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-rw-r--r--core/java/android/app/ActivityThread.java324
1 files changed, 190 insertions, 134 deletions
diff --git a/core/java/android/app/ActivityThread.java b/core/java/android/app/ActivityThread.java
index f9896f7..303f81b 100644
--- a/core/java/android/app/ActivityThread.java
+++ b/core/java/android/app/ActivityThread.java
@@ -2734,8 +2734,9 @@ public final class ActivityThread {
CharSequence description;
}
- private class ProviderRefCount {
+ private static final class ProviderRefCount {
public int count;
+
ProviderRefCount(int pCount) {
count = pCount;
}
@@ -3988,16 +3989,14 @@ public final class ActivityThread {
buf.append(": ");
buf.append(cpi.name);
Log.i(TAG, buf.toString());
- IContentProvider cp = installProvider(context, null, cpi, false);
+ IContentProvider cp = installProvider(context, null, cpi,
+ false /*noisy*/, true /*noReleaseNeeded*/);
if (cp != null) {
IActivityManager.ContentProviderHolder cph =
- new IActivityManager.ContentProviderHolder(cpi);
+ new IActivityManager.ContentProviderHolder(cpi);
cph.provider = cp;
+ cph.noReleaseNeeded = true;
results.add(cph);
- // Don't ever unload this provider from the process.
- synchronized(mProviderMap) {
- mProviderRefCountMap.put(cp.asBinder(), new ProviderRefCount(10000));
- }
}
}
@@ -4008,26 +4007,22 @@ public final class ActivityThread {
}
}
- private IContentProvider getExistingProvider(Context context, String name) {
- synchronized(mProviderMap) {
- final ProviderClientRecord pr = mProviderMap.get(name);
- if (pr != null) {
- return pr.mProvider;
- }
- return null;
- }
- }
-
- private IContentProvider getProvider(Context context, String name) {
- IContentProvider existing = getExistingProvider(context, name);
- if (existing != null) {
- return existing;
+ public final IContentProvider acquireProvider(Context c, String name) {
+ IContentProvider provider = acquireExistingProvider(c, name);
+ if (provider != null) {
+ return provider;
}
+ // There is a possible race here. Another thread may try to acquire
+ // the same provider at the same time. When this happens, we want to ensure
+ // that the first one wins.
+ // Note that we cannot hold the lock while acquiring and installing the
+ // provider since it might take a long time to run and it could also potentially
+ // be re-entrant in the case where the provider is in the same process.
IActivityManager.ContentProviderHolder holder = null;
try {
holder = ActivityManagerNative.getDefault().getContentProvider(
- getApplicationThread(), name);
+ getApplicationThread(), name);
} catch (RemoteException ex) {
}
if (holder == null) {
@@ -4035,135 +4030,136 @@ public final class ActivityThread {
return null;
}
- IContentProvider prov = installProvider(context, holder.provider,
- holder.info, true);
- //Slog.i(TAG, "noReleaseNeeded=" + holder.noReleaseNeeded);
- if (holder.noReleaseNeeded || holder.provider == null) {
- // We are not going to release the provider if it is an external
- // provider that doesn't care about being released, or if it is
- // a local provider running in this process.
- //Slog.i(TAG, "*** NO RELEASE NEEDED");
- synchronized(mProviderMap) {
- mProviderRefCountMap.put(prov.asBinder(), new ProviderRefCount(10000));
+ // Install provider will increment the reference count for us, and break
+ // any ties in the race.
+ provider = installProvider(c, holder.provider, holder.info,
+ true /*noisy*/, holder.noReleaseNeeded);
+ if (holder.provider != null && provider != holder.provider) {
+ if (localLOGV) {
+ Slog.v(TAG, "acquireProvider: lost the race, releasing extraneous "
+ + "reference to the content provider");
+ }
+ try {
+ ActivityManagerNative.getDefault().removeContentProvider(
+ getApplicationThread(), name);
+ } catch (RemoteException ex) {
}
}
- return prov;
- }
-
- public final IContentProvider acquireProvider(Context c, String name) {
- IContentProvider provider = getProvider(c, name);
- if(provider == null)
- return null;
- IBinder jBinder = provider.asBinder();
- synchronized(mProviderMap) {
- ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
- if(prc == null) {
- mProviderRefCountMap.put(jBinder, new ProviderRefCount(1));
- } else {
- prc.count++;
- } //end else
- } //end synchronized
return provider;
}
public final IContentProvider acquireExistingProvider(Context c, String name) {
- IContentProvider provider = getExistingProvider(c, name);
- if(provider == null)
- return null;
- IBinder jBinder = provider.asBinder();
- synchronized(mProviderMap) {
+ synchronized (mProviderMap) {
+ ProviderClientRecord pr = mProviderMap.get(name);
+ if (pr == null) {
+ return null;
+ }
+
+ IContentProvider provider = pr.mProvider;
+ IBinder jBinder = provider.asBinder();
+
+ // Only increment the ref count if we have one. If we don't then the
+ // provider is not reference counted and never needs to be released.
ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
- if(prc == null) {
- mProviderRefCountMap.put(jBinder, new ProviderRefCount(1));
- } else {
- prc.count++;
- } //end else
- } //end synchronized
- return provider;
+ if (prc != null) {
+ prc.count += 1;
+ if (prc.count == 1) {
+ if (localLOGV) {
+ Slog.v(TAG, "acquireExistingProvider: "
+ + "snatched provider from the jaws of death");
+ }
+ // Because the provider previously had a reference count of zero,
+ // it was scheduled to be removed. Cancel that.
+ mH.removeMessages(H.REMOVE_PROVIDER, provider);
+ }
+ }
+ return provider;
+ }
}
public final boolean releaseProvider(IContentProvider provider) {
if(provider == null) {
return false;
}
+
IBinder jBinder = provider.asBinder();
- synchronized(mProviderMap) {
+ synchronized (mProviderMap) {
ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
- if(prc == null) {
- if(localLOGV) Slog.v(TAG, "releaseProvider::Weird shouldn't be here");
+ if (prc == null) {
+ // The provider has no ref count, no release is needed.
return false;
- } else {
- prc.count--;
- if(prc.count == 0) {
- // Schedule the actual remove asynchronously, since we
- // don't know the context this will be called in.
- // TODO: it would be nice to post a delayed message, so
- // if we come back and need the same provider quickly
- // we will still have it available.
- Message msg = mH.obtainMessage(H.REMOVE_PROVIDER, provider);
- mH.sendMessage(msg);
- } //end if
- } //end else
- } //end synchronized
- return true;
+ }
+
+ if (prc.count == 0) {
+ if (localLOGV) Slog.v(TAG, "releaseProvider: ref count already 0, how?");
+ return false;
+ }
+
+ prc.count -= 1;
+ if (prc.count == 0) {
+ // Schedule the actual remove asynchronously, since we don't know the context
+ // this will be called in.
+ // TODO: it would be nice to post a delayed message, so
+ // if we come back and need the same provider quickly
+ // we will still have it available.
+ Message msg = mH.obtainMessage(H.REMOVE_PROVIDER, provider);
+ mH.sendMessage(msg);
+ }
+ return true;
+ }
}
final void completeRemoveProvider(IContentProvider provider) {
IBinder jBinder = provider.asBinder();
- String name = null;
+ String remoteProviderName = null;
synchronized(mProviderMap) {
ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
- if(prc != null && prc.count == 0) {
- mProviderRefCountMap.remove(jBinder);
- //invoke removeProvider to dereference provider
- name = removeProviderLocked(provider);
+ if (prc == null) {
+ // Either no release is needed (so we shouldn't be here) or the
+ // provider was already released.
+ if (localLOGV) Slog.v(TAG, "completeRemoveProvider: release not needed");
+ return;
+ }
+
+ if (prc.count != 0) {
+ // There was a race! Some other client managed to acquire
+ // the provider before the removal was completed.
+ // Abort the removal. We will do it later.
+ if (localLOGV) Slog.v(TAG, "completeRemoveProvider: lost the race, "
+ + "provider still in use");
+ return;
+ }
+
+ mProviderRefCountMap.remove(jBinder);
+
+ Iterator<ProviderClientRecord> iter = mProviderMap.values().iterator();
+ while (iter.hasNext()) {
+ ProviderClientRecord pr = iter.next();
+ IBinder myBinder = pr.mProvider.asBinder();
+ if (myBinder == jBinder) {
+ iter.remove();
+ if (pr.mLocalProvider == null) {
+ myBinder.unlinkToDeath(pr, 0);
+ if (remoteProviderName == null) {
+ remoteProviderName = pr.mName;
+ }
+ }
+ }
}
}
-
- if (name != null) {
+
+ if (remoteProviderName != null) {
try {
- if(localLOGV) Slog.v(TAG, "removeProvider::Invoking " +
- "ActivityManagerNative.removeContentProvider(" + name);
+ if (localLOGV) {
+ Slog.v(TAG, "removeProvider: Invoking ActivityManagerNative."
