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This commit is contained in:
Karen Kinnear 2009-09-21 18:10:22 -04:00
commit 4e453ff713
4 changed files with 204 additions and 53 deletions

6
hotspot/src/share/vm/classfile/classFileParser.cpp

@ -3231,6 +3231,12 @@ instanceKlassHandle ClassFileParser::parseClassFile(symbolHandle name,
this_klass->set_has_final_method();
}
this_klass->set_method_ordering(method_ordering());
// The instanceKlass::_methods_jmethod_ids cache and the
// instanceKlass::_methods_cached_itable_indices cache are
// both managed on the assumption that the initial cache
// size is equal to the number of methods in the class. If
// that changes, then instanceKlass::idnum_can_increment()
// has to be changed accordingly.
this_klass->set_initial_method_idnum(methods->length());
this_klass->set_name(cp->klass_name_at(this_class_index));
if (LinkWellKnownClasses || is_anonymous()) // I am well known to myself

229
hotspot/src/share/vm/oops/instanceKlass.cpp

@ -967,33 +967,78 @@ JNIid* instanceKlass::jni_id_for(int offset) {
// Lookup or create a jmethodID.
// This code can be called by the VM thread. For this reason it is critical that
// there are no blocking operations (safepoints) while the lock is held -- or a
// deadlock can occur.
jmethodID instanceKlass::jmethod_id_for_impl(instanceKlassHandle ik_h, methodHandle method_h) {
// This code is called by the VMThread and JavaThreads so the
// locking has to be done very carefully to avoid deadlocks
// and/or other cache consistency problems.
//
jmethodID instanceKlass::get_jmethod_id(instanceKlassHandle ik_h, methodHandle method_h) {
size_t idnum = (size_t)method_h->method_idnum();
jmethodID* jmeths = ik_h->methods_jmethod_ids_acquire();
size_t length = 0;
jmethodID id = NULL;
// array length stored in first element, other elements offset by one
if (jmeths == NULL || // If there is no jmethodID array,
(length = (size_t)jmeths[0]) <= idnum || // or if it is too short,
(id = jmeths[idnum+1]) == NULL) { // or if this jmethodID isn't allocated
// Do all the safepointing things (allocations) before grabbing the lock.
// These allocations will have to be freed if they are unused.
// We use a double-check locking idiom here because this cache is
// performance sensitive. In the normal system, this cache only
// transitions from NULL to non-NULL which is safe because we use
// release_set_methods_jmethod_ids() to advertise the new cache.
// A partially constructed cache should never be seen by a racing
// thread. We also use release_store_ptr() to save a new jmethodID
// in the cache so a partially constructed jmethodID should never be
// seen either. Cache reads of existing jmethodIDs proceed without a
// lock, but cache writes of a new jmethodID requires uniqueness and
// creation of the cache itself requires no leaks so a lock is
// generally acquired in those two cases.
//
// If the RedefineClasses() API has been used, then this cache can
// grow and we'll have transitions from non-NULL to bigger non-NULL.
// Cache creation requires no leaks and we require safety between all
// cache accesses and freeing of the old cache so a lock is generally
// acquired when the RedefineClasses() API has been used.
// Allocate a new array of methods.
if (jmeths != NULL) {
// the cache already exists
if (!ik_h->idnum_can_increment()) {
// the cache can't grow so we can just get the current values
get_jmethod_id_length_value(jmeths, idnum, &length, &id);
} else {
// cache can grow so we have to be more careful
if (Threads::number_of_threads() == 0 ||
SafepointSynchronize::is_at_safepoint()) {
// we're single threaded or at a safepoint - no locking needed
get_jmethod_id_length_value(jmeths, idnum, &length, &id);
} else {
MutexLocker ml(JmethodIdCreation_lock);
get_jmethod_id_length_value(jmeths, idnum, &length, &id);
}
}
}
// implied else:
// we need to allocate a cache so default length and id values are good
if (jmeths == NULL || // no cache yet
length <= idnum || // cache is too short
id == NULL) { // cache doesn't contain entry
// This function can be called by the VMThread so we have to do all
// things that might block on a safepoint before grabbing the lock.
// Otherwise, we can deadlock with the VMThread or have a cache
// consistency issue. These vars keep track of what we might have
// to free after the lock is dropped.
jmethodID to_dealloc_id = NULL;
jmethodID* to_dealloc_jmeths = NULL;
// may not allocate new_jmeths or use it if we allocate it
jmethodID* new_jmeths = NULL;
if (length <= idnum) {
// A new array will be needed (unless some other thread beats us to it)
// allocate a new cache that might be used
size_t size = MAX2(idnum+1, (size_t)ik_h->idnum_allocated_count());
