mozilla
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gecko-dev
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1. Fixing http://bugzilla.mozilla.org/show_bug.cgi?id=182028 

Now caching of the last access slot covers GetterSlot instances as well and getter is always called for such slots

2. Fixing a potential race condition in setBySetter when a setter slot becomes an ordinary slot in response to a setter returning a value.

During execution of setBySetter a different thread can see initial null value in slot.value instead of the result of setter call as it is possible that JVM will first update slot.flags and only then slot.value for that thread. The fix replaces the old getter slot  by an ordinary one under synchronized block for that I added new getSlotPosition method and updated the rest of code accordingly.
This commit is contained in:
igor%mir2.org 2002-12-03 12:38:55 +00:00
Родитель edc41a0968
Коммит 5aa3180827
1 изменённых файлов: 115 добавлений и 106 удалений
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221
js/rhino/src/org/mozilla/javascript/ScriptableObject.java
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@ -122,17 +122,16 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
public boolean has(String name, Scriptable start) {
// See comments in get about cache operations
Slot slot = lastAccess;
if (name == slot.stringKey && slot.wasDeleted == 0) {
return true;
}
slot = getSlot(name, name.hashCode(), false);
if (slot != null) {
// Update cache
if (name != slot.stringKey || slot.wasDeleted != 0) {
slot = getSlot(name, name.hashCode());
if (slot == null) {
return false;
}
slot.stringKey = name;
lastAccess = slot;
return true;
}
return false;
return true;
}
/**
@ -143,7 +142,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
* @return true if and only if the property was found in the object
*/
public boolean has(int index, Scriptable start) {
return getSlot(null, index, false) != null;
return getSlot(null, index) != null;
}
/**
@ -157,34 +156,29 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
* @return the value of the property (may be null), or NOT_FOUND
*/
public Object get(String name, Scriptable start) {
Slot slot = lastAccess; // Get local copy
if (name == slot.stringKey) {
// Cache match, check if it was not deleted
if (slot.wasDeleted == 0) { return slot.value; }
// Query last access cache and check that it was not deleted
Slot slot = lastAccess;
if (name != slot.stringKey || slot.wasDeleted != 0) {
slot = getSlot(name, name.hashCode());
if (slot == null) {
return Scriptable.NOT_FOUND;
}
// Update cache - here stringKey.equals(name) holds, but it can be
// that slot.stringKey != name. To make last name cache work, need
// to change the key
slot.stringKey = name;
lastAccess = slot;
}
int hashCode = name.hashCode();
slot = getSlot(name, hashCode, false);
if (slot == null) {
return Scriptable.NOT_FOUND;
}
else if ((slot.flags & Slot.HAS_GETTER) != 0) {
return getByGetter((GetterSlot) slot, name, start);
if ((slot.flags & Slot.HAS_GETTER) != 0) {
return getByGetter((GetterSlot) slot, start);
}
// Here stringKey.equals(name) holds, but it can be that
// slot.stringKey != name. To make last name cache work, need
// to change the key
slot.stringKey = name;
// Update cache.
lastAccess = slot;
return slot.value;
}
private Object getByGetter(GetterSlot slot,
String name, Scriptable start)
{
private Object getByGetter(GetterSlot slot, Scriptable start) {
try {
if (slot.delegateTo == null) {
// Walk the prototype chain to find an appropriate
@ -219,7 +213,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
* @return the value of the property (may be null), or NOT_FOUND
*/
public Object get(int index, Scriptable start) {
Slot slot = getSlot(null, index, false);
Slot slot = getSlot(null, index);
if (slot == null)
return Scriptable.NOT_FOUND;
return slot.value;
@ -244,7 +238,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
Slot slot = lastAccess; // Get local copy
if (name != slot.stringKey || slot.wasDeleted != 0) {
int hash = name.hashCode();
slot = getSlot(name, hash, false);
slot = getSlot(name, hash);
if (slot == null) {
if (start != this) {
start.put(name, start, value);
@ -252,67 +246,76 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
}
slot = getSlotToSet(name, hash);
}
// Note: cache is not updated in put
}
if ((slot.attributes & ScriptableObject.READONLY) != 0) {
return;
}
else if ((slot.flags & Slot.HAS_SETTER) != 0) {
setBySetter((GetterSlot)slot, name, start, value);
if ((slot.flags & Slot.HAS_SETTER) != 0) {
setBySetter((GetterSlot)slot, start, value);
return;
}
if (this == start) {
// Note: no cache update
slot.value = value;
} else {
start.put(name, start, value);
}
}
private void setBySetter(GetterSlot slot,
String name, Scriptable start, Object value)
{
Context cx = Context.getContext();
private void setBySetter(GetterSlot slot, Scriptable start, Object value) {
Object setterThis;
Object[] args;
Object setterResult;
try {
Class pTypes[] = slot.setter.getParameterTypes();
Class desired = pTypes[pTypes.length - 1];
Object actualArg
= FunctionObject.convertArg(cx, start, value, desired);
if (slot.delegateTo == null) {
// Walk the prototype chain to find an appropriate
// object to invoke the setter on.
Object[] arg = { actualArg };
Class clazz = slot.setter.getDeclaringClass();
while (!clazz.isInstance(start)) {
start = start.getPrototype();
if (start == null) {
start = this;
break;
}
Context cx = Context.getContext();
Class pTypes[] = slot.setter.getParameterTypes();
