6ae8d18218
...content provider and updating its oom adj This introduces the concept of an "unstable" reference on a content provider. When holding such a reference (and no normal stable ref), the content provider dying will not cause the client process to be killed. This is used in ContentResolver.query(), .openAssetFileDescriptor(), and .openTypedAssetFileDescriptor() to first access the provider with an unstable reference, and if at the point of calling into the provider we find it is dead then acquiring a new stable reference and doing the operation again. Thus if the provider process dies at any point until we get the result back, our own process will not be killed and we can safely retry the operation. Arguably there is still the potential for a race -- if somehow the provider is killed way late by the OOM killer after the query or open has returned -- but this should now be *extremely* unlikely. We also continue to have the issue with the other calls, but these are much less critical, and the same model can't be used there (we wouldn't want to execute two insert operations for example). The implementation of this required some significant changes to the underlying plumbing of content providers, now keeping track of the two different reference counts, and managing them appropriately. To facilitate this, the activity manager now has a formal connection object for a client reference on a content provider, which hands to the application when opening the provider. These changes have allowed a lot of the code to be cleaned up and subtle issues closed. For example, when a process is crashing, we now have a much better idea of the state of content provider clients (olding a stable ref, unstable ref, or waiting for it to launch), so that we can correctly handle each of these. The client side code is also a fair amount cleaner, though in the future there is more than should be done. In particular, the two ProviderClientRecord and ProviderRefCount classes should be combined into one, part of which is exposed to the ContentResolver internal API as a reference on a content provider with methods for updating reference counts and such. Some day we'll do that. Change-Id: I87b10d1b67573ab899e09ca428f1b556fd669c8c
88 lines
2.5 KiB
Java
88 lines
2.5 KiB
Java
/*
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* Copyright (C) 2012 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.android.server.am;
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import android.os.Binder;
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/**
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* Represents a link between a content provider and client.
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*/
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public class ContentProviderConnection extends Binder {
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public final ContentProviderRecord provider;
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public final ProcessRecord client;
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public int stableCount;
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public int unstableCount;
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// The client of this connection is currently waiting for the provider to appear.
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// Protected by the provider lock.
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public boolean waiting;
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// The provider of this connection is now dead.
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public boolean dead;
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// For debugging.
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public int numStableIncs;
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public int numUnstableIncs;
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public ContentProviderConnection(ContentProviderRecord _provider, ProcessRecord _client) {
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provider = _provider;
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client = _client;
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}
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public String toString() {
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StringBuilder sb = new StringBuilder(128);
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sb.append("ContentProviderConnection{");
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toShortString(sb);
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sb.append('}');
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return sb.toString();
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}
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public String toShortString() {
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StringBuilder sb = new StringBuilder(128);
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toShortString(sb);
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return sb.toString();
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}
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public String toClientString() {
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StringBuilder sb = new StringBuilder(128);
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toClientString(sb);
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return sb.toString();
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}
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public void toShortString(StringBuilder sb) {
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sb.append(provider.toShortString());
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sb.append("->");
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toClientString(sb);
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}
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public void toClientString(StringBuilder sb) {
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sb.append(client.toShortString());
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sb.append(" s");
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sb.append(stableCount);
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sb.append("/");
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sb.append(numStableIncs);
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sb.append(" u");
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sb.append(unstableCount);
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sb.append("/");
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sb.append(numUnstableIncs);
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if (waiting) {
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sb.append(" WAITING");
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}
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if (dead) {
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sb.append(" DEAD");
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}
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}
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}
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