new_jmeths = NEW_C_HEAP_ARRAY(jmethodID, size+1);
memset(new_jmeths, 0, (size+1)*sizeof(jmethodID));
new_jmeths[0] =(jmethodID)size; // array size held in the first element
// cache size is stored in element[0], other elements offset by one
new_jmeths[0] = (jmethodID)size;
}
// Allocate a new method ID.
// allocate a new jmethodID that might be used
jmethodID new_id = NULL;
if (method_h->is_old() && !method_h->is_obsolete()) {
// The method passed in is old (but not obsolete), we need to use the current version
@ -1007,63 +1052,111 @@ jmethodID instanceKlass::jmethod_id_for_impl(instanceKlassHandle ik_h, methodHan
new_id = JNIHandles::make_jmethod_id(method_h);
}
if (Threads::number_of_threads() == 0 || SafepointSynchronize::is_at_safepoint()) {
// No need and unsafe to lock the JmethodIdCreation_lock at safepoint.
id = get_jmethod_id(ik_h, idnum, new_id, new_jmeths);
if (Threads::number_of_threads() == 0 ||
SafepointSynchronize::is_at_safepoint()) {
// we're single threaded or at a safepoint - no locking needed
id = get_jmethod_id_fetch_or_update(ik_h, idnum, new_id, new_jmeths,
&to_dealloc_id, &to_dealloc_jmeths);
} else {
MutexLocker ml(JmethodIdCreation_lock);
id = get_jmethod_id(ik_h, idnum, new_id, new_jmeths);
id = get_jmethod_id_fetch_or_update(ik_h, idnum, new_id, new_jmeths,
&to_dealloc_id, &to_dealloc_jmeths);
}
// The lock has been dropped so we can free resources.
// Free up either the old cache or the new cache if we allocated one.
if (to_dealloc_jmeths != NULL) {
FreeHeap(to_dealloc_jmeths);
}
// free up the new ID since it wasn't needed
if (to_dealloc_id != NULL) {
JNIHandles::destroy_jmethod_id(to_dealloc_id);
}
}
return id;
}
jmethodID instanceKlass::get_jmethod_id(instanceKlassHandle ik_h, size_t idnum,
jmethodID new_id, jmethodID* new_jmeths) {
// Retry lookup after we got the lock or ensured we are at safepoint
jmethodID* jmeths = ik_h->methods_jmethod_ids_acquire();
jmethodID id = NULL;
jmethodID to_dealloc_id = NULL;
jmethodID* to_dealloc_jmeths = NULL;
size_t length;
// Common code to fetch the jmethodID from the cache or update the
// cache with the new jmethodID. This function should never do anything
// that causes the caller to go to a safepoint or we can deadlock with
// the VMThread or have cache consistency issues.
//
jmethodID instanceKlass::get_jmethod_id_fetch_or_update(
instanceKlassHandle ik_h, size_t idnum, jmethodID new_id,
jmethodID* new_jmeths, jmethodID* to_dealloc_id_p,
jmethodID** to_dealloc_jmeths_p) {
assert(new_id != NULL, "sanity check");
assert(to_dealloc_id_p != NULL, "sanity check");
assert(to_dealloc_jmeths_p != NULL, "sanity check");
assert(Threads::number_of_threads() == 0 ||
SafepointSynchronize::is_at_safepoint() ||
JmethodIdCreation_lock->owned_by_self(), "sanity check");
if (jmeths == NULL || (length = (size_t)jmeths[0]) <= idnum) {
// reacquire the cache - we are locked, single threaded or at a safepoint
jmethodID* jmeths = ik_h->methods_jmethod_ids_acquire();
jmethodID id = NULL;
size_t length = 0;
if (jmeths == NULL || // no cache yet
(length = (size_t)jmeths[0]) <= idnum) { // cache is too short
if (jmeths != NULL) {
// We have grown the array: copy the existing entries, and delete the old array
// copy any existing entries from the old cache
for (size_t index = 0; index < length; index++) {
new_jmeths[index+1] = jmeths[index+1];
}
to_dealloc_jmeths = jmeths; // using the new jmeths, deallocate the old one
*to_dealloc_jmeths_p = jmeths; // save old cache for later delete
}
ik_h->release_set_methods_jmethod_ids(jmeths = new_jmeths);
} else {
// fetch jmethodID (if any) from the existing cache
id = jmeths[idnum+1];
to_dealloc_jmeths = new_jmeths; // using the old jmeths, deallocate the new one
*to_dealloc_jmeths_p = new_jmeths; // save new cache for later delete
}
if (id == NULL) {
// No matching jmethodID in the existing cache or we have a new
// cache or we just grew the cache. This cache write is done here
// by the first thread to win the foot race because a jmethodID
// needs to be unique once it is generally available.
id = new_id;
jmeths[idnum+1] = id; // install the new method ID
} else {
to_dealloc_id = new_id; // the new id wasn't used, mark it for deallocation
}
// Free up unneeded or no longer needed resources
FreeHeap(to_dealloc_jmeths);
if (to_dealloc_id != NULL) {
JNIHandles::destroy_jmethod_id(to_dealloc_id);
// The jmethodID cache can be read while unlocked so we have to
// make sure the new jmethodID is complete before installing it
// in the cache.
OrderAccess::release_store_ptr(&jmeths[idnum+1], id);
} else {
*to_dealloc_id_p = new_id; // save new id for later delete
}
return id;
}
// Common code to get the jmethodID cache length and the jmethodID
// value at index idnum if there is one.