Class desired = pTypes[pTypes.length - 1];
Object actualArg
= FunctionObject.convertArg(cx, start, value, desired);
if (slot.delegateTo == null) {
// Walk the prototype chain to find an appropriate
// object to invoke the setter on.
Class clazz = slot.setter.getDeclaringClass();
while (!clazz.isInstance(start)) {
start = start.getPrototype();
if (start == null) {
start = this;
break;
}
setterResult = slot.setter.invoke(start, arg);
}
else {
Object[] args = { this, actualArg };
setterResult = slot.setter.invoke(slot.delegateTo, args);
}
setterThis = start;
args = new Object[] { actualArg };
} else {
setterThis = slot.delegateTo;
args = new Object[] { this, actualArg };
}
catch (InvocationTargetException e) {
try {
setterResult = slot.setter.invoke(setterThis, args);
} catch (InvocationTargetException e) {
throw WrappedException.wrapException(e);
}
catch (IllegalAccessException e) {
} catch (IllegalAccessException e) {
throw WrappedException.wrapException(e);
}
if (slot.setterReturnsValue) {
slot.value = setterResult;
if (!(setterResult instanceof Method)) {
slot.flags = 0;
// Replace Getter slot by a simple one
Slot replacement = new Slot();
replacement.intKey = slot.intKey;
replacement.stringKey = slot.stringKey;
replacement.attributes = slot.attributes;
replacement.value = setterResult;
synchronized (this) {
int i = getSlotPosition(slots, slot.stringKey, slot.intKey);
// Check slot was not deleted/replaced before synchronization
if (i >= 0 && slots[i] == slot) {
slots[i] = replacement;
}
}
}
}
/**
* Sets the value of the indexed property, creating it if need be.
*
@ -321,7 +324,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
* @param value value to set the property to
*/
public void put(int index, Scriptable start, Object value) {
Slot slot = getSlot(null, index, false);
Slot slot = getSlot(null, index);
if (slot == null) {
if (start != this) {
start.put(index, start, value);
@ -382,7 +385,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
public int getAttributes(String name, Scriptable start)
throws PropertyException
{
Slot slot = getSlot(name, name.hashCode(), false);
Slot slot = getSlot(name, name.hashCode());
if (slot == null) {
throw PropertyException.withMessage0("msg.prop.not.found");
}
@ -406,7 +409,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
public int getAttributes(int index, Scriptable start)
throws PropertyException
{
Slot slot = getSlot(null, index, false);
Slot slot = getSlot(null, index);
if (slot == null) {
throw PropertyException.withMessage0("msg.prop.not.found");
}
@ -442,7 +445,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
{
final int mask = READONLY | DONTENUM | PERMANENT;
attributes &= mask; // mask out unused bits
Slot slot = getSlot(name, name.hashCode(), false);
Slot slot = getSlot(name, name.hashCode());
if (slot == null) {
throw PropertyException.withMessage0("msg.prop.not.found");
}
@ -469,7 +472,7 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
{
final int mask = READONLY | DONTENUM | PERMANENT;
attributes &= mask; // mask out unused bits
Slot slot = getSlot(null, index, false);
Slot slot = getSlot(null, index);
if (slot == null) {
throw PropertyException.withMessage0("msg.prop.not.found");
}
@ -1604,44 +1607,35 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
Slot slot = slots[i];
if (slot == null || slot == REMOVED)
continue;
if ((slot.flags & slot.HAS_SETTER) != 0 && attribute == READONLY)
continue;
slot.attributes |= attribute;
}
}
private Slot getSlot(String id, int index, boolean shouldDelete) {
Slot[] slots = this.slots;
if (slots == null)
return null;
int start = (index & 0x7fffffff) % slots.length;
int i = start;
do {
Slot slot = slots[i];
if (slot == null)
return null;
if (slot != REMOVED && slot.intKey == index &&
(slot.stringKey == id || (id != null &&
id.equals(slot.stringKey))))
{
if (shouldDelete) {
if ((slot.attributes & PERMANENT) == 0) {
// Mark the slot as removed to handle a case when
// another thread manages to put just removed slot
// into lastAccess cache.
slot.wasDeleted = (byte)1;
slots[i] = REMOVED;
count--;
if (slot == lastAccess)
lastAccess = REMOVED;
}
private Slot getSlot(String id, int index) {
Slot[] slots = this.slots; // Get local copy
int i = getSlotPosition(slots, id, index);
return (i < 0) ? null : slots[i];
}
private static int getSlotPosition(Slot[] slots, String id, int index) {
if (slots != null) {
int start = (index & 0x7fffffff) % slots.length;
int i = start;
do {
Slot slot = slots[i];
if (slot == null)
break;
if (slot != REMOVED && slot.intKey == index &&
(slot.stringKey == id || (id != null &&
id.equals(slot.stringKey))))
{
return i;
}
return slot;
}
if (++i == slots.length)
i = 0;
} while (i != start);
return null;
if (++i == slots.length)
i = 0;
} while (i != start);
}
return -1;
}
// First search for the existing slot without using synchronization
@ -1737,7 +1731,22 @@ public abstract class ScriptableObject implements Scriptable, Serializable,
private synchronized void removeSlot(String name, int index) {
if (count < 0)
throw Context.reportRuntimeError0("msg.remove.sealed");
getSlot(name, index, true);
int i = getSlotPosition(slots, name, index);
if (i >= 0) {
Slot slot = slots[i];
if ((slot.attributes & PERMANENT) == 0) {
// Mark the slot as removed to handle a case when
// another thread manages to put just removed slot
// into lastAccess cache.
slot.wasDeleted = (byte)1;
slots[i] = REMOVED;
count--;
if (slot == lastAccess) {
lastAccess = REMOVED;
}
}
}
}
// Grow the hash table to accommodate new entries.