap(); - HeapRegion* hr = g1h->heap_region_containing(obj); - G1EnsureLastRefToRegion ensure_last_ref(g1h, hr, dst); - nm->oops_do(&ensure_last_ref); - if (ensure_last_ref.value()) { - // Last reference to this region, remove the nmethod from the rset. - hr->remove_strong_code_root(nm); - } - } -} diff --git a/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.hpp b/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.hpp index 65315484aeb..b1703f86880 100644 --- a/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.hpp +++ b/src/hotspot/share/gc/g1/g1SATBCardTableModRefBS.hpp @@ -95,9 +95,6 @@ public: jbyte val = _byte_map[card_index]; return (val & (clean_card_mask_val() | deferred_card_val())) == deferred_card_val(); } - virtual void write_ref_nmethod_pre(oop* dst, nmethod* nm); - virtual void write_ref_nmethod_post(oop* dst, nmethod* nm); - }; template<> diff --git a/src/hotspot/share/gc/shared/barrierSet.hpp b/src/hotspot/share/gc/shared/barrierSet.hpp index eaec4af4fcc..bd8a7e532a5 100644 --- a/src/hotspot/share/gc/shared/barrierSet.hpp +++ b/src/hotspot/share/gc/shared/barrierSet.hpp @@ -120,9 +120,6 @@ public: static void static_write_ref_array_pre(HeapWord* start, size_t count); static void static_write_ref_array_post(HeapWord* start, size_t count); - virtual void write_ref_nmethod_pre(oop* dst, nmethod* nm) {} - virtual void write_ref_nmethod_post(oop* dst, nmethod* nm) {} - protected: virtual void write_ref_array_work(MemRegion mr) = 0; diff --git a/src/hotspot/share/jvmci/jvmciCompilerToVM.cpp b/src/hotspot/share/jvmci/jvmciCompilerToVM.cpp index 46fb9a650a3..a01da7b52cc 100644 --- a/src/hotspot/share/jvmci/jvmciCompilerToVM.cpp +++ b/src/hotspot/share/jvmci/jvmciCompilerToVM.cpp @@ -1039,7 +1039,7 @@ C2V_VMENTRY(jint, installCode, (JNIEnv *jniEnv, jobject, jobject target, jobject if (result != JVMCIEnv::ok) { assert(cb == NULL, "should be"); } else { - if (!installed_code_handle.is_null()) { + if (installed_code_handle.not_null()) { assert(installed_code_handle->is_a(InstalledCode::klass()), "wrong type"); nmethod::invalidate_installed_code(installed_code_handle, CHECK_0); { @@ -1058,13 +1058,6 @@ C2V_VMENTRY(jint, installCode, (JNIEnv *jniEnv, jobject, jobject target, jobject HotSpotInstalledCode::set_codeSize(installed_code_handle, cb->code_size()); } } - nmethod* nm = cb->as_nmethod_or_null(); - if (nm != NULL && installed_code_handle->is_scavengable()) { - assert(nm->detect_scavenge_root_oops(), "nm should be scavengable if installed_code is scavengable"); - if (!UseG1GC) { - assert(nm->on_scavenge_root_list(), "nm should be on scavengable list"); - } - } } } return result; diff --git a/src/hotspot/share/jvmci/jvmciEnv.cpp b/src/hotspot/share/jvmci/jvmciEnv.cpp index 320ecccd035..6c3b67701ab 100644 --- a/src/hotspot/share/jvmci/jvmciEnv.cpp +++ b/src/hotspot/share/jvmci/jvmciEnv.cpp @@ -521,7 +521,9 @@ JVMCIEnv::CodeInstallResult JVMCIEnv::register_method( debug_info, dependencies, code_buffer, frame_words, oop_map_set, handler_table, &implicit_tbl, - compiler, comp_level, installed_code, speculation_log); + compiler, comp_level, + JNIHandles::make_weak_global(installed_code), + JNIHandles::make_weak_global(speculation_log)); // Free codeBlobs //code_buffer->free_blob(); diff --git a/src/hotspot/share/runtime/deoptimization.cpp b/src/hotspot/share/runtime/deoptimization.cpp index 4197e87e723..087e26f5019 100644 --- a/src/hotspot/share/runtime/deoptimization.cpp +++ b/src/hotspot/share/runtime/deoptimization.cpp @@ -1674,19 +1674,9 @@ JRT_ENTRY(void, Deoptimization::uncommon_trap_inner(JavaThread* thread, jint tra tty->print(" compiler=%s compile_id=%d", nm->compiler_name(), nm->compile_id()); #if INCLUDE_JVMCI if (nm->is_nmethod()) { - oop installedCode = nm->as_nmethod()->jvmci_installed_code(); - if (installedCode != NULL) { - oop installedCodeName = NULL; - if (installedCode->is_a(InstalledCode::klass())) { - installedCodeName = InstalledCode::name(installedCode); - } - if (installedCodeName != NULL) { - tty->print(" (JVMCI: installedCodeName=%s) ", java_lang_String::as_utf8_string(installedCodeName)); - } else { - tty->print(" (JVMCI: installed code has no name) "); - } - } else if (nm->is_compiled_by_jvmci()) { - tty->print(" (JVMCI: no installed code) "); + char* installed_code_name = nm->as_nmethod()->jvmci_installed_code_name(buf, sizeof(buf)); + if (installed_code_name != NULL) { + tty->print(" (JVMCI: installed code name=%s) ", installed_code_name); } } #endif diff --git a/src/hotspot/share/runtime/jniHandles.cpp b/src/hotspot/share/runtime/jniHandles.cpp index 76f13e620da..8819f3c2cfc 100644 --- a/src/hotspot/share/runtime/jniHandles.cpp +++ b/src/hotspot/share/runtime/jniHandles.cpp @@ -127,6 +127,11 @@ oop JNIHandles::resolve_jweak(jweak handle) { template oop JNIHandles::resolve_jweak(jweak); template oop JNIHandles::resolve_jweak(jweak); +bool JNIHandles::is_global_weak_cleared(jweak handle) { + assert(is_jweak(handle), "not a weak handle"); + return guard_value(jweak_ref(handle)) == NULL; +} + void JNIHandles::destroy_global(jobject handle) { if (handle != NULL) { assert(is_global_handle(handle), "Invalid delete of global JNI handle"); diff --git a/src/hotspot/share/runtime/jniHandles.hpp b/src/hotspot/share/runtime/jniHandles.hpp index 71e65dd3491..b7cd7668549 100644 --- a/src/hotspot/share/runtime/jniHandles.hpp +++ b/src/hotspot/share/runtime/jniHandles.hpp @@ -82,6 +82,7 @@ class JNIHandles : AllStatic { // Weak global handles static jobject make_weak_global(Handle obj); static void destroy_weak_global(jobject handle); + static bool is_global_weak_cleared(jweak handle); // Test jweak without resolution // Sentinel marking deleted handles in block. Note that we cannot store NULL as // the sentinel, since clearing weak global JNI refs are done by storing NULL in diff --git a/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotNmethod.java b/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotNmethod.java index f8aa3cb9310..413ba290741 100644 --- a/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotNmethod.java +++ b/src/jdk.internal.vm.ci/share/classes/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotNmethod.java @@ -30,13 +30,10 @@ import jdk.vm.ci.meta.JavaType; import jdk.vm.ci.meta.ResolvedJavaMethod; /** - * Implementation of {@link InstalledCode} for code installed as an nmethod. The nmethod stores a - * weak reference to an instance of this class. This is necessary to keep the nmethod from being - * unloaded while the associated {@link HotSpotNmethod} instance is alive. - *

- * Note that there is no (current) way for the reference from an nmethod to a {@link HotSpotNmethod} - * instance to be anything but weak. This is due to the fact that HotSpot does not treat nmethods as - * strong GC roots. + * Implementation of {@link InstalledCode} for code installed as an nmethod. + * + * When a {@link HotSpotNmethod} dies, it triggers unloading of the nmethod unless + * {@link #isDefault() == true}. */ public class HotSpotNmethod extends HotSpotInstalledCode { @@ -54,6 +51,11 @@ public class HotSpotNmethod extends HotSpotInstalledCode { this.isDefault = isDefault; } + /** + * Determines if the nmethod associated with this object is the compiled entry point for + * {@link #getMethod()}. If {@code false}, then the nmethod is unloaded when the VM determines + * this object has died. + */ public boolean isDefault() { return isDefault; }