//
void instanceKlass::get_jmethod_id_length_value(jmethodID* cache,
size_t idnum, size_t *length_p, jmethodID* id_p) {
assert(cache != NULL, "sanity check");
assert(length_p != NULL, "sanity check");
assert(id_p != NULL, "sanity check");
// cache size is stored in element[0], other elements offset by one
*length_p = (size_t)cache[0];
if (*length_p <= idnum) { // cache is too short
*id_p = NULL;
} else {
*id_p = cache[idnum+1]; // fetch jmethodID (if any)
}
}
// Lookup a jmethodID, NULL if not found. Do no blocking, no allocations, no handles
jmethodID instanceKlass::jmethod_id_or_null(methodOop method) {
size_t idnum = (size_t)method->method_idnum();
jmethodID* jmeths = methods_jmethod_ids_acquire();
size_t length; // length assigned as debugging crumb
jmethodID id = NULL;
if (jmeths != NULL && // If there is a jmethodID array,
if (jmeths != NULL && // If there is a cache
(length = (size_t)jmeths[0]) > idnum) { // and if it is long enough,
id = jmeths[idnum+1]; // Look up the id (may be NULL)
}
@ -1074,19 +1167,35 @@ jmethodID instanceKlass::jmethod_id_or_null(methodOop method) {
// Cache an itable index
void instanceKlass::set_cached_itable_index(size_t idnum, int index) {
int* indices = methods_cached_itable_indices_acquire();
if (indices == NULL || // If there is no index array,
((size_t)indices[0]) <= idnum) { // or if it is too short
// Lock before we allocate the array so we don't leak
int* to_dealloc_indices = NULL;
// We use a double-check locking idiom here because this cache is
// performance sensitive. In the normal system, this cache only
// transitions from NULL to non-NULL which is safe because we use
// release_set_methods_cached_itable_indices() to advertise the
// new cache. A partially constructed cache should never be seen
// by a racing thread. Cache reads and writes proceed without a
// lock, but creation of the cache itself requires no leaks so a
// lock is generally acquired in that case.
//
// If the RedefineClasses() API has been used, then this cache can
// grow and we'll have transitions from non-NULL to bigger non-NULL.
// Cache creation requires no leaks and we require safety between all
// cache accesses and freeing of the old cache so a lock is generally
// acquired when the RedefineClasses() API has been used.
if (indices == NULL || idnum_can_increment()) {
// we need a cache or the cache can grow
MutexLocker ml(JNICachedItableIndex_lock);
// Retry lookup after we got the lock
// reacquire the cache to see if another thread already did the work
indices = methods_cached_itable_indices_acquire();
size_t length = 0;
// array length stored in first element, other elements offset by one
// cache size is stored in element[0], other elements offset by one
if (indices == NULL || (length = (size_t)indices[0]) <= idnum) {
size_t size = MAX2(idnum+1, (size_t)idnum_allocated_count());
int* new_indices = NEW_C_HEAP_ARRAY(int, size+1);
new_indices[0] =(int)size; // array size held in the first element
// Copy the existing entries, if any
new_indices[0] = (int)size;
// copy any existing entries
size_t i;
for (i = 0; i < length; i++) {
new_indices[i+1] = indices[i+1];
@ -1096,15 +1205,32 @@ void instanceKlass::set_cached_itable_index(size_t idnum, int index) {
new_indices[i+1] = -1;
}
if (indices != NULL) {
FreeHeap(indices); // delete any old indices
// We have an old cache to delete so save it for after we
// drop the lock.
to_dealloc_indices = indices;
}
release_set_methods_cached_itable_indices(indices = new_indices);
}
if (idnum_can_increment()) {
// this cache can grow so we have to write to it safely
indices[idnum+1] = index;
}
} else {
CHECK_UNHANDLED_OOPS_ONLY(Thread::current()->clear_unhandled_oops());
}
// This is a cache, if there is a race to set it, it doesn't matter
indices[idnum+1] = index;
if (!idnum_can_increment()) {
// The cache cannot grow and this JNI itable index value does not
// have to be unique like a jmethodID. If there is a race to set it,
// it doesn't matter.
indices[idnum+1] = index;
}
if (to_dealloc_indices != NULL) {
// we allocated a new cache so free the old one
FreeHeap(to_dealloc_indices);
}
}
@ -2300,6 +2426,11 @@ void instanceKlass::set_init_state(ClassState state) {
// Add an information node that contains weak references to the
// interesting parts of the previous version of the_class.
// This is also where we clean out any unused weak references.
// Note that while we delete nodes from the _previous_versions
// array, we never delete the array itself until the klass is
// unloaded. The has_been_redefined() query depends on that fact.
//
void instanceKlass::add_previous_version(instanceKlassHandle ikh,
BitMap* emcp_methods, int emcp_method_count) {
assert(Thread::current()->is_VM_thread(),