+ + "removeContentProvider(" + remoteProviderName + ")");
+ }
ActivityManagerNative.getDefault().removeContentProvider(
- getApplicationThread(), name);
+ getApplicationThread(), remoteProviderName);
} catch (RemoteException e) {
//do nothing content provider object is dead any way
- } //end catch
- }
- }
-
- public final String removeProviderLocked(IContentProvider provider) {
- if (provider == null) {
- return null;
+ }
}
- IBinder providerBinder = provider.asBinder();
-
- String name = null;
-
- // remove the provider from mProviderMap
- Iterator<ProviderClientRecord> iter = mProviderMap.values().iterator();
- while (iter.hasNext()) {
- ProviderClientRecord pr = iter.next();
- IBinder myBinder = pr.mProvider.asBinder();
- if (myBinder == providerBinder) {
- //find if its published by this process itself
- if(pr.mLocalProvider != null) {
- if(localLOGV) Slog.i(TAG, "removeProvider::found local provider returning");
- return name;
- }
- if(localLOGV) Slog.v(TAG, "removeProvider::Not local provider Unlinking " +
- "death recipient");
- //content provider is in another process
- myBinder.unlinkToDeath(pr, 0);
- iter.remove();
- //invoke remove only once for the very first name seen
- if(name == null) {
- name = pr.mName;
- }
- } //end if myBinder
- } //end while iter
-
- return name;
}
final void removeDeadProvider(String name, IContentProvider provider) {
@@ -4179,8 +4175,23 @@ public final class ActivityThread {
}
}
+ /**
+ * Installs the provider.
+ *
+ * Providers that are local to the process or that come from the system server
+ * may be installed permanently which is indicated by setting noReleaseNeeded to true.
+ * Other remote providers are reference counted. The initial reference count
+ * for all reference counted providers is one. Providers that are not reference
+ * counted do not have a reference count (at all).
+ *
+ * This method detects when a provider has already been installed. When this happens,
+ * it increments the reference count of the existing provider (if appropriate)
+ * and returns the existing provider. This can happen due to concurrent
+ * attempts to acquire the same provider.
+ */
private IContentProvider installProvider(Context context,
- IContentProvider provider, ProviderInfo info, boolean noisy) {
+ IContentProvider provider, ProviderInfo info,
+ boolean noisy, boolean noReleaseNeeded) {
ContentProvider localProvider = null;
if (provider == null) {
if (noisy) {
@@ -4238,24 +4249,69 @@ public final class ActivityThread {
}
synchronized (mProviderMap) {
- // Cache the pointer for the remote provider.
+ // There is a possibility that this thread raced with another thread to
+ // add the provider. If we find another thread got there first then we
+ // just get out of the way and return the original provider.
+ IBinder jBinder = provider.asBinder();
String names[] = PATTERN_SEMICOLON.split(info.authority);
- for (int i=0; i<names.length; i++) {
- ProviderClientRecord pr = new ProviderClientRecord(names[i], provider,
- localProvider);
- try {
- provider.asBinder().linkToDeath(pr, 0);
+ for (int i = 0; i < names.length; i++) {
+ ProviderClientRecord pr = mProviderMap.get(names[i]);
+ if (pr != null) {
+ if (localLOGV) {
+ Slog.v(TAG, "installProvider: lost the race, "
+ + "using existing named provider");
+ }
+ provider = pr.mProvider;
+ } else {
+ pr = new ProviderClientRecord(names[i], provider, localProvider);
+ if (localProvider == null) {
+ try {
+ jBinder.linkToDeath(pr, 0);
+ } catch (RemoteException e) {
+ // Provider already dead. Bail out of here without making
+ // any changes to the provider map or other data structures.
+ return null;
+ }
+ }
mProviderMap.put(names[i], pr);
- } catch (RemoteException e) {
- return null;
}
}
+
if (localProvider != null) {
- mLocalProviders.put(provider.asBinder(),
- new ProviderClientRecord(null, provider, localProvider));
+ ProviderClientRecord pr = mLocalProviders.get(jBinder);
+ if (pr != null) {
+ if (localLOGV) {
+ Slog.v(TAG, "installProvider: lost the race, "
+ + "using existing local provider");
+ }
+ provider = pr.mProvider;
+ } else {
+ pr = new ProviderClientRecord(null, provider, localProvider);
+ mLocalProviders.put(jBinder, pr);
+ }
}
- }
+ if (!noReleaseNeeded) {
+ ProviderRefCount prc = mProviderRefCountMap.get(jBinder);
+ if (prc != null) {
+ if (localLOGV) {
+ Slog.v(TAG, "installProvider: lost the race, incrementing ref count");
+ }
+ prc.count += 1;
+ if (prc.count == 1) {
+ if (localLOGV) {
+ Slog.v(TAG, "installProvider: "
+ + "snatched provider from the jaws of death");
+ }
+ // Because the provider previously had a reference count of zero,
+ // it was scheduled to be removed. Cancel that.
+ mH.removeMessages(H.REMOVE_PROVIDER, provider);
+ }
+ } else {
+ mProviderRefCountMap.put(jBinder, new ProviderRefCount(1));
+ }
+ }
+ }
return provider;
}
generated by cgit v1.1 at 2025-11-14 23:45:33 +0000