20
hotspot/src/share/vm/oops/instanceKlass.hpp

@ -465,6 +465,10 @@ class instanceKlass: public Klass {
// RedefineClasses() support for previous versions:
void add_previous_version(instanceKlassHandle ikh, BitMap *emcp_methods,
int emcp_method_count);
// If the _previous_versions array is non-NULL, then this klass
// has been redefined at least once even if we aren't currently
// tracking a previous version.
bool has_been_redefined() const { return _previous_versions != NULL; }
bool has_previous_version() const;
void init_previous_versions() {
_previous_versions = NULL;
@ -506,9 +510,14 @@ class instanceKlass: public Klass {
void set_bootstrap_method(oop mh) { oop_store(&_bootstrap_method, mh); }
// jmethodID support
static jmethodID get_jmethod_id(instanceKlassHandle ik_h, size_t idnum,
jmethodID new_id, jmethodID* new_jmeths);
static jmethodID jmethod_id_for_impl(instanceKlassHandle ik_h, methodHandle method_h);
static jmethodID get_jmethod_id(instanceKlassHandle ik_h,
methodHandle method_h);
static jmethodID get_jmethod_id_fetch_or_update(instanceKlassHandle ik_h,
size_t idnum, jmethodID new_id, jmethodID* new_jmeths,
jmethodID* to_dealloc_id_p,
jmethodID** to_dealloc_jmeths_p);
static void get_jmethod_id_length_value(jmethodID* cache, size_t idnum,
size_t *length_p, jmethodID* id_p);
jmethodID jmethod_id_or_null(methodOop method);
// cached itable index support
@ -754,6 +763,11 @@ private:
void set_init_thread(Thread *thread) { _init_thread = thread; }
u2 idnum_allocated_count() const { return _idnum_allocated_count; }
// The RedefineClasses() API can cause new method idnums to be needed
// which will cause the caches to grow. Safety requires different
// cache management logic if the caches can grow instead of just
// going from NULL to non-NULL.
bool idnum_can_increment() const { return has_been_redefined(); }
jmethodID* methods_jmethod_ids_acquire() const
{ return (jmethodID*)OrderAccess::load_ptr_acquire(&_methods_jmethod_ids); }
void release_set_methods_jmethod_ids(jmethodID* jmeths)

2
hotspot/src/share/vm/oops/methodOop.hpp

@ -555,7 +555,7 @@ class methodOopDesc : public oopDesc {
// Get this method's jmethodID -- allocate if it doesn't exist
jmethodID jmethod_id() { methodHandle this_h(this);
return instanceKlass::jmethod_id_for_impl(method_holder(), this_h); }
return instanceKlass::get_jmethod_id(method_holder(), this_h); }
// Lookup the jmethodID for this method. Return NULL if not found.
// NOTE that this function can be called from a signal handler